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<rfc category="std" docName="draft-wu-l3sm-rfc8049bis-04" ipr="trust200902" obsoletes="8049">

  <front>

    <title abbrev="YANG Data Model for L3VPN Service Delivery">YANG Data Model for L3VPN Service Delivery</title>

    <author fullname="Qin Wu" initials="Q." surname="Wu" role="editor">
      <organization abbrev="Huawei">Huawei Technologies</organization>

      <address>
        <email>bill.wu@huawei.com</email>
      </address>
    </author>

    <author fullname="Stephane Litkowski" initials="S." surname="Litkowski">
      <organization abbrev="Orange">Orange Business Services</organization>

      <address>
        <email>stephane.litkowski@orange.com</email>
      </address>
    </author>

    <author fullname="Luis Tomotaki" initials="L." surname="Tomotaki">
      <organization>Verizon</organization>

      <address>
        <email>luis.tomotaki@verizon.com</email>
      </address>
    </author>

    <author fullname="Kenichi Ogaki" initials="K." surname="Ogaki">
      <organization>KDDI Corporation</organization>

      <address>
        <email>ke-oogaki@kddi.com</email>
      </address>
    </author>

    <date year="2017"/>

    <area>Operations and Management</area>

    <keyword>YANG</keyword>
    <keyword>L3VPN</keyword>
    <keyword>Data Model</keyword>
    <keyword>Service Model</keyword>

    <abstract>
      <t>This document defines a YANG data model that can be used for
         communication between customers and network operators and to deliver
         a Layer 3 provider-provisioned VPN service.  This document is limited
         to BGP PE-based VPNs as described in RFCs 4026, 4110, and 4364.  This
         model is intended to be instantiated at the management system to
         deliver the overall service.  It is not a configuration model to be
         used directly on network elements.  This model provides an abstracted
         view of the Layer 3 IP VPN service configuration components.  It will
         be up to the management system to take this model as input and use
         specific configuration models to configure the different network
         elements to deliver the service.  How the configuration of network
         elements is done is out of scope for this document.</t>

      <t>If approved, this document obsoletes RFC 8049.  The changes are a
         series of small fixes to the YANG module, and some clarifications to
         the text.</t>
    </abstract>
  </front>

  <middle>

    <section anchor="introduction" title="Introduction">

      <t>This document defines a Layer 3 VPN service data model written in
         YANG.  The model defines service configuration elements that can be
         used in communication protocols between customers and network
         operators.  Those elements can also be used as input to automated
         control and configuration applications.</t>

      <t>If approved, this document obsoletes <xref target="RFC8049" />.  
	     The changes are a series of small fixes to the YANG module, 
		 and some clarifications to the text.The changes are listed 
		 in Section 1.4.</t>

      <section anchor="terms" title="Terminology">

        <t>The following terms are defined in <xref target="RFC6241" /> 
		   and are not redefined here:
           <list style="symbols">
             <t>client</t>
             <t>configuration data</t>
             <t>server</t>
             <t>state data</t>
           </list></t>

        <t>The following terms are defined in <xref target="RFC7950" /> 
		   and are not redefined here:
           <list style="symbols">
             <t>augment</t>
             <t>data model</t>
             <t>data node</t>
           </list></t>

        <t>The terminology for describing YANG data models is found 
		   in <xref target="RFC7950" />.</t>

        <t>This document presents some configuration examples using 
		   XML representation.</t>

      </section>

      <section anchor="lang" title="Requirements Language">

        <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
           "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
           document are to be interpreted as described in <xref target="RFC2119" />.
		</t>

      </section>

      <section anchor="trees" title="Tree Diagrams">

        <t>A simplified graphical representation of the data model is presented
           in <xref target="design" />.</t>

        <t>The meanings of the symbols in these diagrams are as follows:

           <list style="symbols">

              <t>Brackets "[" and "]" enclose list keys.</t>

              <t>Curly braces "{" and "}" contain names of optional features that
                 make the corresponding node conditional.</t>

              <t>Abbreviations before data node names: "rw" means configuration
                 data (read-write), and "ro" means state data (read-only).</t>

              <t>Symbols after data node names: "?" means an optional node, and "*"
                 denotes a "list" or "leaf-list".</t>

              <t>Parentheses enclose choice and case nodes, and case nodes are also
                 marked with a colon (":").</t>

              <t>Ellipsis ("...") stands for contents of subtrees that are not
                 shown.</t>

           </list></t>

      </section>
	  
      <section title="Summary of Changes from RFC 8049">
        <t>This document revises and obsoletes L3VPN Service Model [RFC8049] ,
        drawing on insights gained from L3VPN Service Model deployments and on
        feedback from the community. The major changes are: <list
            style="symbols">
            <t>Change type from 16-bit integer to string for the leaf id 
			under "qos-classification-policy" container.</t>

            <t>Stick to using ordered-by user and remove inefficiency to map
            service model sequence number to device model sequence number.</t>

            <t>Remove mandating the use of deviations and add "if-feature
            target-sites" under the leaf-list target-sites in section 6.12.2.</t>

            <t>RFC2119 language changes on operation of the management
            system in Section 6.6,3rd paragraph,Section 6.6.5 and 
			section 7.</t>

            <t>Fix incomplete description statements.</t>

            <t>Add YANG statement to check that slaac parameters are used only
            for IPv6.</t>

            <t>Fix strange wording in the section 6.11.7.</t>

            <t>Change the use of the absolute paths to the use of relative
            paths in the "must" statement or "path" statement for vpn-policy-id
		    leaf node, management container, location leaf node, devices container, 
			location case, location-reference leaf, device case, device-reference
            leaf to make configuration is only applicable to the current sites. 
			</t>
			
			<t>Change "must" statement to "when" statement for management container
			device container. </t>

            <t>Fix optional parameter issues by adding a default or
            description for others or make some of them mandatory.</t>
			
			<t>Define new grouping vpn-profile-cfg for all the identifiers provided
			by SP to the customer. The identifiers include cloud-identifier,
			std-qos-profile, OAM profile-name, and provider-profile for encryption.
			</t>
			
			<t>Add in the XPATH string representation of identityrefs and remove 
			unqualified name. Change from YANG 1.0 Support to YANG 1.1 Support.</t>
			
			<t>Remove "when" statement from leaf nat44-customer-address.</t>
			
			<t> Fixed broken example and Add mandatory element in the examples. </t>
			
			<t>Remove redundant parameters in the cloud access.</t>
				
			<t>Specify provider address and a list of start-end addresses from 
			provider address for DHCP case. </t>
			
			<t>Add a few text to clarify what the site is in section 6.3.</t>
			
			<t>Add multi-filter and multi-VPN per entry support for VPN policy.</t>
			
			<t>Modify description for svc-input-bandwidth leaf and 
			svc-output-bandwidth leaf to make it consistent with 
			the text in section 6.12.1.</t>
			
			<t>Clarify the rational of the model in the section 5.</t>
			
			<t>Add text to clarify the way to achieve Per-VPN QoS policy.</t>
          </list></t>
      </section>
	  
    </section>

    <section anchor="acronyms" title="Acronyms">

      <t>AAA: Authentication, Authorization, and Accounting.</t>

      <t>ACL: Access Control List.</t>

      <t>ADSL: Asymmetric DSL.</t>

      <t>AH: Authentication Header.</t>

      <t>AS: Autonomous System.</t>

      <t>ASBR: Autonomous System Border Router.</t>

      <t>ASM: Any-Source Multicast.</t>

      <t>BAS: Broadband Access Switch.</t>

      <t>BFD: Bidirectional Forwarding Detection.</t>

      <t>BGP: Border Gateway Protocol.</t>

      <t>BSR: Bootstrap Router.</t>

      <t>CE: Customer Edge.</t>

      <t>CLI: Command Line Interface.</t>

      <t>CsC: Carriers&apos; Carriers.</t>

      <t>CSP: Cloud Service Provider.</t>

      <t>DHCP: Dynamic Host Configuration Protocol.</t>

      <t>DSLAM: Digital Subscriber Line Access Multiplexer.</t>

      <t>ESP: Encapsulating Security Payload.</t>

      <t>GRE: Generic Routing Encapsulation.</t>

      <t>IGMP: Internet Group Management Protocol.</t>

      <t>LAN: Local Area Network.</t>

      <t>MLD: Multicast Listener Discovery.</t>

      <t>MTU: Maximum Transmission Unit.</t>

      <t>NAT: Network Address Translation.</t>

      <t>NETCONF: Network Configuration Protocol.</t>

      <t>NNI: Network-to-Network Interface.</t>

      <t>OAM: Operations, Administration, and Maintenance.</t>

      <t>OSPF: Open Shortest Path First.</t>

      <t>OSS: Operations Support System.</t>

      <t>PE: Provider Edge.</t>

      <t>PIM: Protocol Independent Multicast.</t>

      <t>POP: Point of Presence.</t>

      <t>QoS: Quality of Service.</t>

      <t>RD: Route Distinguisher.</t>

      <t>RIP: Routing Information Protocol.</t>

      <t>RP: Rendezvous Point.</t>

      <t>RT: Route Target.</t>

      <t>SFTP: Secure FTP.</t>

      <t>SLA: Service Level Agreement.</t>

      <t>SLAAC: Stateless Address Autoconfiguration.</t>

      <t>SP: Service Provider.</t>

      <t>SPT: Shortest Path Tree.</t>

      <t>SSM: Source-Specific Multicast.</t>

      <t>VM: Virtual Machine.</t>

      <t>VPN: Virtual Private Network.</t>

      <t>VRF: VPN Routing and Forwarding.</t>

      <t>VRRP: Virtual Router Redundancy Protocol.</t>

    </section>

    <section anchor="definitions" title="Definitions">

      <t>Customer Edge (CE) Device: A CE is equipment dedicated to a
         particular customer; it is directly connected (at Layer 3) to one or
         more PE devices via attachment circuits.  A CE is usually located at
         the customer premises and is usually dedicated to a single VPN,
         although it may support multiple VPNs if each one has separate
         attachment circuits.</t>

      <t>Provider Edge (PE) Device: A PE is equipment managed by the SP; it
         can support multiple VPNs for different customers and is directly
         connected (at Layer 3) to one or more CE devices via attachment
         circuits.  A PE is usually located at an SP point of presence (POP)
         and is managed by the SP.</t>

      <t>PE-Based VPNs: The PE devices know that certain traffic is VPN
         traffic.  They forward the traffic (through tunnels) based on the
         destination IP address of the packet and, optionally, based on other
         information in the IP header of the packet.  The PE devices are
         themselves the tunnel endpoints.  The tunnels may make use of various
         encapsulations to send traffic over the SP network (such as, but not
         restricted to, GRE, IP-in-IP, IPsec, or MPLS tunnels).</t>

    </section>

    <section anchor="l3vpnSM" title="Layer 3 IP VPN Service Model">

      <t>A Layer 3 IP VPN service is a collection of sites that are authorized
         to exchange traffic between each other over a shared IP
         infrastructure.  This Layer 3 VPN service model aims at providing a
         common understanding of how the corresponding IP VPN service is to be
         deployed over the shared infrastructure.  This service model is
         limited to BGP PE-based VPNs as described in <xref target="RFC4026" />,
         <xref target="RFC4110" />, and <xref target="RFC4364" />.</t>

    </section>

    <section anchor="usage" title="Service Data Model Usage">

      <figure>
        <artwork align="center">
          <![CDATA[
             l3vpn-svc |
               Model   |
                       |
                +------------------+         +-----+
                |   Orchestration  | < --- > | OSS |
                +------------------+         +-----+
                   |            |
           +----------------+   |
           | Config manager |   |
           +----------------+   |
                   |            |
                   | NETCONF/CLI ...
                   |            |
     +------------------------------------------------+
                          Network

                        +++++++
                        + AAA +
                        +++++++

++++++++   Bearer    ++++++++           ++++++++      ++++++++
+ CE A + ----------- + PE A +           + PE B + ---- + CE B +
++++++++  Connection ++++++++           ++++++++      ++++++++

           Site A                               Site B
          ]]>
        </artwork>
      </figure>

      <t>The idea of the L3 IP VPN service model is to propose an abstracted
         interface between customers and network operators to manage
         configuration of components of an L3VPN service. The model is
         intended to be used in a mode where the network operator's system is
         the server and the customer's system is the client. A typical scenario
		 would be to use this model as an input for an orchestration layer 
		 that will be responsible for translating it to an orchestrated 
		 configuration of network elements that will be part of the service. 
		 The network elements can be routers but can also be servers (like 
		 AAA); the network&apos;s  configuration is not limited to these 
		 examples. The configuration of network elements can be done via the 
		 CLI, NETCONF/RESTCONF <xref target="RFC6241"/> <xref target="RFC8040" /> 
		 coupled with YANG data models of a specific configuration (BGP, VRF, 
		 BFD, etc.), or some other technique, as preferred by the operator.</t>

      <t>The usage of this service model is not limited to this example; it
         can be used by any component of the management system but not
         directly by network elements.</t>

    </section>

    <section anchor="design" title="Design of the Data Model">

      <t>The YANG module is divided into two main containers: "vpn-services"
         and "sites".</t>

      <t>The "vpn-service" list under the vpn-services container defines
         global parameters for the VPN service for a specific customer.</t>

      <t>A "site" is composed of at least one "site-network-access" and, in
         the case of multihoming, may have multiple site-network-access
         points.  The site-network-access attachment is done through a
         "bearer" with an "ip-connection" on top.  The bearer refers to
         properties of the attachment that are below Layer 3, while the
         connection refers to properties oriented to the Layer 3 protocol.
         The bearer may be allocated dynamically by the SP, and the customer
         may provide some constraints or parameters to drive the placement of
         the access.</t>

      <t>Authorization of traffic exchange is done through what we call a VPN
         policy or VPN service topology defining routing exchange rules
         between sites.</t>

      <t>The figure below describes the overall structure of the YANG module:</t>

      <figure>
        <artwork align="center">
          <![CDATA[
module: ietf-l3vpn-svc
   +--rw l3vpn-svc
      +--rw vpn-profiles
      |  +--rw valid-provider-identifiers
      |     +--rw cloud-identifier* [id] {cloud-access}?
      |     |  +--rw id    string
      |     +--rw encryption-profile-identifier* [id]
      |     |  +--rw id    string
      |     +--rw qos-profile-identifier* [id]
      |     |  +--rw id    string
      |     +--rw bfd-profile-identifier* [id]
      |        +--rw id    string
      +--rw vpn-services
      |  +--rw vpn-service* [vpn-id]
      |     +--rw vpn-id                  svc-id
      |     +--rw customer-name?          string
      |     +--rw vpn-service-topology?   identityref
      |     +--rw cloud-accesses {cloud-access}?
      |     |  +--rw cloud-access* [cloud-identifier]
      |     |     +--rw cloud-identifier       -> /l3vpn-svc/vpn-profiles/valid-provider-identifiers/cloud-identifier/id
      |     |     +--rw (list-flavor)?
      |     |     |  +--:(permit-any)
      |     |     |  |  +--rw permit-any?            empty
      |     |     |  +--:(deny-any-except)
      |     |     |  |  +--rw permit-site*           -> /l3vpn-svc/sites/site/site-id
      |     |     |  +--:(permit-any-except)
      |     |     |     +--rw deny-site*             -> /l3vpn-svc/sites/site/site-id
      |     |     +--rw address-translation
      |     |        +--rw nat44
      |     |           +--rw enabled?                  boolean
      |     |           +--rw nat44-customer-address?   inet:ipv4-address
      |     +--rw multicast {multicast}?
      |     |  +--rw enabled?                 boolean
      |     |  +--rw customer-tree-flavors
      |     |  |  +--rw tree-flavor*   identityref
      |     |  +--rw rp
      |     |     +--rw rp-group-mappings
      |     |     |  +--rw rp-group-mapping* [id]
      |     |     |     +--rw id                  uint16
      |     |     |     +--rw provider-managed
      |     |     |     |  +--rw enabled?                    boolean
      |     |     |     |  +--rw rp-redundancy?              boolean
      |     |     |     |  +--rw optimal-traffic-delivery?   boolean
      |     |     |     +--rw rp-address          inet:ip-address
      |     |     |     +--rw groups
      |     |     |        +--rw group* [id]
      |     |     |           +--rw id               uint16
      |     |     |           +--rw (group-format)
      |     |     |              +--:(singleaddress)
      |     |     |              |  +--rw group-address?   inet:ip-address
      |     |     |              +--:(startend)
      |     |     |                 +--rw group-start?     inet:ip-address
      |     |     |                 +--rw group-end?       inet:ip-address
      |     |     +--rw rp-discovery
      |     |        +--rw rp-discovery-type?   identityref
      |     |        +--rw bsr-candidates
      |     |           +--rw bsr-candidate-address*   inet:ip-address
      |     +--rw carrierscarrier?        boolean {carrierscarrier}?
      |     +--rw extranet-vpns {extranet-vpn}?
      |        +--rw extranet-vpn* [vpn-id]
      |           +--rw vpn-id              svc-id
      |           +--rw local-sites-role?   identityref
      +--rw sites
         +--rw site* [site-id]
            +--rw site-id                  svc-id
            +--rw requested-site-start?    yang:date-and-time
            +--rw requested-site-stop?     yang:date-and-time
            +--rw locations
            |  +--rw location* [location-id]
            |     +--rw location-id     svc-id
            |     +--rw address?        string
            |     +--rw postal-code?    string
            |     +--rw state?          string
            |     +--rw city?           string
            |     +--rw country-code?   string
            +--rw devices
            |  +--rw device* [device-id]
            |     +--rw device-id     svc-id
            |     +--rw location      -> ../../../locations/location/location-id
            |     +--rw management
            |        +--rw address-family?   address-family
            |        +--rw address?          inet:ip-address
            +--rw site-diversity {site-diversity}?
            |  +--rw groups
            |     +--rw group* [group-id]
            |        +--rw group-id    string
            +--rw management
            |  +--rw type    identityref
            +--rw vpn-policies
            |  +--rw vpn-policy* [vpn-policy-id]
            |     +--rw vpn-policy-id    svc-id
            |     +--rw entries* [id]
            |        +--rw id         svc-id
            |        +--rw filters
            |        |  +--rw filter* [type]
            |        |     +--rw type               identityref
            |        |     +--rw ipv4-lan-prefix*   inet:ipv4-prefix {ipv4}?
            |        |     +--rw lan-tag*           string {lan-tag}?
            |        |     +--rw ipv6-lan-prefix*   inet:ipv6-prefix {ipv6}?
            |        +--rw vpn* [vpn-id]
            |           +--rw vpn-id       -> /l3vpn-svc/vpn-services/vpn-service/vpn-id
            |           +--rw site-role?   identityref
            +--rw site-vpn-flavor?         identityref
            +--rw maximum-routes
            |  +--rw address-family* [af]
            |     +--rw af                address-family
            |     +--rw maximum-routes?   uint32
            +--rw security
            |  +--rw authentication
            |  +--rw encryption {encryption}?
            |     +--rw enabled?              boolean
            |     +--rw layer?                enumeration
            |     +--rw encryption-profile
            |        +--rw (profile)?
            |           +--:(provider-profile)
            |           |  +--rw profile-name?    -> /l3vpn-svc/vpn-profiles/valid-provider-identifiers/encryption-profile-identifier/id
            |           +--:(customer-profile)
            |              +--rw algorithm?       string
            |              +--rw (key-type)?
            |                 +--:(psk)
            |                    +--rw preshared-key?   string
            +--rw service
            |  +--rw qos {qos}?
            |  |  +--rw qos-classification-policy
            |  |  |  +--rw rule* [id]
            |  |  |     +--rw id                   string
            |  |  |     +--rw (match-type)?
            |  |  |     |  +--:(match-flow)
            |  |  |     |  |  +--rw match-flow
            |  |  |     |  |     +--rw dscp?                inet:dscp
            |  |  |     |  |     +--rw dot1p?               uint8
            |  |  |     |  |     +--rw ipv4-src-prefix?     inet:ipv4-prefix
            |  |  |     |  |     +--rw ipv6-src-prefix?     inet:ipv6-prefix
            |  |  |     |  |     +--rw ipv4-dst-prefix?     inet:ipv4-prefix
            |  |  |     |  |     +--rw ipv6-dst-prefix?     inet:ipv6-prefix
            |  |  |     |  |     +--rw l4-src-port?         inet:port-number
            |  |  |     |  |     +--rw target-sites*        svc-id {target-sites}?
            |  |  |     |  |     +--rw l4-src-port-range
            |  |  |     |  |     |  +--rw lower-port?   inet:port-number
            |  |  |     |  |     |  +--rw upper-port?   inet:port-number
            |  |  |     |  |     +--rw l4-dst-port?         inet:port-number
            |  |  |     |  |     +--rw l4-dst-port-range
            |  |  |     |  |     |  +--rw lower-port?   inet:port-number
            |  |  |     |  |     |  +--rw upper-port?   inet:port-number
            |  |  |     |  |     +--rw protocol-field?      union
            |  |  |     |  +--:(match-application)
            |  |  |     |     +--rw match-application?   identityref
            |  |  |     +--rw target-class-id?     string
            |  |  +--rw qos-profile
            |  |     +--rw (qos-profile)?
            |  |        +--:(standard)
            |  |        |  +--rw profile?   -> /l3vpn-svc/vpn-profiles/valid-provider-identifiers/qos-profile-identifier/id
            |  |        +--:(custom)
            |  |           +--rw classes {qos-custom}?
            |  |              +--rw class* [class-id]
            |  |                 +--rw class-id      string
            |  |                 +--rw direction?    identityref
            |  |                 +--rw rate-limit?   uint8
            |  |                 +--rw latency
            |  |                 |  +--rw (flavor)?
            |  |                 |     +--:(lowest)
            |  |                 |     |  +--rw use-lowest-latency?   empty
            |  |                 |     +--:(boundary)
            |  |                 |        +--rw latency-boundary?     uint16
            |  |                 +--rw jitter
            |  |                 |  +--rw (flavor)?
            |  |                 |     +--:(lowest)
            |  |                 |     |  +--rw use-lowest-jitter?   empty
            |  |                 |     +--:(boundary)
            |  |                 |        +--rw latency-boundary?    uint32
            |  |                 +--rw bandwidth
            |  |                    +--rw guaranteed-bw-percent    uint8
            |  |                    +--rw end-to-end?              empty
            |  +--rw carrierscarrier {carrierscarrier}?
            |  |  +--rw signalling-type?   enumeration
            |  +--rw multicast {multicast}?
            |     +--rw multicast-site-type?        enumeration
            |     +--rw multicast-address-family
            |     |  +--rw ipv4?   boolean {ipv4}?
            |     |  +--rw ipv6?   boolean {ipv6}?
            |     +--rw protocol-type?              enumeration
            +--rw traffic-protection {fast-reroute}?
            |  +--rw enabled?   boolean
            +--rw routing-protocols
            |  +--rw routing-protocol* [type]
            |     +--rw type      identityref
            |     +--rw ospf {rtg-ospf}?
            |     |  +--rw address-family*   address-family
            |     |  +--rw area-address      yang:dotted-quad
            |     |  +--rw metric?           uint16
            |     |  +--rw sham-links {rtg-ospf-sham-link}?
            |     |     +--rw sham-link* [target-site]
            |     |        +--rw target-site    svc-id
            |     |        +--rw metric?        uint16
            |     +--rw bgp {rtg-bgp}?
            |     |  +--rw autonomous-system    uint32
            |     |  +--rw address-family*      address-family
            |     +--rw static
            |     |  +--rw cascaded-lan-prefixes
            |     |     +--rw ipv4-lan-prefixes* [lan next-hop] {ipv4}?
            |     |     |  +--rw lan         inet:ipv4-prefix
            |     |     |  +--rw lan-tag?    string
            |     |     |  +--rw next-hop    inet:ipv4-address
            |     |     +--rw ipv6-lan-prefixes* [lan next-hop] {ipv6}?
            |     |        +--rw lan         inet:ipv6-prefix
            |     |        +--rw lan-tag?    string
            |     |        +--rw next-hop    inet:ipv6-address
            |     +--rw rip {rtg-rip}?
            |     |  +--rw address-family*   address-family
            |     +--rw vrrp {rtg-vrrp}?
            |        +--rw address-family*   address-family
            +--ro actual-site-start?       yang:date-and-time
            +--ro actual-site-stop?        yang:date-and-time
            +--rw site-network-accesses
               +--rw site-network-access* [site-network-access-id]
                  +--rw site-network-access-id      svc-id
                  +--rw site-network-access-type?   identityref
                  +--rw (location-flavor)
                  |  +--:(location)
                  |  |  +--rw location-reference?         -> ../../../locations/location/location-id
                  |  +--:(device)
                  |     +--rw device-reference?           -> ../../../devices/device/device-id
                  +--rw access-diversity {site-diversity}?
                  |  +--rw groups
                  |  |  +--rw group* [group-id]
                  |  |     +--rw group-id    string
                  |  +--rw constraints
                  |     +--rw constraint* [constraint-type]
                  |        +--rw constraint-type    identityref
                  |        +--rw target
                  |           +--rw (target-flavor)?
                  |              +--:(id)
                  |              |  +--rw group* [group-id]
                  |              |     +--rw group-id    string
                  |              +--:(all-accesses)
                  |              |  +--rw all-other-accesses?   empty
                  |              +--:(all-groups)
                  |                 +--rw all-other-groups?     empty
                  +--rw bearer
                  |  +--rw requested-type {requested-type}?
                  |  |  +--rw requested-type?   string
                  |  |  +--rw strict?           boolean
                  |  +--rw always-on?          boolean {always-on}?
                  |  +--rw bearer-reference?   string {bearer-reference}?
                  +--rw ip-connection
                  |  +--rw ipv4 {ipv4}?
                  |  |  +--rw address-allocation-type?   identityref
                  |  |  +--rw provider-dhcp
                  |  |  |  +--rw provider-address?            inet:ipv4-address
                  |  |  |  +--rw mask?                        uint8
                  |  |  |  +--rw (address-assign)?
                  |  |  |     +--:(number)
                  |  |  |     |  +--rw number-of-dynamic-address?   uint8
                  |  |  |     +--:(explicit)
                  |  |  |        +--rw customer-addresses
                  |  |  |           +--rw address-group* [group-id]
                  |  |  |              +--rw group-id         string
                  |  |  |              +--rw start-address?   inet:ipv4-address
                  |  |  |              +--rw end-address?     inet:ipv4-address
                  |  |  +--rw dhcp-relay
                  |  |  |  +--rw provider-address?        inet:ipv4-address
                  |  |  |  +--rw mask?                    uint8
                  |  |  |  +--rw customer-dhcp-servers
                  |  |  |     +--rw server-ip-address*   inet:ipv4-address
                  |  |  +--rw addresses
                  |  |     +--rw provider-address?   inet:ipv4-address
                  |  |     +--rw customer-address?   inet:ipv4-address
                  |  |     +--rw mask?               uint8
                  |  +--rw ipv6 {ipv6}?
                  |  |  +--rw address-allocation-type?   identityref
                  |  |  +--rw provider-dhcp
                  |  |  |  +--rw provider-address?            inet:ipv6-address
                  |  |  |  +--rw mask?                        uint8
                  |  |  |  +--rw (address-assign)?
                  |  |  |     +--:(number)
                  |  |  |     |  +--rw number-of-dynamic-address?   uint8
                  |  |  |     +--:(explicit)
                  |  |  |        +--rw customer-addresses
                  |  |  |           +--rw address-group* [group-id]
                  |  |  |              +--rw group-id         string
                  |  |  |              +--rw start-address?   inet:ipv6-address
                  |  |  |              +--rw end-address?     inet:ipv6-address
                  |  |  +--rw dhcp-relay
                  |  |  |  +--rw provider-address?        inet:ipv6-address
                  |  |  |  +--rw mask?                    uint8
                  |  |  |  +--rw customer-dhcp-servers
                  |  |  |     +--rw server-ip-address*   inet:ipv6-address
                  |  |  +--rw addresses
                  |  |     +--rw provider-address?   inet:ipv6-address
                  |  |     +--rw customer-address?   inet:ipv6-address
                  |  |     +--rw mask?               uint8
                  |  +--rw oam
                  |     +--rw bfd {bfd}?
                  |        +--rw enabled?        boolean
                  |        +--rw (holdtime)?
                  |           +--:(fixed)
                  |           |  +--rw fixed-value?    uint32
                  |           +--:(profile)
                  |              +--rw profile-name?   -> /l3vpn-svc/vpn-profiles/valid-provider-identifiers/bfd-profile-identifier/id
                  +--rw security
                  |  +--rw authentication
                  |  +--rw encryption {encryption}?
                  |     +--rw enabled?              boolean
                  |     +--rw layer?                enumeration
                  |     +--rw encryption-profile
                  |        +--rw (profile)?
                  |           +--:(provider-profile)
                  |           |  +--rw profile-name?    -> /l3vpn-svc/vpn-profiles/valid-provider-identifiers/encryption-profile-identifier/id
                  |           +--:(customer-profile)
                  |              +--rw algorithm?       string
                  |              +--rw (key-type)?
                  |                 +--:(psk)
                  |                    +--rw preshared-key?   string
                  +--rw service
                  |  +--rw svc-input-bandwidth     uint64
                  |  +--rw svc-output-bandwidth    uint64
                  |  +--rw svc-mtu                 uint16
                  |  +--rw qos {qos}?
                  |  |  +--rw qos-classification-policy
                  |  |  |  +--rw rule* [id]
                  |  |  |     +--rw id                   string
                  |  |  |     +--rw (match-type)?
                  |  |  |     |  +--:(match-flow)
                  |  |  |     |  |  +--rw match-flow
                  |  |  |     |  |     +--rw dscp?                inet:dscp
                  |  |  |     |  |     +--rw dot1p?               uint8
                  |  |  |     |  |     +--rw ipv4-src-prefix?     inet:ipv4-prefix
                  |  |  |     |  |     +--rw ipv6-src-prefix?     inet:ipv6-prefix
                  |  |  |     |  |     +--rw ipv4-dst-prefix?     inet:ipv4-prefix
                  |  |  |     |  |     +--rw ipv6-dst-prefix?     inet:ipv6-prefix
                  |  |  |     |  |     +--rw l4-src-port?         inet:port-number
                  |  |  |     |  |     +--rw target-sites*        svc-id {target-sites}?
                  |  |  |     |  |     +--rw l4-src-port-range
                  |  |  |     |  |     |  +--rw lower-port?   inet:port-number
                  |  |  |     |  |     |  +--rw upper-port?   inet:port-number
                  |  |  |     |  |     +--rw l4-dst-port?         inet:port-number
                  |  |  |     |  |     +--rw l4-dst-port-range
                  |  |  |     |  |     |  +--rw lower-port?   inet:port-number
                  |  |  |     |  |     |  +--rw upper-port?   inet:port-number
                  |  |  |     |  |     +--rw protocol-field?      union
                  |  |  |     |  +--:(match-application)
                  |  |  |     |     +--rw match-application?   identityref
                  |  |  |     +--rw target-class-id?     string
                  |  |  +--rw qos-profile
                  |  |     +--rw (qos-profile)?
                  |  |        +--:(standard)
                  |  |        |  +--rw profile?   -> /l3vpn-svc/vpn-profiles/valid-provider-identifiers/qos-profile-identifier/id
                  |  |        +--:(custom)
                  |  |           +--rw classes {qos-custom}?
                  |  |              +--rw class* [class-id]
                  |  |                 +--rw class-id      string
                  |  |                 +--rw direction?    identityref
                  |  |                 +--rw rate-limit?   uint8
                  |  |                 +--rw latency
                  |  |                 |  +--rw (flavor)?
                  |  |                 |     +--:(lowest)
                  |  |                 |     |  +--rw use-lowest-latency?   empty
                  |  |                 |     +--:(boundary)
                  |  |                 |        +--rw latency-boundary?     uint16
                  |  |                 +--rw jitter
                  |  |                 |  +--rw (flavor)?
                  |  |                 |     +--:(lowest)
                  |  |                 |     |  +--rw use-lowest-jitter?   empty
                  |  |                 |     +--:(boundary)
                  |  |                 |        +--rw latency-boundary?    uint32
                  |  |                 +--rw bandwidth
                  |  |                    +--rw guaranteed-bw-percent    uint8
                  |  |                    +--rw end-to-end?              empty
                  |  +--rw carrierscarrier {carrierscarrier}?
                  |  |  +--rw signalling-type?   enumeration
                  |  +--rw multicast {multicast}?
                  |     +--rw multicast-site-type?        enumeration
                  |     +--rw multicast-address-family
                  |     |  +--rw ipv4?   boolean {ipv4}?
                  |     |  +--rw ipv6?   boolean {ipv6}?
                  |     +--rw protocol-type?              enumeration
                  +--rw routing-protocols
                  |  +--rw routing-protocol* [type]
                  |     +--rw type      identityref
                  |     +--rw ospf {rtg-ospf}?
                  |     |  +--rw address-family*   address-family
                  |     |  +--rw area-address      yang:dotted-quad
                  |     |  +--rw metric?           uint16
                  |     |  +--rw sham-links {rtg-ospf-sham-link}?
                  |     |     +--rw sham-link* [target-site]
                  |     |        +--rw target-site    svc-id
                  |     |        +--rw metric?        uint16
                  |     +--rw bgp {rtg-bgp}?
                  |     |  +--rw autonomous-system    uint32
                  |     |  +--rw address-family*      address-family
                  |     +--rw static
                  |     |  +--rw cascaded-lan-prefixes
                  |     |     +--rw ipv4-lan-prefixes* [lan next-hop] {ipv4}?
                  |     |     |  +--rw lan         inet:ipv4-prefix
                  |     |     |  +--rw lan-tag?    string
                  |     |     |  +--rw next-hop    inet:ipv4-address
                  |     |     +--rw ipv6-lan-prefixes* [lan next-hop] {ipv6}?
                  |     |        +--rw lan         inet:ipv6-prefix
                  |     |        +--rw lan-tag?    string
                  |     |        +--rw next-hop    inet:ipv6-address
                  |     +--rw rip {rtg-rip}?
                  |     |  +--rw address-family*   address-family
                  |     +--rw vrrp {rtg-vrrp}?
                  |        +--rw address-family*   address-family
                  +--rw availability
                  |  +--rw access-priority?   uint32
                  +--rw vpn-attachment
                     +--rw (attachment-flavor)
                        +--:(vpn-policy-id)
                        |  +--rw vpn-policy-id?   -> ../../../../vpn-policies/vpn-policy/vpn-policy-id
                        +--:(vpn-id)
                           +--rw vpn-id?          -> /l3vpn-svc/vpn-services/vpn-service/vpn-id
                           +--rw site-role?       identityref
          ]]>
        </artwork>
      </figure>

      <section anchor="features" title="Features and Augmentation">

         <t>The model defined in this document implements many features that
            allow implementations to be modular.  As an example, an
            implementation may support only IPv4 VPNs (IPv4 feature), IPv6 VPNs
            (IPv6 feature), or both (by advertising both features).  The routing
            protocols proposed to the customer may also be enabled through
            features.  This model also defines some features for options that
            are more advanced, such as support for extranet VPNs (<xref target="extranet" />),
            site diversity (<xref target="deciding" />), and QoS (<xref target="qos" />).</t>

         <t>In addition, as for any YANG model, this service model can be
            augmented to implement new behaviors or specific features.  For
            example, this model uses different options for IP address
            assignments; if those options do not fulfill all requirements, new
            options can be added through augmentation.</t>

      </section>

      <section anchor="overview" title="VPN Service Overview">

        <t>A vpn-service list item contains generic information about the VPN
           service.  The "vpn-id" provided in the vpn-service list refers to an
           internal reference for this VPN service, while the customer name
           refers to a more-explicit reference to the customer.  This identifier
           is purely internal to the organization responsible for the VPN
           service.</t>

      <section anchor="vpntopo" title="VPN Service Topology">

         <t>The type of VPN service topology is required for configuration.  Our
            proposed model supports any-to-any, Hub and Spoke (where Hubs can
            exchange traffic), and "Hub and Spoke disjoint" (where Hubs cannot
            exchange traffic).  New topologies could be added via augmentation.
            By default, the any-to-any VPN service topology is used.</t>

         <section anchor="rt" title="Route Target Allocation">

            <t>A Layer 3 PE-based VPN is built using route targets (RTs) as
               described in <xref target="RFC4364" />.  The management system is 
			   expected to automatically allocate a set of RTs upon receiving a 
			   VPN service creation request.  How the management system allocates 
			   RTs is out of scope for this document, but multiple ways could be 
			   envisaged, as described below.</t>

            <figure>
              <artwork align="center">
                <![CDATA[
                                 Management system
                  <------------------------------------------------->
                                              Request RT
                   +-----------------------+  Topo a2a   +----------+
        RESTCONF   |                       |  ----->     |          |
User ------------- | Service Orchestration |             | Network  |
        l3vpn-svc  |                       |  <-----     |   OSS    |
          Model    +-----------------------+   Response  +----------+
                                               RT1, RT2
                ]]>
              </artwork>
            </figure>

            <t>In the example above, a service orchestration, owning the
               instantiation of this service model, requests RTs to the network OSS.
               Based on the requested VPN service topology, the network OSS replies
               with one or multiple RTs.  The interface between this service
               orchestration and the network OSS is out of scope for this document.</t>

            <figure>
              <artwork align="center">
                <![CDATA[
                   +---------------------------+
        RESTCONF   |                           |
User ------------- |   Service Orchestration   |
        l3vpn-svc  |                           |
          Model    |                           |
                   |  RT pool: 10:1->10:10000  |
                   |  RT pool: 20:50->20:5000  |
                   +---------------------------+
                ]]>
              </artwork>
            </figure>

            <t>In the example above, a service orchestration, owning the
               instantiation of this service model, owns one or more pools of RTs
               (specified by the SP) that can be allocated.  Based on the requested
               VPN service topology, it will allocate one or multiple RTs from the
               pool.</t>

            <t>The mechanisms shown above are just examples and should not be
               considered an exhaustive list of solutions.</t>

         </section>

         <section anchor="any2any" title="Any-to-Any">

            <figure>
              <artwork align="center">
                <![CDATA[
+------------------------------------------------------------+
|  VPN1_Site1 ------ PE1               PE2 ------ VPN1_Site2 |
|                                                            |
|  VPN1_Site3 ------ PE3               PE4 ------ VPN1_Site4 |
+------------------------------------------------------------+

                Any-to-Any VPN Service Topology
                ]]>
              </artwork>
            </figure>

            <t>In the any-to-any VPN service topology, all VPN sites can communicate
               with each other without any restrictions.  The management system that
               receives an any-to-any IP VPN service request through this model is
               expected to assign and then configure the VRF and RTs on the
               appropriate PEs.  In the any-to-any case, a single RT is generally
               required, and every VRF imports and exports this RT.</t>

         </section>

         <section anchor="hubnspoke" title="Hub and Spoke">

            <figure>
              <artwork align="center">
                <![CDATA[
+-------------------------------------------------------------+
|   Hub_Site1 ------ PE1               PE2 ------ Spoke_Site1 |
|                          +----------------------------------+
|                          |
|                          +----------------------------------+
|   Hub_Site2 ------ PE3               PE4 ------ Spoke_Site2 |
+-------------------------------------------------------------+

                Hub-and-Spoke VPN Service Topology
                ]]>
              </artwork>
            </figure>

            <t>In the Hub-and-Spoke VPN service topology, all Spoke sites can
               communicate only with Hub sites but not with each other, and Hubs can
               also communicate with each other.  The management system that owns an
               any-to-any IP VPN service request through this model is expected to
               assign and then configure the VRF and RTs on the appropriate PEs.  In
               the Hub-and-Spoke case, two RTs are generally required (one RT for
               Hub routes and one RT for Spoke routes).  A Hub VRF that connects Hub
               sites will export Hub routes with the Hub RT and will import Spoke
               routes through the Spoke RT.  It will also import the Hub RT to allow
               Hub-to-Hub communication.  A Spoke VRF that connects Spoke sites will
               export Spoke routes with the Spoke RT and will import Hub routes
               through the Hub RT.</t>

            <t>The management system MUST take into account constraints on Hub-and-
               Spoke connections.  For example, if a management system decides to
               mesh a Spoke site and a Hub site on the same PE, it needs to mesh
               connections in different VRFs, as shown in the figure below.</t>

            <figure>
              <artwork align="center">
                <![CDATA[
   Hub_Site ------- (VRF_Hub)  PE1
                              (VRF_Spoke)
                                /  |
Spoke_Site1 -------------------+   |
                                   |
Spoke_Site2 -----------------------+
                ]]>
              </artwork>
            </figure>

         </section>

         <section anchor="hubnspokedj" title="Hub and Spoke Disjoint">

              <figure>
                <artwork align="center">
                  <![CDATA[
+-------------------------------------------------------------+
|   Hub_Site1 ------ PE1               PE2 ------ Spoke_Site1 |
+--------------------------+  +-------------------------------+
                           |  |
+--------------------------+  +-------------------------------+
|   Hub_Site2 ------ PE3               PE4 ------ Spoke_Site2 |
+-------------------------------------------------------------+

          Hub and Spoke Disjoint VPN Service Topology
                  ]]>
                </artwork>
              </figure>

              <t>In the Hub and Spoke disjoint VPN service topology, all Spoke sites
                 can communicate only with Hub sites but not with each other, and Hubs
                 cannot communicate with each other.  The management system that owns
                 an any-to-any IP VPN service request through this model is expected
                 to assign and then configure the VRF and RTs on the appropriate PEs.
                 In the Hub-and-Spoke case, two RTs are required (one RT for Hub
                 routes and one RT for Spoke routes).  A Hub VRF that connects Hub
                 sites will export Hub routes with the Hub RT and will import Spoke
                 routes through the Spoke RT.  A Spoke VRF that connects Spoke sites
                 will export Spoke routes with the Spoke RT and will import Hub routes
                 through the Hub RT.</t>

              <t>The management system MUST take into account constraints on Hub-and-
                 Spoke connections, as in the previous case.</t>

              <t>Hub and Spoke disjoint can also be seen as multiple Hub-and-Spoke
                 VPNs (one per Hub) that share a common set of Spoke sites.</t>

           </section>

        </section>

        <section anchor="cloud" title="Cloud Access">

           <t>The proposed model provides cloud access configuration via the
              "cloud-accesses" container.  The usage of cloud-access is targeted
              for the public cloud.  An Internet access can also be considered a
              public cloud access service.  The cloud-accesses container provides
              parameters for network address translation and authorization rules.</t>

           <t>A private cloud access may be addressed through NNIs, as described in
              <xref target="defnnis" />.</t>

           <t>A cloud identifier is used to reference the target service.  This
              identifier is local to each administration.</t>

           <t>The model allows for source address translation before accessing the
              cloud.  IPv4-to-IPv4 address translation (NAT44) is the only
              supported option, but other options can be added through
              augmentation.  If IP source address translation is required to access
              the cloud, the "enabled" leaf MUST be set to true in the "nat44"
              container.  An IP address may be provided in the "customer-address"
              leaf if the customer is providing the IP address to be used for the
              cloud access.  If the SP is providing this address,
              "customer-address" is not necessary, as it can be picked from a pool
              of SPs.</t>

           <t>By default, all sites in the IP VPN MUST be authorized to access the
              cloud.  If restrictions are required, a user MAY configure the
              "permit-site" or "deny-site" leaf-list.  The permit-site leaf-list
              defines the list of sites authorized for cloud access.  The deny-site
              leaf-list defines the list of sites denied for cloud access.  The
              model supports both "deny-any-except" and "permit-any-except"
              authorization.</t>

           <t>How the restrictions will be configured on network elements is out of
              scope for this document.</t>

              <figure>
                <artwork align="center">
                  <![CDATA[
          IP VPN
++++++++++++++++++++++++++++++++     ++++++++++++
+             Site 3           + --- +  Cloud 1 +
+ Site 1                       +     ++++++++++++
+                              +
+ Site 2                       + --- ++++++++++++
+                              +     + Internet +
+            Site 4            +     ++++++++++++
++++++++++++++++++++++++++++++++
             |
        +++++++++++
        + Cloud 2 +
        +++++++++++
                  ]]>
                </artwork>
              </figure>

              <t>In the example above, we configure the global VPN to access the
                 Internet by creating a cloud-access pointing to the cloud identifier
                 for the Internet service.  No authorized sites will be configured, as
                 all sites are required to access the Internet.  The
                 "address-translation/nat44/enabled" leaf will be set to true.</t>

              <figure>
                <artwork align="center">
                  <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>123456487</vpn-id>
      <cloud-accesses>
        <cloud-access>
          <cloud-identifier>INTERNET</cloud-identifier>
          <address-translation>
            <nat44>
              <enabled>true</enabled>
            </nat44>
          </address-translation>
        </cloud-access>
      </cloud-accesses>
    </vpn-service>
  </vpn-services>
</l3vpn-svc>
                  ]]>
                </artwork>
              </figure>

              <t>If Site 1 and Site 2 require access to Cloud 1, a new cloud-access
                 pointing to the cloud identifier of Cloud 1 will be created.  The
                 permit-site leaf-list will be filled with a reference to Site 1 and
                 Site 2.</t>

              <figure>
                <artwork align="center">
                  <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>123456487</vpn-id>
      <cloud-accesses>
        <cloud-access>
          <cloud-identifier>Cloud1</cloud-identifier>
          <permit-site>site1</permit-site>
          <permit-site>site2</permit-site>
        </cloud-access>
      </cloud-accesses>
    </vpn-service>
  </vpn-services>
</l3vpn-svc>
                  ]]>
                </artwork>
              </figure>

              <t>If all sites except Site 1 require access to Cloud 2, a new
                 cloud-access pointing to the cloud identifier of Cloud 2 will be
                 created.  The deny-site leaf-list will be filled with a reference to
                 Site 1.</t>

              <figure>
                <artwork align="center">
                  <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>123456487</vpn-id>
      <cloud-accesses>
        <cloud-access>
          <cloud-identifier>Cloud2</cloud-identifier>
          <deny-site>site1</deny-site>
        </cloud-access>
      </cloud-accesses>
    </vpn-service>
  </vpn-services>
</l3vpn-svc>
                  ]]>
                </artwork>
              </figure>
	  		  		  
              <t>A service with more than one cloud access is functionally
                 identical to multiple services each with a single cloud access, 
				 where the sites that belong to each service in the latter case 
				 correspond with the authorized sites for each cloud access in the
				 former case. However, defining a single service with multiple cloud
				 accesses may be operationally simpler.</t>
				 
           </section>

           <section anchor="multisvc" title="Multicast Service">

              <t>Multicast in IP VPNs is described in <xref target="RFC6513" />.</t>

              <t>If multicast support is required for an IP VPN, some global multicast
                 parameters are required as input for the service request.</t>

              <t>Users of this model will need to provide the flavors of trees that
                 will be used by customers within the IP VPN (customer tree).  The
                 proposed model supports bidirectional, shared, and source-based trees
                 (and can be augmented).  Multiple flavors of trees can be supported
                 simultaneously.</t>

              <figure>
                <artwork align="center">
                  <![CDATA[
                               Operator network
                               ______________
                              /               \
                             |                 |
                      (SSM tree)               |
Recv (IGMPv3) -- Site2 ------- PE2             |
                             |             PE1 --- Site1 --- Source1
                             |                 |        \
                             |                 |         -- Source2
                             |                 |
                       (ASM tree)              |
Recv (IGMPv2) -- Site3 ------- PE3             |
                             |                 |
                       (SSM tree)              |
Recv (IGMPv3) -- Site4 ------- PE4             |
                             | /               |
Recv (IGMPv2) -- Site5 --------                |
                       (ASM tree)              |
                             |                 |
                              \_______________/
                   ]]>
                 </artwork>
               </figure>

               <t>When an ASM flavor is requested, this model requires that the "rp"
                  and "rp-discovery" parameters be filled.  Multiple RP-to-group
                  mappings can be created using the "rp-group-mappings" container. For
                  each mapping, the SP can manage the RP service by setting the
                  "provider-managed/enabled" leaf to true.  In the case of a provider-
                  managed RP, the user can request RP redundancy and/or optimal traffic
                  delivery.  Those parameters will help the SP select the appropriate
                  technology or architecture to fulfill the customer service
                  requirement: for instance, in the case of a request for optimal
                  traffic delivery, an SP may use Anycast-RP or RP-tree-to-SPT
                  switchover architectures.</t>

               <t>In the case of a customer-managed RP, the RP address must be filled
                  in the RP-to-group mappings using the "rp-address" leaf.  This leaf
                  is not needed for a provider-managed RP.</t>

               <t>Users can define a specific mechanism for RP discovery, such as the
                  "auto-rp", "static-rp", or "bsr-rp" modes.  By default, the model
                  uses "static-rp" if ASM is requested.  A single rp-discovery
                  mechanism is allowed for the VPN.  The "rp-discovery" container can
                  be used for both provider-managed and customer-managed RPs.  In the
                  case of a provider-managed RP, if the user wants to use "bsr-rp" as a
                  discovery protocol, an SP should consider the provider-managed
                  "rp-group-mappings" for the "bsr-rp" configuration.  The SP will then
                  configure its selected RPs to be "bsr-rp-candidates".  In the case of
                  a customer-managed RP and a "bsr-rp" discovery mechanism, the
                  "rp-address" provided will be the bsr-rp candidate.</t>

            </section>

            <section anchor="extranet" title="Extranet VPNs">

               <t>There are some cases where a particular VPN needs access to resources
                  (servers, hosts, etc.) that are external.  Those resources may be
                  located in another VPN.</t>

               <figure>
                 <artwork align="center">
                   <![CDATA[
            +-----------+           +-----------+
           /             \         /             \
Site A -- |    VPN A      |  ---  |    VPN B      | --- Site B
           \             /         \             / (Shared
            +-----------+           +-----------+   resources)
                   ]]>
                 </artwork>
               </figure>

               <t>In the figure above, VPN B has some resources on Site B that need to
                  be available to some customers/partners.  VPN A must be able to
                  access those VPN B resources.</t>

               <t>Such a VPN connection scenario can be achieved via a VPN policy as
                  defined in <xref target="vpnpolicy" />.  But there are some simple 
				  cases where a particular VPN (VPN A) needs access to all resources 
				  in another VPN (VPN B).  The model provides an easy way to set up 
				  this connection using the "extranet-vpns" container.</t>

               <t>The extranet-vpns container defines a list of VPNs a particular VPN
                  wants to access.  The extranet-vpns container must be used on
                  customer VPNs accessing extranet resources in another VPN.  In the
                  figure above, in order to provide VPN A with access to VPN B, the
                  extranet-vpns container needs to be configured under VPN A with an
                  entry corresponding to VPN B.  There is no service configuration
                  requirement on VPN B.</t>

               <t>Readers should note that even if there is no configuration
                  requirement on VPN B, if VPN A lists VPN B as an extranet, all sites
                  in VPN B will gain access to all sites in VPN A.</t>

               <t>The "site-role" leaf defines the role of the local VPN sites in the
                  target extranet VPN service topology.  Site roles are defined in
                  <xref target="siterole" />.  Based on this, the requirements described
				  in <xref target="siterole" /> regarding the site-role leaf are also 
				  applicable here.</t>

               <t>In the example below, VPN A accesses VPN B resources through an
                  extranet connection.  A Spoke role is required for VPN A sites, as
                  sites from VPN A must not be able to communicate with each other
                  through the extranet VPN connection.</t>

               <figure>
                 <artwork align="center">
                   <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNB</vpn-id>
      <vpn-service-topology>hub-spoke</vpn-service-topology>
    </vpn-service>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
      <vpn-service-topology>any-to-any</vpn-service-topology>
      <extranet-vpns>
        <extranet-vpn>
          <vpn-id>VPNB</vpn-id>
          <local-sites-role>spoke-role</local-sites-role>
        </extranet-vpn>
      </extranet-vpns>
    </vpn-service>
  </vpn-services>
</l3vpn-svc>
                   ]]>
                 </artwork>
               </figure>

               <t>This model does not define how the extranet configuration will be
                  achieved.</t>

               <t>Any VPN interconnection scenario that is more complex (e.g., only
                  certain parts of sites on VPN A accessing only certain parts of sites
                  on VPN B) needs to be achieved using a VPN attachment as defined in
                  <xref target="attachvpn" />, and especially a VPN policy as defined in
                  <xref target="vpnpolicy" />.</t>

            </section>

         </section>

         <section anchor="site" title="Site Overview">

            <t>A site represents a connection of a customer office to one or more
               VPN services. Each site is associated with one or more location.
			   </t>

            <figure>
              <artwork align="center">
                <![CDATA[
                                               +-------------+
                                              /               \
+------------------+                   +-----|      VPN1       |
|                  |                   |      \               /
|  New York Office |------ (site) -----+       +-------------+
|                  |                   |       +-------------+
+------------------+                   |      /               \
                                       +-----|      VPN2       |
                                              \               /
                                               +-------------+
                ]]>
              </artwork>
            </figure>

            <t>A site has several characteristics:

               <list style="symbols">
                  <t>Unique identifier (site-id): uniquely identifies the site within
                     the overall network infrastructure.  The identifier is a string
                     that allows any encoding for the local administration of the VPN
                     service.</t>

                  <t>Locations (locations): site location information that allows easy
                     retrieval of information from the nearest available resources.  A
                     site may be composed of multiple locations. Alternatively,two or 
					 more sites can be associated with the same location, by referencing
					 the same location ID.</t>

                  <t>Devices (devices): allows the customer to request one or more
                     customer premises equipment entities from the SP for a particular
                     site.</t>

                  <t>Management (management): defines the type of management for the
                     site -- for example, co-managed, customer-managed, or provider-
                     managed.  See <xref target="manage" />.</t>

                  <t>Site network accesses (site-network-accesses): defines the list of
                     network accesses associated with the sites, and their properties
                     -- especially bearer, connection, and service parameters.</t>
               </list></t>

            <t>A site-network-access represents an IP logical connection of a site.
               A site may have multiple site-network-accesses.</t>

            <figure>
              <artwork align="center">
                <![CDATA[
+------------------+             Site
|                  |-----------------------------------
|                  |****** (site-network-access#1) ******
|  New York Office |
|                  |****** (site-network-access#2) ******
|                  |-----------------------------------
+------------------+
                ]]>
              </artwork>
            </figure>

            <t>Multiple site-network-accesses are used, for instance, in the case of
               multihoming.  Some other meshing cases may also include multiple
               site-network-accesses.</t>

            <t>The site configuration is viewed as a global entity; we assume that
               it is mostly the management system&apos;s role to split the parameters
               between the different elements within the network.  For example, in
               the case of the site-network-access configuration, the management
               system needs to split the overall parameters between the PE
               configuration and the CE configuration.</t>

            <section anchor="devnloc" title="Devices and Locations">

               <t>A site may be composed of multiple locations.  All the locations will
                  need to be configured as part of the "locations" container and list.
                  A typical example of a multi-location site is a headquarters office
                  in a city composed of multiple buildings.  Those buildings may be
                  located in different parts of the city and may be linked by
                  intra-city fibers (customer metropolitan area network).  In such a
                  case, when connecting to a VPN service, the customer may ask for
                  multihoming based on its distributed locations.</t>

               <figure>
                 <artwork align="center">
                   <![CDATA[
  New York Site

+------------------+             Site
| +--------------+ |-----------------------------------
| | Manhattan    | |****** (site-network-access#1) ******
| +--------------+ |
| +--------------+ |
| | Brooklyn     | |****** (site-network-access#2) ******
| +--------------+ |
|                  |-----------------------------------
+------------------+
                   ]]>
                 </artwork>
               </figure>

               <t>A customer may also request some premises equipment entities (CEs)
                  from the SP via the "devices" container.  Requesting a CE implies a
                  provider-managed or co-managed model.  A particular device must be
                  ordered to a particular already-configured location.  This would help
                  the SP send the device to the appropriate postal address.  In a
                  multi-location site, a customer may, for example, request a CE for
                  each location on the site where multihoming must be implemented.  In
                  the figure above, one device may be requested for the Manhattan
                  location and one other for the Brooklyn location.</t>

               <t>By using devices and locations, the user can influence the
                  multihoming scenario he wants to implement: single CE, dual CE, etc.</t>

            </section>

            <section anchor="sitenetacc" title="Site Network Accesses">

               <t>As mentioned earlier, a site may be multihomed.  Each IP network
                  access for a site is defined in the "site-network-accesses"
                  container.  The site-network-access parameter defines how the site is
                  connected on the network and is split into three main classes of
                  parameters:

                  <list style="symbols">

                     <t>bearer: defines requirements of the attachment (below Layer 3).</t>

                     <t>connection: defines Layer 3 protocol parameters of the attachment.</t>

                     <t>availability: defines the site&apos;s availability policy.  The
                        availability parameters are defined in <xref target="availability" />.</t>

                  </list></t>

               <t>The site-network-access has a specific type
                  (site-network-access-type).  This document defines two types:

                  <list style="symbols">

                     <t>point-to-point: describes a point-to-point connection between the
                        SP and the customer.</t>

                     <t>multipoint: describes a multipoint connection between the SP and
                        the customer.</t>

                  </list></t>

                  <t>The type of site-network-access may have an impact on the parameters
                     offered to the customer, e.g., an SP may not offer encryption for
                     multipoint accesses.  It is up to the provider to decide what
                     parameter is supported for point-to-point and/or multipoint accesses;
                     this topic is out of scope for this document.  Some containers
                     proposed in the model may require extensions in order to work
                     properly for multipoint accesses.</t>

                  <section anchor="bearer" title="Bearer">

                     <t>The bearer container defines the requirements for the site attachment
                        to the provider network that are below Layer 3.</t>

                     <t>The bearer parameters will help determine the access media to be
                        used.  This is further described in <xref target="accesstype" />.</t>

                  </section>

                  <section anchor="connection" title="Connection">

                     <t>The "ip-connection" container defines the protocol parameters of the
                        attachment (IPv4 and IPv6).  Depending on the management mode, it
                        refers to PE-CE addressing or CE-to-customer-LAN addressing.  In any
                        case, it describes the responsibility boundary between the provider
                        and the customer.  For a customer-managed site, it refers to the
                        PE-CE connection.  For a provider-managed site, it refers to the
                        CE-to-LAN connection.</t>

                     <section anchor="ipaddr" title="IP Addressing">

                        <t>An IP subnet can be configured for either IPv4 or IPv6 Layer 3
                           protocols.  For a dual-stack connection, two subnets will be
                           provided, one for each address family.</t>

                        <t>The "address-allocation-type" determines how the address allocation
                           needs to be done.  The current model defines five ways to perform IP
                           address allocation:

                           <list style="symbols">

                              <t>provider-dhcp: The provider will provide DHCP service for customer
                                 equipment; this is applicable to either the "IPv4" container or
                                 the "IPv6" container.</t>

                              <t>provider-dhcp-relay: The provider will provide DHCP relay service
                                 for customer equipment; this is applicable to both IPv4 and IPv6
                                 addressing.  The customer needs to populate the DHCP server list
                                 to be used.</t>

                              <t>static-address: Addresses will be assigned manually; this is
                                 applicable to both IPv4 and IPv6 addressing.</t>

                              <t>slaac: This parameter enables stateless address autoconfiguration
                                 <xref target="RFC4862" />.  This is applicable to IPv6 only.</t>

                              <t>provider-dhcp-slaac: The provider will provide DHCP service for
                                 customer equipment, as well as stateless address
                                 autoconfiguration.  This is applicable to IPv6 only.</t>

                           </list></t>

                        <t>In the dynamic addressing mechanism, the SP is expected to provide at
                           least the IP address, mask, and default gateway information.In the 
						   case of multiple site-network-access points belonging to the same 
						   VPN, address space allocated for one site-network-access should not 
						   conflict with one allocated for other site-network-accesses.</t>

                     </section>

                     <section anchor="oam" title="OAM">

                        <t>A customer may require a specific IP connectivity fault detection
                           mechanism on the IP connection.  The model supports BFD as a fault
                           detection mechanism.  This can be extended with other mechanisms via
                           augmentation.  The provider can propose some profiles to the
                           customer, depending on the service level the customer wants to
                           achieve.  Profile names must be communicated to the customer.  This
                           communication is out of scope for this document.  Some fixed values
                           for the holdtime period may also be imposed by the customer if the
                           provider allows the customer this function.</t>

                        <t>The "oam" container can easily be augmented by other mechanisms; in
                           particular, work done by the LIME Working Group
                           (https://datatracker.ietf.org/wg/lime/charter/) may be reused in
                           applicable scenarios.</t>

                     </section>

                  </section>

                  <section anchor="inherit" title="Inheritance of Parameters Defined at Site Level and Site Network Access Level">

                     <t>Some parameters can be configured at both the site level and the
                        site-network-access level, e.g., routing, services, security.
                        Inheritance applies when parameters are defined at the site level.
                        If a parameter is configured at both the site level and the access
                        level, the access-level parameter MUST override the site-level
                        parameter.  Those parameters will be described later in this
                        document.</t>

                     <t>In terms of provisioning impact, it will be up to the implementation
                        to decide on the appropriate behavior when modifying existing
                        configurations.  But the SP will need to communicate to the user
                        about the impact of using inheritance.  For example, if we consider
                        that a site has already provisioned three site-network-accesses, what
                        will happen if a customer changes a service parameter at the site
                        level?  An implementation of this model may update the service
                        parameters of all already-provisioned site-network-accesses (with
                        potential impact on live traffic), or it may take into account this
                        new parameter only for the new sites.</t>

                  </section>

               </section>

               </section>

               <section anchor="siterole" title="Site Role">

                  <t>A VPN has a particular service topology, as described in
                     <xref target="vpntopo" />.  As a consequence, each site belonging to a VPN is
                     assigned with a particular role in this topology.  The site-role leaf
                     defines the role of the site in a particular VPN topology.</t>

                  <t>In the any-to-any VPN service topology, all sites MUST have the same
                     role, which will be "any-to-any-role".</t>

                  <t>In the Hub-and-Spoke VPN service topology or the Hub and Spoke
                     disjoint VPN service topology, sites MUST have a Hub role or a
                     Spoke role.</t>

               </section>

               <section anchor="sitemultivpn" title="Site Belonging to Multiple VPNs">

                  <section anchor="sitevpnflav" title="Site VPN Flavor">

                     <t>A site may be part of one or multiple VPNs.  The "site-vpn-flavor"
                        defines the way the VPN multiplexing is done.  The current version of
                        the model supports four flavors:

                        <list style="symbols">

                           <t>site-vpn-flavor-single: The site belongs to only one VPN.</t>

                           <t>site-vpn-flavor-multi: The site belongs to multiple VPNs, and all
                              the logical accesses of the sites belong to the same set of VPNs.</t>

                           <t>site-vpn-flavor-sub: The site belongs to multiple VPNs with
                              multiple logical accesses.  Each logical access may map to
                              different VPNs (one or many).</t>

                           <t>site-vpn-flavor-nni: The site represents an option A NNI.</t>

                        </list></t>

                     <section anchor="singlevpn" title="Single VPN Attachment: site-vpn-flavor-single">

                        <t>The figure below describes a single VPN attachment.  The site
                           connects to only one VPN.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
                                                   +--------+
+------------------+             Site             /          \
|                  |-----------------------------|            |
|                  |***(site-network-access#1)***|    VPN1    |
|  New York Office |                             |            |
|                  |***(site-network-access#2)***|            |
|                  |-----------------------------|            |
+------------------+                              \          /
                                                   +--------+
                            ]]>
                          </artwork>
                        </figure>

                     </section>

                     <section anchor="multivpn" title="MultiVPN Attachment: site-vpn-flavor-multi">

                        <t>The figure below describes a site connected to multiple VPNs.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
                                                        +---------+
                                                   +---/----+      \
+------------------+             Site             /   |      \      |
|                  |--------------------------------- |       |VPN B|
|                  |***(site-network-access#1)******* |       |     |
|  New York Office |                             |    |       |     |
|                  |***(site-network-access#2)*******  \      |    /
|                  |-----------------------------| VPN A+-----|---+
+------------------+                              \          /
                                                   +--------+
                            ]]>
                          </artwork>
                        </figure>

                        <t>In the example above, the New York office is multihomed.  Both
                           logical accesses are using the same VPN attachment rules, and both
                           are connected to VPN A and VPN B.</t>

                        <t>Reaching VPN A or VPN B from the New York office will be done via
                           destination-based routing.  Having the same destination reachable
                           from the two VPNs may cause routing troubles.  The customer
                           administration&apos;s role in this case would be to ensure the appropriate
                           mapping of its prefixes in each VPN.</t>

                     </section>

                     <section anchor="subvpn" title="SubVPN Attachment: site-vpn-flavor-sub">

                        <t>The figure below describes a subVPN attachment.  The site connects to
                           multiple VPNs, but each logical access is attached to a particular
                           set of VPNs.  A typical use case for a subVPN is a customer site used
                           by multiple affiliates with private resources for each affiliate that
                           cannot be shared (communication between the affiliates is prevented).
                           It is similar to have separate sites, but in the case of a SubVPN, the 
                           customer can share some physical components at a single location, while
                           maintaining strong communication isolation between the affiliates.
						   In this example, site-network-access#1 is attached to VPN B, while
                           site-network-access#2 is attached to VPN A.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
+------------------+         Site                      +--------+
|                  |----------------------------------/          \
|                  |****(site-network-access#1)******|    VPN B   |
|  New York Office |                                  \          /
|                  |                                   +--------+
|                  |                                   +--------+
|                  |                                  /          \
|                  |****(site-network-access#2)******|    VPN A   |
|                  |                                  \          /
|                  |                                   +--------+
|                  |-----------------------------------
+------------------+
                            ]]>
                          </artwork>
                        </figure>

                        <t>A multiVPN can be implemented in addition to a subVPN; as a
                           consequence, each site-network-access can access multiple VPNs.  In
                           the example below, site-network-access#1 is mapped to VPN B and
                           VPN C, while site-network-access#2 is mapped to VPN A and VPN D.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
+-----------------+         Site                    +------+
|                 |--------------------------------/       +-----+
|                 |****(site-network-access#1)****| VPN B /       \
| New York Office |                                \     |  VPN C  |
|                 |                                 +-----\       /
|                 |                                        +-----+
|                 |
|                 |                                 +-------+
|                 |                                /        +-----+
|                 |****(site-network-access#2)****| VPN A  /       \
|                 |                                \      | VPN D   |
|                 |                                 +------\       /
|                 |---------------------------------        +-----+
+-----------------+
                            ]]>
                          </artwork>
                        </figure>

                        <t>Multihoming is also possible with subVPNs; in this case,
                           site-network-accesses are grouped, and a particular group will have
                           access to the same set of VPNs.  In the example below,
                           site-network-access#1 and site-network-access#2 are part of the same
                           group (multihomed together) and are mapped to VPN B and VPN C; in
                           addition, site-network-access#3 and site-network-access#4 are part of
                           the same group (multihomed together) and are mapped to VPN A and
                           VPN D.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
+-----------------+         Site                     +------+
|                 |---------------------------------/       +-----+
|                 |****(site-network-access#1)*****| VPN B /       \
| New York Office |****(site-network-access#2)***** \     |  VPN C  |
|                 |                                  +-----\       /
|                 |                                         +-----+
|                 |
|                 |                                  +------+
|                 |                                 /       +-----+
|                 |****(site-network-access#3)*****| VPN A /       \
|                 |****(site-network-access#4)***** \     | VPN D   |
|                 |                                  +-----\       /
|                 |----------------------------------       +-----+
+-----------------+
                            ]]>
                          </artwork>
                        </figure>

                        <t>In terms of service configuration, a subVPN can be achieved by
                           requesting that the site-network-access use the same bearer (see
                           <xref target="accessdiversity" /> for more details).</t>

                     </section>

                     <section anchor="nni" title="NNI: site-vpn-flavor-nni">

                        <t>A Network-to-Network Interface (NNI) scenario may be modeled using
                           the sites container (see <xref target="opta" />).  Using the sites
						   container to model an NNI is only one possible option for NNIs (see
                           <xref target="defnnis" />).  This option is called "option A" by 
						   reference to the option A NNI defined in <xref target="RFC4364" />.  
						   It is helpful for the SP to indicate that the requested VPN connection 
						   is not a regular site but rather is an NNI, as specific default device
						   configuration parameters may be applied in the case of NNIs (e.g., 
						   ACLs, routing policies).</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
       SP A                                             SP B
  -------------------                         -------------------
 /                   \                       /                   \
|                     |                     |                     |
|                 ++++++++ Inter-AS link ++++++++                 |
|                 +      +_______________+      +                 |
|                 +  (VRF1)---(VPN1)----(VRF1)  +                 |
|                 + ASBR +               + ASBR +                 |
|                 +  (VRF2)---(VPN2)----(VRF2)  +                 |
|                 +      +_______________+      +                 |
|                 ++++++++               ++++++++                 |
|                     |                     |                     |
|                     |                     |                     |
|                     |                     |                     |
|                 ++++++++ Inter-AS link ++++++++                 |
|                 +      +_______________+      +                 |
|                 +  (VRF1)---(VPN1)----(VRF1)  +                 |
|                 + ASBR +               + ASBR +                 |
|                 +  (VRF2)---(VPN2)----(VRF2)  +                 |
|                 +      +_______________+      +                 |
|                 ++++++++               ++++++++                 |
|                     |                     |                     |
|                     |                     |                     |
 \                   /                       \                   /
  -------------------                         -------------------
                            ]]>
                          </artwork>
                        </figure>

                        <t>The figure above describes an option A NNI scenario that can be
                           modeled using the sites container.  In order to connect its customer
                           VPNs (VPN1 and VPN2) in SP B, SP A may request the creation of some
                           site-network-accesses to SP B.  The site-vpn-flavor-nni will be used
                           to inform SP B that this is an NNI and not a regular customer site.
                           The site-vpn-flavor-nni may be multihomed and multiVPN as well.</t>

                     </section>

                  </section>

                  <section anchor="attachvpn" title="Attaching a Site to a VPN">

                     <t>Due to the multiple site-vpn flavors, the attachment of a site to an
                        IP VPN is done at the site-network-access (logical access) level
                        through the "vpn-attachment" container.  The vpn-attachment container
                        is mandatory.  The model provides two ways to attach a site to a VPN:

                        <list style="symbols">

                           <t>By referencing the target VPN directly.</t>

                           <t>By referencing a VPN policy for attachments that are more complex.</t>

                        </list></t>

                     <t>A choice is implemented to allow the user to choose the flavor that
                        provides the best fit.</t>

                     <section anchor="refvpn" title="Referencing a VPN">

                        <t>Referencing a vpn-id provides an easy way to attach a particular
                           logical access to a VPN.  This is the best way in the case of a
                           single VPN attachment or subVPN with a single VPN attachment per
                           logical access.  When referencing a vpn-id, the site-role setting
                           must be added to express the role of the site in the target VPN
                           service topology.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
    </vpn-service>
    <vpn-service>
      <vpn-id>VPNB</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <management>
        <type>customer-managed</type>
      </management>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>LA1</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
        <site-network-access>
          <site-network-access-id>LA2</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <vpn-attachment>
            <vpn-id>VPNB</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
  </sites>
</l3vpn-svc>

                            ]]>
                          </artwork>
                        </figure>

                        <t>The example of a corresponding XML snippet above describes a subVPN 
						   case where a site (SITE1) has two logical accesses (LA1 and LA2), 
						   with LA1 attached to VPNA and LA2 attached to VPNB.</t>

                     </section>

                     <section anchor="vpnpolicy" title="VPN Policy">

                        <t>The "vpn-policy" list helps express a multiVPN scenario where a
                           logical access belongs to multiple VPNs.  Multiple VPN policies can
                           be created to handle the subVPN case where each logical access is
                           part of a different set of VPNs.</t>

                        <t>As a site can belong to multiple VPNs, the vpn-policy list may be
                           composed of multiple entries.  A filter can be applied to specify
                           that only some LANs of the site should be part of a particular VPN.
                           Each time a site (or LAN) is attached to a VPN, the user must
                           precisely describe its role (site-role) within the target VPN service
                           topology.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
+--------------------------------------------------------------+
|       Site1 ------ PE7                                       |
+-------------------------+                 (VPN2)             |
                          |                                    |
+-------------------------+                                    |
|       Site2 ------ PE3               PE4 ------ Site3        |
+----------------------------------+                           |
                                   |                           |
+------------------------------------------------------------+ |
|       Site4 ------ PE5           |   PE6 ------ Site5      | |
|                                                            | |
|                      (VPN3)                                | |
+------------------------------------------------------------+ |
                                   |                           |
                                   +---------------------------+
                            ]]>
                          </artwork>
                        </figure>

                        <t>In the example above, Site5 is part of two VPNs: VPN3 and VPN2.  It
                           will play a Hub role in VPN2 and an any-to-any role in VPN3.  We can
                           express such a multiVPN scenario with the following XML snippet:</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPN2</vpn-id>
    </vpn-service>
    <vpn-service>
      <vpn-id>VPN3</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>Site5</site-id>
      <devices>
        <device>
          <device-id>D1</device-id>
        </device>
      </devices>
      <management>
        <type>provider-managed</type>
      </management>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <vpn-policies>
        <vpn-policy>
          <vpn-policy-id>POLICY1</vpn-policy-id>
          <entries>
            <id>ENTRY1</id>
            <vpn>
              <vpn-id>VPN2</vpn-id>
              <site-role>hub-role</site-role>
            </vpn>
          </entries>
          <entries>
            <id>ENTRY2</id>
            <vpn>
              <vpn-id>VPN3</vpn-id>
              <site-role>any-to-any-role</site-role>
            </vpn>
          </entries>
        </vpn-policy>
      </vpn-policies>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>LA1</site-network-access-id>
          <device-reference>D1</device-reference>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <vpn-attachment>
            <vpn-policy-id>POLICY1</vpn-policy-id>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
  </sites>
</l3vpn-svc>

                            ]]>
                          </artwork>
                        </figure>

                        <t>Now, if a more-granular VPN attachment is necessary, filtering can be
                           used.  For example, if LAN1 from Site5 must be attached to VPN2 as a
                           Hub and LAN2 must be attached to VPN3, the following configuration of 
						   corresponding XML snippet can be used:</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPN2</vpn-id>
    </vpn-service>
    <vpn-service>
      <vpn-id>VPN3</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>Site5</site-id>
      <vpn-policies>
        <vpn-policy>
          <vpn-policy-id>POLICY1</vpn-policy-id>
          <entries>
            <id>ENTRY1</id>
			<filters>
            <filter>
			  <type>lan</type>
              <lan-tag>LAN1</lan-tag>
            </filter>
			</filters>
            <vpn>
              <vpn-id>VPN2</vpn-id>
              <site-role>hub-role</site-role>
            </vpn>
          </entries>
          <entries>
            <id>ENTRY2</id>
			<filters>
            <filter>
			  <type>lan</type>
              <lan-tag>LAN2</lan-tag>
            </filter>
			</filters>
            <vpn>
              <vpn-id>VPN3</vpn-id>
              <site-role>any-to-any-role</site-role>
            </vpn>
          </entries>
        </vpn-policy>
      </vpn-policies>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>LA1</site-network-access-id>
          <vpn-attachment>
            <vpn-policy-id>POLICY1</vpn-policy-id>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
  </sites>
</l3vpn-svc>
                            ]]>
                          </artwork>
                        </figure>

                     </section>

                  </section>

               </section>

               <section anchor="deciding" title="Deciding Where to Connect the Site">

                  <t>The management system will have to determine where to connect each
                     site-network-access of a particular site to the provider network
                     (e.g., PE, aggregation switch).</t>

                  <t>The current model defines parameters and constraints that can
                     influence the meshing of the site-network-access.</t>

                  <t>The management system MUST honor all customer constraints, or if a
                     constraint is too strict and cannot be fulfilled, the management
                     system MUST NOT provision the site and MUST provide 
                     information to the user about which constraints that could not 
					 be fulfilled.How the information is provided is out of scope for 
					 this document. Whether or not to relax the constraint would 
					 then be left up to the user.</t>

                  <t>Parameters such as site location (see <xref target="location" />) 
				     and access type are just hints (see <xref target="accesstype" />)
					 for the management system for service placement.</t>

                  <t>In addition to parameters and constraints, the management system&apos;s
                     decision MAY be based on any other internal constraints that are left
                     up to the SP: least load, distance, etc.</t>

                  <section anchor="device" title="Constraint: Device">

                     <t>In the case of provider management or co-management, one or more
                        devices have been ordered by the customer to a particular 
						already-configured location.  The customer may force a particular 
						site-network-access to be connected on a particular device
                        that he ordered.</t>

                     <figure>
                       <artwork align="center">
                         <![CDATA[
  New York Site

+------------------+             Site
| +--------------+ |-----------------------------------
| | Manhattan    | |
| |           CE1********* (site-network-access#1) ******
| +--------------+ |
| +--------------+ |
| | Brooklyn  CE2********* (site-network-access#2) ******
| +--------------+ |
|                  |-----------------------------------
+------------------+
                         ]]>
                       </artwork>
                     </figure>

                     <t>In the figure above, site-network-access#1 is associated with CE1 in
                        the service request.  The SP must ensure the provisioning of this
                        connection.</t>

                   </section>

                   <section anchor="location" title="Constraint/Parameter: Site Location">

                     <t>The location information provided in this model MAY be used by a
                        management system to determine the target PE to mesh the site
                        (SP side).  A particular location must be associated with each site
                        network access when configuring it.  The SP MUST honor the
                        termination of the access on the location associated with the site
                        network access (customer side).  The "country-code" in the
                        site location SHOULD be expressed as an ISO ALPHA-2 code.</t>

                     <t>The site-network-access location is determined by the
                        "location-flavor".  In the case of a provider-managed or co-managed
                        site, the user is expected to configure a "device-reference" (device
                        case) that will bind the site-network-access to a particular device
                        that the customer ordered.  As each device is already associated with
                        a particular location, in such a case the location information is
                        retrieved from the device location.  In the case of a customer-
                        managed site, the user is expected to configure a
                        "location-reference" (location case); this provides a reference to an
                        existing configured location and will help with placement.</t>

                     <figure>
                       <artwork align="center">
                         <![CDATA[
                         POP#1 (New York)
                      +---------+
                      |   PE1   |
 Site #1 ---...       |   PE2   |
(Atlantic City)       |   PE3   |
                      +---------+

                         POP#2 (Washington)
                      +---------+
                      |   PE4   |
                      |   PE5   |
                      |   PE6   |
                      +---------+

                         POP#3 (Philadelphia)
                      +---------+
                      |   PE7   |
 Site #2 CE#1---...   |   PE8   |
(Reston)              |   PE9   |
                      +---------+
                         ]]>
                       </artwork>
                     </figure>

                     <t>In the example above, Site #1 is a customer-managed site with a
                        location L1, while Site #2 is a provider-managed site for which a CE
                        (CE#1) was ordered.  Site #2 is configured with L2 as its location.
                        When configuring a site-network-access for Site #1, the user will
                        need to reference location L1 so that the management system will know
                        that the access will need to terminate on this location.  Then, for
                        distance reasons, this management system may mesh Site #1 on a PE in
                        the Philadelphia POP.  It may also take into account resources
                        available on PEs to determine the exact target PE (e.g., least
                        loaded).  For Site #2, the user is expected to configure the
                        site-network-access with a device-reference to CE#1 so that the
                        management system will know that the access must terminate on the
                        location of CE#1 and must be connected to CE#1.  For placement of the
                        SP side of the access connection, in the case of the nearest PE used,
                        it may mesh Site #2 on the Washington POP.</t>

                  </section>

                  <section anchor="accesstype" title="Constraint/Parameter: Access Type">

                     <t>The management system needs to elect the access media to connect the
                        site to the customer (for example, xDSL, leased line, Ethernet
                        backhaul).  The customer may provide some parameters/constraints that
                        will provide hints to the management system.</t>

                     <t>The bearer container information SHOULD be the first piece of
                        information considered when making this decision:

                        <list style="symbols">

                           <t>The "requested-type" parameter provides information about the
                              media type that the customer would like to use.  If the "strict"
                              leaf is equal to "true", this MUST be considered a strict
                              constraint so that the management system cannot connect the site
                              with another media type.  If the "strict" leaf is equal to "false"
                              (default) and if the requested media type cannot be fulfilled, the
                              management system can select another media type.  The supported
                              media types SHOULD be communicated by the SP to the customer via a
                              mechanism that is out of scope for this document.</t>

                           <t>The "always-on" leaf defines a strict constraint: if set to true,
                              the management system MUST elect a media type that is "always-on"
                              (e.g., this means no dial access type).</t>

                           <t>The "bearer-reference" parameter is used in cases where the
                              customer has already ordered a network connection to the SP apart
                              from the IP VPN site and wants to reuse this connection.  The
                              string used is an internal reference from the SP and describes the
                              already-available connection.  This is also a strict requirement
                              that cannot be relaxed.  How the reference is given to the
                              customer is out of scope for this document, but as a pure example,
                              when the customer ordered the bearer (through a process that is
                              out of scope for this model), the SP may have provided the bearer
                              reference that can be used for provisioning services on top.</t>

                        </list></t>

                     <t>Any other internal parameters from the SP can also be used.  The
                        management system MAY use other parameters, such as the requested
                        "svc-input-bandwidth" and "svc-output-bandwidth", to help decide
                        which access type to use.</t>

                  </section>

                  <section anchor="accessdiversity" title="Constraint: Access Diversity">

                     <t>Each site-network-access may have one or more constraints that would
                        drive the placement of the access.  By default, the model assumes
                        that there are no constraints, but allocation of a unique bearer per
                        site-network-access is expected.</t>

                     <t>In order to help with the different placement scenarios, a
                        site-network-access may be tagged using one or multiple group
                        identifiers.  The group identifier is a string, so it can accommodate
                        both explicit naming of a group of sites (e.g., "multihomed-set1" or
                        "subVPN") and the use of a numbered identifier (e.g., 12345678).  The
                        meaning of each group-id is local to each customer administrator, and
                        the management system MUST ensure that different customers can use
                        the same group-ids.  One or more group-ids can also be defined at the
                        site level; as a consequence, all site-network-accesses under the
                        site MUST inherit the group-ids of the site they belong to.  When, in
                        addition to the site group-ids some group-ids are defined at the
                        site-network-access level, the management system MUST consider the
                        union of all groups (site level and site network access level) for
                        this particular site-network-access.</t>

                     <t>For an already-configured site-network-access, each constraint MUST
                        be expressed against a targeted set of site-network-accesses.  This
                        site-network-access MUST never be taken into account in the targeted
                        set -- for example, "My site-network-access S must not be connected
                        on the same POP as the site-network-accesses that are part of
                        Group 10."  The set of site-network-accesses against which the
                        constraint is evaluated can be expressed as a list of groups,
                        "all-other-accesses", or "all-other-groups".  The all-other-accesses
                        option means that the current site-network-access constraint MUST be
                        evaluated against all the other site-network-accesses belonging to
                        the current site.  The all-other-groups option means that the
                        constraint MUST be evaluated against all groups that the current
                        site-network-access does not belong to.</t>

                     <t>The current model defines multiple constraint-types:

                        <list style="symbols">

                           <t>pe-diverse: The current site-network-access MUST NOT be connected
                              to the same PE as the targeted site-network-accesses.</t>

                           <t>pop-diverse: The current site-network-access MUST NOT be connected
                              to the same POP as the targeted site-network-accesses.</t>

                           <t>linecard-diverse: The current site-network-access MUST NOT be
                              connected to the same linecard as the targeted
                              site-network-accesses.</t>

                           <t>bearer-diverse: The current site-network-access MUST NOT use
                              common bearer components compared to bearers used by the targeted
                              site-network-accesses.  "bearer-diverse" provides some level of
                              diversity at the access level.  As an example, two bearer-diverse
                              site-network-accesses must not use the same DSLAM, BAS, or Layer 2
                              switch.</t>

                           <t>same-pe: The current site-network-access MUST be connected to the
                              same PE as the targeted site-network-accesses.</t>

                           <t>same-bearer: The current site-network-access MUST be connected
                              using the same bearer as the targeted site-network-accesses.</t>

                        </list></t>

                     <t>These constraint-types can be extended through augmentation.</t>

                     <t>Each constraint is expressed as "The site-network-access S must be
                        &lt;constraint-type&gt; (e.g., pe-diverse, pop-diverse) from 
						these &lt;target&gt; site-network-accesses."</t>

                     <t>The group-id used to target some site-network-accesses may be the
                        same as the one used by the current site-network-access.  This eases
                        the configuration of scenarios where a group of site-network-access
                        points has a constraint between the access points in the group.  As
                        an example, if we want a set of sites (Site#1 to Site#5) to be
                        connected on different PEs, we can tag them with the same group-id
                        and express a pe-diverse constraint for this group-id with the 
						following XML snippet: </t>

                     <figure>
                       <artwork align="center">
                         <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <management>
        <type>customer-managed</type>
      </management>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>10</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pe-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>10</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
    <site>
      <site-id>SITE2</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <management>
        <type>customer-managed</type>
      </management>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>10</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pe-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>10</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
	...
    <site>
      <site-id>SITE5</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <management>
        <type>customer-managed</type>
      </management>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>10</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pe-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>10</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
  </sites>
</l3vpn-svc>
                         ]]>
                       </artwork>
                     </figure>

                     <t>The group-id used to target some site-network-accesses may also be
                        different than the one used by the current site-network-access.  This
                        can be used to express that a group of sites has some constraints
                        against another group of sites, but there is no constraint within the
                        group.  For example, we consider a set of six sites and two groups;
                        we want to ensure that a site in the first group must be pop-diverse
                        from a site in the second group. The example of a corresponding XML 
						snippet is described as follows:</t>

                     <figure>
                       <artwork align="center">
                         <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <access-diversity>
            <groups>
              <group>
                <group-id>10</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pop-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>20</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
    <site>
      <site-id>SITE2</site-id>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <access-diversity>
            <groups>
              <group>
                <group-id>10</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pop-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>20</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
	...
    <site>
      <site-id>SITE5</site-id>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <access-diversity>
            <groups>
              <group>
                <group-id>20</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pop-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>10</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
    <site>
      <site-id>SITE6</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <management>
        <type>customer-managed</type>
      </management>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>20</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pop-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>10</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
  </sites>
</l3vpn-svc>
                         ]]>
                       </artwork>
                     </figure>

                  </section>

                  <section anchor="infeasible" title="Infeasible Access Placement">

                     <t>Some infeasible access placement scenarios could be created via the
                        proposed configuration framework.  Such infeasible access placement
                        scenarios could result from constraints that are too restrictive,
                        leading to infeasible access placement in the network or conflicting
                        constraints that would also lead to infeasible access placement.  An
                        example of conflicting rules would be to request that
                        site-network-access#1 be pe-diverse from site-network-access#2 and to
                        request at the same time that site-network-access#2 be on the same PE
                        as site-network-access#1.  When the management system cannot
                        determine the placement of a site-network-access, it MUST return an
                        error message indicating that placement was not possible.</t>

                  </section>

                  <section anchor="egaccess" title="Examples of Access Placement">

                     <section anchor="multihome" title="Multihoming">

                        <t>The customer wants to create a multihomed site.  The site will be
                           composed of two site-network-accesses; for resiliency purposes, the
                           customer wants the two site-network-accesses to be meshed on
                           different POPs.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
                                        POP#1
+-------+                            +---------+
|       |                            |   PE1   |
|       |---site-network-access#1----|   PE2   |
|       |                            |   PE3   |
|       |                            +---------+
| Site#1|
|       |                               POP#2
|       |                            +---------+
|       |                            |   PE4   |
|       |---site-network-access#2----|   PE5   |
|       |                            |   PE6   |
|       |                            +---------+
+-------+
                            ]]>
                          </artwork>
                        </figure>

                        <t>This scenario can be expressed with the following XML snippet:</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <management>
        <type>customer-managed</type>
      </management>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>10</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pop-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>20</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
        <site-network-access>
          <site-network-access-id>2</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>20</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pop-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>10</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
  </sites>
</l3vpn-svc>
                            ]]>
                          </artwork>
                        </figure>

                        <t>But it can also be expressed with the following XML snippet:</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <access-diversity>
            <constraints>
              <constraint>
                <constraint-type>pop-diverse</constraint-type>
                <target>
                  <all-other-accesses/>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
        <site-network-access>
          <site-network-access-id>2</site-network-access-id>
          <access-diversity>
            <constraints>
              <constraint>
                <constraint-type>pop-diverse</constraint-type>
                <target>
                  <all-other-accesses/>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
  </sites>
</l3vpn-svc>
                            ]]>
                          </artwork>
                        </figure>

                     </section>

                     <section anchor="offload" title="Site Offload">

                        <t>The customer has six branch offices in a particular region, and he
                           wants to prevent having all branch offices connected on the same PE.
						   </t>

                        <t>He wants to express that three branch offices cannot be connected on
                           the same linecard.  Also, the other branch offices must be connected
                           on a different POP.  Those other branch offices cannot also be
                           connected on the same linecard.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
                         POP#1
                      +---------+
                      |   PE1   |
Office#1 ---...       |   PE2   |
Office#2 ---...       |   PE3   |
Office#3 ---...       |   PE4   |
                      +---------+

                         POP#2
                      +---------+
Office#4 ---...       |   PE5   |
Office#5 ---...       |   PE6   |
Office#6 ---...       |   PE7   |
                      +---------+
                            ]]>
                          </artwork>
                        </figure>

                        <t>This scenario can be expressed as follows:

                           <list style="symbols">

                              <t>We need to create two groups of sites: Group#10, which is composed
                                 of Office#1, Office#2, and Office#3; and Group#20, which is
                                 composed of Office#4, Office#5, and Office#6.</t>

                              <t>Sites within Group#10 must be pop-diverse from sites within
                                 Group#20, and vice versa.</t>

                              <t>Sites within Group#10 must be linecard-diverse from other sites in
                                 Group#10 (same for Group#20).</t>

                           </list></t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>Office1</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <management>
        <type>customer-managed</type>
      </management>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>10</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pop-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>20</group-id>
                  </group>
                </target>
              </constraint>
              <constraint>
                <constraint-type>linecard-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>10</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
    <site>
      <site-id>Office2</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <management>
        <type>customer-managed</type>
      </management>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>10</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pop-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>20</group-id>
                  </group>
                </target>
              </constraint>
              <constraint>
                <constraint-type>linecard-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>10</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
    <site>
      <site-id>Office3</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <management>
        <type>customer-managed</type>
      </management>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>10</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pop-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>20</group-id>
                  </group>
                </target>
              </constraint>
              <constraint>
                <constraint-type>linecard-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>10</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
    <site>
      <site-id>Office4</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <management>
        <type>customer-managed</type>
      </management>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>20</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pop-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>10</group-id>
                  </group>
                </target>
              </constraint>
              <constraint>
                <constraint-type>linecard-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>20</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
    <site>
      <site-id>Office5</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <management>
        <type>customer-managed</type>
      </management>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>20</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pop-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>10</group-id>
                  </group>
                </target>
              </constraint>
              <constraint>
                <constraint-type>linecard-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>20</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
    <site>
      <site-id>Office6</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <management>
        <type>customer-managed</type>
      </management>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>20</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pop-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>10</group-id>
                  </group>
                </target>
              </constraint>
              <constraint>
                <constraint-type>linecard-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>20</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
  </sites>
</l3vpn-svc>
                            ]]>
                          </artwork>
                        </figure>

                     </section>

                     <section anchor="parallel" title="Parallel Links">

                        <t>To increase its site bandwidth at lower cost, a customer wants to
                           order two parallel site-network-accesses that will be connected to
                           the same PE.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
       *******site-network-access#1**********
Site 1 *******site-network-access#2********** PE1
                            ]]>
                          </artwork>
                        </figure>

                        <t>This scenario can be expressed with the following XML snippet:</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNB</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <access-diversity>
            <groups>
              <group>
                <group-id>PE-linkgrp-1</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>same-pe</constraint-type>
                <target>
                  <group>
                    <group-id>PE-linkgrp-1</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNB</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
        <site-network-access>
          <site-network-access-id>2</site-network-access-id>
          <access-diversity>
            <groups>
              <group>
                <group-id>PE-linkgrp-1</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>same-pe</constraint-type>
                <target>
                  <group>
                    <group-id>PE-linkgrp-1</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNB</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
  </sites>
</l3vpn-svc>
                            ]]>
                          </artwork>
                        </figure>

                     </section>

                     <section anchor="subvpnparallel" title="SubVPN with Multihoming">

                        <t>A customer has a site that is dual-homed.  The dual-homing must be
                           done on two different PEs.  The customer also wants to implement two
                           subVPNs on those multihomed accesses.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
+-----------------+         Site                     +------+
|                 |---------------------------------/       +-----+
|                 |****(site-network-access#1)*****| VPN B /       \
| New York Office |****(site-network-access#2)************| VPN C   |
|                 |                                  +-----\       /
|                 |                                         +-----+
|                 |
|                 |                                  +------+
|                 |                                 /       +-----+
|                 |****(site-network-access#3)*****| VPN B /       \
|                 |****(site-network-access#4)************| VPN C   |
|                 |                                  +-----\       /
|                 |-----------------------------------      +-----+
+-----------------+
                            ]]>
                          </artwork>
                        </figure>

                        <t>This scenario can be expressed as follows:
                           <list style="symbols">

                              <t>The site will have four site network accesses (two subVPNs coupled
                                 via dual-homing).</t>

                              <t>Site-network-access#1 and site-network-access#3 will correspond to
                                 the multihoming of subVPN B.  A PE-diverse constraint is required
                                 between them.</t>

                              <t>Site-network-access#2 and site-network-access#4 will correspond to
                                 the multihoming of subVPN C.  A PE-diverse constraint is required
                                 between them.</t>

                              <t>To ensure proper usage of the same bearer for the subVPN,
                                 site-network-access#1 and site-network-access#2 must share the
                                 same bearer as site-network-access#3 and site-network-access#4.</t>
                           </list></t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNB</vpn-id>
    </vpn-service>
    <vpn-service>
      <vpn-id>VPNC</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <management>
        <type>customer-managed</type>
      </management>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>dualhomed-1</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pe-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>dualhomed-2</group-id>
                  </group>
                </target>
              </constraint>
              <constraint>
                <constraint-type>same-bearer</constraint-type>
                <target>
                  <group>
                    <group-id>dualhomed-1</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNB</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
        <site-network-access>
          <site-network-access-id>2</site-network-access-id>
          <access-diversity>
            <groups>
              <group>
                <group-id>dualhomed-1</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pe-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>dualhomed-2</group-id>
                  </group>
                </target>
              </constraint>
              <constraint>
                <constraint-type>same-bearer</constraint-type>
                <target>
                  <group>
                    <group-id>dualhomed-1</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNC</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
        <site-network-access>
          <site-network-access-id>3</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>dualhomed-2</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pe-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>dualhomed-1</group-id>
                  </group>
                </target>
              </constraint>
              <constraint>
                <constraint-type>same-bearer</constraint-type>
                <target>
                  <group>
                    <group-id>dualhomed-2</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNB</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
        <site-network-access>
          <site-network-access-id>4</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>dualhomed-2</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pe-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>dualhomed-1</group-id>
                  </group>
                </target>
              </constraint>
              <constraint>
                <constraint-type>same-bearer</constraint-type>
                <target>
                  <group>
                    <group-id>dualhomed-2</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <vpn-attachment>
            <vpn-id>VPNC</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
    </site>
  </sites>
</l3vpn-svc>
                            ]]>
                          </artwork>
                        </figure>

                     </section>

                  </section>

                  <section anchor="rdnvrf" title="Route Distinguisher and VRF Allocation">

                     <t>The route distinguisher (RD) is a critical parameter of PE-based
                        L3VPNs as described in <xref target="RFC4364" /> that provides the ability to
                        distinguish common addressing plans in different VPNs.  As for route
                        targets (RTs), a management system is expected to allocate a VRF on
                        the target PE and an RD for this VRF.</t>

                     <t>If a VRF already exists on the target PE and the VRF fulfills the
                        connectivity constraints for the site, there is no need to recreate
                        another VRF, and the site MAY be meshed within this existing VRF.
                        How the management system checks that an existing VRF fulfills the
                        connectivity constraints for a site is out of scope for this
                        document.</t>

                     <t>If no such VRF exists on the target PE, the management system has to
                        initiate the creation of a new VRF on the target PE and has to
                        allocate a new RD for this new VRF.</t>

                     <t>The management system MAY apply a per-VPN or per-VRF allocation
                        policy for the RD, depending on the SP&apos;s policy.  In a per-VPN
                        allocation policy, all VRFs (dispatched on multiple PEs) within a VPN
                        will share the same RD value.  In a per-VRF model, all VRFs should
                        always have a unique RD value.  Some other allocation policies are
                        also possible, and this document does not restrict the allocation
                        policies to be used.</t>

                     <t>The allocation of RDs MAY be done in the same way as RTs.  The
                        examples provided in <xref target="rt" /> could be reused in this
                        scenario.</t>

                     <t>Note that an SP MAY configure a target PE for an automated allocation
                        of RDs.  In this case, there will be no need for any backend system
                        to allocate an RD value.</t>

                  </section>

               </section>

               <section anchor="availability" title="Site Network Access Availability">

                  <t>A site may be multihomed, meaning that it has multiple
                     site-network-access points.  Placement constraints defined in
                     previous sections will help ensure physical diversity.</t>

                  <t>When the site-network-accesses are placed on the network, a customer
                     may want to use a particular routing policy on those accesses.</t>

                  <t>The "site-network-access/availability" container defines parameters
                     for site redundancy.  The "access-priority" leaf defines a preference
                     for a particular access.  This preference is used to model
                     load-balancing or primary/backup scenarios.  The higher the
                     access-priority value, the higher the preference will be.</t>

                  <t>The figure below describes how the access-priority attribute can be
                     used.</t>

                  <figure>
                    <artwork align="center">
                      <![CDATA[
Hub#1 LAN (Primary/backup)          Hub#2 LAN (Load-sharing)
  |                                                     |
  |    access-priority 1          access-priority 1     |
  |--- CE1 ------- PE1            PE3 --------- CE3 --- |
  |                                                     |
  |                                                     |
  |--- CE2 ------- PE2            PE4 --------- CE4 --- |
  |    access-priority 2          access-priority 1     |

                          PE5
                           |
                           |
                           |
                          CE5
                           |
                      Spoke#1 site (Single-homed)
                      ]]>
                    </artwork>
                  </figure>

                  <t>In the figure above, Hub#2 requires load-sharing, so all the
                     site-network-accesses must use the same access-priority value.  On
                     the other hand, as Hub#1 requires a primary site-network-access and a
                     backup site-network-access, a higher access-priority setting will be
                     configured on the primary site-network-access.</t>

                  <t>Scenarios that are more complex can be modeled.  Let&apos;s consider
                     a Hub site with five accesses to the network (A1,A2,A3,A4,A5).  The
                     customer wants to load-share its traffic on A1,A2 in the nominal
                     situation.  If A1 and A2 fail, the customer wants to load-share its
                     traffic on A3 and A4; finally, if A1 to A4 are down, he wants to
                     use A5.  We can model this easily by configuring the following
                     access-priority values: A1=100, A2=100, A3=50, A4=50, A5=10.</t>

                  <t>The access-priority scenario has some limitations.  An
                     access-priority scenario like the previous one with five accesses but
                     with the constraint of having traffic load-shared between A3 and A4
                     in the case where A1 OR A2 is down is not achievable.  But the
                     authors believe that using the access-priority attribute will cover
                     most of the deployment use cases and that the model can still be
                     extended via augmentation to support additional use cases.</t>

               </section>

               <section anchor="trafprot" title="Traffic Protection">

                  <t>The service model supports the ability to protect the traffic for a
                     site.  Such protection provides a better level of availability in
                     multihoming scenarios by, for example, using local-repair techniques
                     in case of failures.  The associated level of service guarantee would
                     be based on an agreement between the customer and the SP and is out
                     of scope for this document.</t>

                  <figure>
                    <artwork align="center">
                      <![CDATA[
    Site#1                            Site#2
CE1 ----- PE1 -- P1            P3 -- PE3 ---- CE3
 |                              |             |
 |                              |             |
CE2 ----- PE2 -- P2            P4 -- PE4 ---- CE4
          /
         /
CE5 ----+
   Site#3
                      ]]>
                    </artwork>
                  </figure>

                  <t>In the figure above, we consider an IP VPN service with three sites,
                     including two dual-homed sites (Site#1 and Site#2).  For dual-homed
                     sites, we consider PE1-CE1 and PE3-CE3 as primary and PE2-CE2,PE4-CE4
                     as backup for the example (even if protection also applies to
                     load-sharing scenarios).</t>

                  <t>In order to protect Site#2 against a failure, a user may set the
                     "traffic-protection/enabled" leaf to true for Site#2.  How the
                     traffic protection will be implemented is out of scope for this
                     document.  However, in such a case, we could consider traffic coming
                     from a remote site (Site#1 or Site#3), where the primary path would
                     use PE3 as the egress PE.  PE3 may have preprogrammed a backup
                     forwarding entry pointing to the backup path (through PE4-CE4) for
                     all prefixes going through the PE3-CE3 link.  How the backup path is
                     computed is out of scope for this document.  When the PE3-CE3 link
                     fails, traffic is still received by PE3, but PE3 automatically
                     switches traffic to the backup entry; the path will therefore be
                     PE1-P1-(...)-P3-PE3-PE4-CE4 until the remote PEs reconverge and use
                     PE4 as the egress PE.</t>

               </section>

               <section anchor="sec" title="Security">

                  <t>The "security" container defines customer-specific security
                     parameters for the site.  The security options supported in the model
                     are limited but may be extended via augmentation.</t>

                  <section anchor="auth" title="Authentication">

                     <t>The current model does not support any authentication parameters for
                        the site connection, but such parameters may be added in the
                        "authentication" container through augmentation.</t>

                  </section>

                  <section anchor="enc" title="Encryption">

                     <t>Traffic encryption can be requested on the connection.  It may be
                        performed at Layer 2 or Layer 3 by selecting the appropriate
                        enumeration in the "layer" leaf.  For example, an SP may use IPsec
                        when a customer requests Layer 3 encryption.  The encryption profile
                        can be SP defined or customer specific.</t>

                     <t>When an SP profile is used and a key (e.g., a pre-shared key) is
                        allocated by the provider to be used by a customer, the SP should
                        provide a way to communicate the key in a secured way to the
                        customer.</t>

                     <t>When a customer profile is used, the model supports only a pre-shared
                        key for authentication, with the pre-shared key provided through the
                        NETCONF or RESTCONF request.  A secure channel must be used to ensure
                        that the pre-shared key cannot be intercepted.</t>

                     <t>For security reasons, it may be necessary for the customer to change
                        the pre-shared key on a regular basis.  To perform a key change, the
                        user can ask the SP to change the pre-shared key by submitting a new
                        pre-shared key for the site configuration (as shown below with a 
						corresponding XML snippet). This mechanism might not be hitless. </t>

                     <figure>
                       <artwork align="center">
                         <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <security>
            <encryption>
              <encryption-profile>
                <preshared-key>MY_NEW_KEY</preshared-key>
              </encryption-profile>
            </encryption>
          </security>
        </site-network-access>
      </site-network-accesses>
    </site>
  </sites>
</l3vpn-svc>

                         ]]>
                       </artwork>
                     </figure>

                     <t>A hitless key-change mechanism may be added through augmentation.</t>

                     <t>Other key-management methodologies (e.g., PKI) may be added 
					 through augmentation. </t>

                  </section>

                  </section>

                  <section anchor="manage" title="Management">

                     <t>The model defines three types of common management options:

                        <list style="symbols">

                           <t>provider-managed: The CE router is managed only by the provider.
                              In this model, the responsibility boundary between the SP and the
                              customer is between the CE and the customer network.</t>

                           <t>customer-managed: The CE router is managed only by the customer.
                              In this model, the responsibility boundary between the SP and the
                              customer is between the PE and the CE.</t>

                           <t>co-managed: The CE router is primarily managed by the provider; in
                              addition, the SP allows customers to access the CE for
                              configuration/monitoring purposes.  In the co-managed mode, the
                              responsibility boundary is the same as the responsibility boundary
                              for the provider-managed model.</t>

                        </list></t>

                     <t>Based on the management model, different security options MAY be
                        derived.</t>

                     <t>In the co-managed case, the model defines options for the
                        management address family (IPv4 or IPv6) and the associated
                        management address.</t>

                  </section>

                  <section anchor="rtgprot" title="Routing Protocols">

                     <t>"routing-protocol" defines which routing protocol must be activated
                        between the provider and the customer router.  The current model
                        supports the following settings: bgp, rip, ospf, static, direct,
                        and vrrp.</t>

                     <t>The routing protocol defined applies at the provider-to-customer
                        boundary.  Depending on how the management model is administered, it
                        may apply to the PE-CE boundary or the CE-to-customer boundary.  In
                        the case of a customer-managed site, the routing protocol defined
                        will be activated between the PE and the CE router managed by the
                        customer.  In the case of a provider-managed site, the routing
                        protocol defined will be activated between the CE managed by the SP
                        and the router or LAN belonging to the customer.  In this case, we
                        expect the PE-CE routing to be configured based on the SP&apos;s rules, as
                        both are managed by the same entity.</t>

                     <figure>
                       <artwork align="center">
                         <![CDATA[
                        Rtg protocol
192.0.2.0/24 ----- CE ----------------- PE1

             Customer-managed site

      Rtg protocol
Customer router ----- CE ----------------- PE1

             Provider-managed site
                         ]]>
                       </artwork>
                     </figure>

                     <t>All the examples below will refer to a scenario for a customer-
                        managed site.</t>

                     <section anchor="dualstack" title="Handling of Dual Stack">

                        <t>All routing protocol types support dual stack by using the
                           "address-family" leaf-list.</t>

                        <t>Example of a corresponding XML snippet with dual stack using 
						the same routing protocol:</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <routing-protocols>
        <routing-protocol>
          <type>static</type>
          <static>
			<cascaded-lan-prefixes>
            <ipv4-lan-prefixes>
            <lan>192.0.2.0/24</lan>
            <next-hop>203.0.113.1</next-hop>
            </ipv4-lan-prefixes>
            </cascaded-lan-prefixes>
          </static>
        </routing-protocol>
      </routing-protocols>
    </site>
  </sites>
</l3vpn-svc>
                            ]]>
                          </artwork>
                        </figure>

                        <t>Example of a corresponding XML snippet with dual stack using 
						two different routing protocols:</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <routing-protocols>
        <routing-protocol>
          <type>rip</type>
          <rip>
            <address-family>ipv4</address-family>
          </rip>
        </routing-protocol>
        <routing-protocol>
          <type>ospf</type>
          <ospf>
            <address-family>ipv6</address-family>
            <area-address>4.4.4.4</area-address>
          </ospf>
        </routing-protocol>
      </routing-protocols>
    </site>
  </sites>
</l3vpn-svc>
                            ]]>
                          </artwork>
                        </figure>

                     </section>

                     <section anchor="lanconn" title="LAN Directly Connected to SP Network">

                        <t>The routing protocol type "direct" SHOULD be used when a customer LAN
                           is directly connected to the provider network and must be advertised
                           in the IP VPN.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
LAN attached directly to provider network:

192.0.2.0/24 ----- PE1
                            ]]>
                          </artwork>
                        </figure>

                        <t>In this case, the customer has a default route to the PE address.</t>

                     </section>

                     <section anchor="lanconnred" title="LAN Directly Connected to SP Network with Redundancy">

                        <t>The routing protocol type "vrrp" SHOULD be used and advertised in the
                           IP VPN when

                           <list style="symbols">

                              <t>the customer LAN is directly connected to the provider network,
                                 and</t>

                              <t>LAN redundancy is expected.</t>

                           </list></t>

                        <t>LAN attached directly to provider network with LAN redundancy:</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
192.0.2.0/24 ------ PE1
               |
               +--- PE2
                            ]]>
                          </artwork>
                        </figure>

                        <t>In this case, the customer has a default route to the SP network.</t>

                     </section>

                     <section anchor="staticrtg" title="Static Routing">

                        <t>The routing protocol type "static" MAY be used when a customer LAN is
                           connected to the provider network through a CE router and must be
                           advertised in the IP VPN.  In this case, the static routes give next
                           hops (nh) to the CE and to the PE.  The customer has a default route
                           to the SP network.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
                         Static rtg
192.0.2.0/24 ------ CE -------------- PE
                     |                |
                     |      Static route 192.0.2.0/24 nh CE
     Static route 0.0.0.0/0 nh PE
                            ]]>
                          </artwork>
                        </figure>

                     </section>

                     <section anchor="rip" title="RIP Routing">

                        <t>The routing protocol type "rip" MAY be used when a customer LAN is
                           connected to the provider network through a CE router and must be
                           advertised in the IP VPN.  For IPv4, the model assumes that RIP
                           version 2 is used.</t>

                        <t>In the case of dual-stack routing requested through this model, the
                           management system will be responsible for configuring RIP (including
                           the correct version number) and associated address families on
                           network elements.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
                        RIP rtg
192.0.2.0/24 ------ CE -------------- PE
                             ]]>
                          </artwork>
                        </figure>

                     </section>

                     <section anchor="ospf" title="OSPF Routing">

                        <t>The routing protocol type "ospf" MAY be used when a customer LAN is
                           connected to the provider network through a CE router and must be
                           advertised in the IP VPN.</t>

                        <t>It can be used to extend an existing OSPF network and interconnect
                           different areas.  See <xref target="RFC4577" /> for more details.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
                         +---------------------+
                         |                     |
                 OSPF    |                     | OSPF
                 area 1  |                     | area 2
(OSPF                    |                     |          (OSPF
area 1) --- CE ---------- PE               PE ----- CE --- area 2)
                         |                     |
                         +---------------------+
                            ]]>
                          </artwork>
                        </figure>

                        <t>The model also defines an option to create an OSPF sham link between
                           two sites sharing the same area and having a backdoor link.  The
                           sham link is created by referencing the target site sharing the same
                           OSPF area.  The management system will be responsible for checking to
                           see if there is already a sham link configured for this VPN and area
                           between the same pair of PEs.  If there is no existing sham link, the
                           management system will provision one.  This sham link MAY be reused
                           by other sites.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
 +------------------------+
 |                        |
 |                        |
 |  PE (--sham link--)PE  |
 |    |                |  |
 +----|----------------|--+
      | OSPF area 1    | OSPF area 1
      |                |
      CE1             CE2
      |                |
(OSPF area 1)     (OSPF area 1)
      |                |
      +----------------+
                            ]]>
                          </artwork>
                        </figure>

                        <t>Regarding dual-stack support, the user MAY specify both IPv4 and IPv6
                           address families, if both protocols should be routed through OSPF.
                           As OSPF uses separate protocol instances for IPv4 and IPv6, the
                           management system will need to configure both OSPF version 2 and OSPF
                           version 3 on the PE-CE link.</t>
                        <t>Other OSPF parameters, such as timers, are typically set by the SP and
                           communicated to the customer outside the scope of this model.</t>
                        <t>Example of a corresponding XML snippet with OSPF routing parameters 
						   in the service model:</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <routing-protocols>
        <routing-protocol>
          <type>ospf</type>
          <ospf>
            <area-address>0.0.0.1</area-address>
            <address-family>ipv4</address-family>
            <address-family>ipv6</address-family>
          </ospf>
        </routing-protocol>
      </routing-protocols>
    </site>
  </sites>
</l3vpn-svc>
                            ]]>
                          </artwork>
                        </figure>

                        <t>Example of PE configuration done by the management system:</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
router ospf 10
 area 0.0.0.1
  interface Ethernet0/0
!
router ospfv3 10
 area 0.0.0.1
  interface Ethernet0/0
 !
                            ]]>
                          </artwork>
                        </figure>

                     </section>

                     <section anchor="bgp" title="BGP Routing">

                        <t>The routing protocol type "bgp" MAY be used when a customer LAN is
                           connected to the provider network through a CE router and must be
                           advertised in the IP VPN.</t>

                        <figure>
                          <artwork align="center">
                            <![CDATA[
                          BGP rtg
192.0.2.0/24 ------ CE -------------- PE
                            ]]>
                          </artwork>
                        </figure>

                        <t>The session addressing will be derived from connection parameters as
                           well as the SP&apos;s knowledge of the addressing plan that is in use.</t>

                        <t>In the case of dual-stack access, the user MAY request BGP routing
                           for both IPv4 and IPv6 by specifying both address families.  It will
                           be up to the SP and management system to determine how to describe the
                           configuration (two BGP sessions, single, multi-session, etc.). This, 
						   along with other BGP parameters such as timers, is communicated to
                           the customer outside the scope of this model.</t>

                        <t>The service configuration below activates BGP on the PE-CE link for
                           both IPv4 and IPv6.</t>

                        <t>BGP activation requires the SP to know the address of the customer
                           peer.  If the site-network-access connection addresses are used for
                           BGP peering, the "static-address" allocation type for the IP connection 
                           MUST be used.  Other peering mechanisms are outside the scope of
                           this model. An example of a corresponding XML snippet is described
						   as follows:</t>

                         <figure>
                           <artwork align="center">
                             <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <routing-protocols>
        <routing-protocol>
          <type>bgp</type>
          <bgp>
            <autonomous-system>65000</autonomous-system>
            <address-family>ipv4</address-family>
            <address-family>ipv6</address-family>
          </bgp>
        </routing-protocol>
      </routing-protocols>
    </site>
  </sites>
</l3vpn-svc>
                             ]]>
                           </artwork>
                         </figure>

                         <t>Depending on the SP flavor, a management system can divide this
                            service configuration into different flavors, as shown by the
                            following examples.</t>

                         <t>Example of PE configuration done by the management system
                            (single IPv4 transport session):</t>

                         <figure>
                           <artwork align="center">
                             <![CDATA[
router bgp 100
 neighbor 203.0.113.2 remote-as 65000
 address-family ipv4 vrf Cust1
    neighbor 203.0.113.2 activate
 address-family ipv6 vrf Cust1
    neighbor 203.0.113.2 activate
    neighbor 203.0.113.2 route-map SET-NH-IPV6 out
                             ]]>
                           </artwork>
                         </figure>

                         <t>Example of PE configuration done by the management system
                            (two sessions):</t>

                         <figure>
                           <artwork align="center">
                             <![CDATA[
router bgp 100
 neighbor 203.0.113.2 remote-as 65000
 neighbor 2001::2 remote-as 65000
 address-family ipv4 vrf Cust1
    neighbor 203.0.113.2 activate
 address-family ipv6 vrf Cust1
    neighbor 2001::2 activate
                             ]]>
                           </artwork>
                         </figure>

                         <t>Example of PE configuration done by the management system
                            (multi-session):</t>

                         <figure>
                           <artwork align="center">
                             <![CDATA[
router bgp 100
 neighbor 203.0.113.2 remote-as 65000
 neighbor 203.0.113.2 multisession per-af
 address-family ipv4 vrf Cust1
    neighbor 203.0.113.2 activate
 address-family ipv6 vrf Cust1
    neighbor 203.0.113.2 activate
    neighbor 203.0.113.2 route-map SET-NH-IPV6 out
                             ]]>
                           </artwork>
                         </figure>

                      </section>

                   </section>

                   <section anchor="service" title="Service">

                      <t>The service defines service parameters associated with the site.</t>

                      <section anchor="bw" title="Bandwidth">

                         <t>The service bandwidth refers to the bandwidth requirement between the
                            PE and the CE (WAN link bandwidth).  The requested bandwidth is
                            expressed as svc-input-bandwidth and svc-output-bandwidth in bits
                            per second.  The input/output direction uses the customer site as a
                            reference: "input bandwidth" means download bandwidth for the site,
                            and "output bandwidth" means upload bandwidth for the site.</t>

                         <t>The service bandwidth is only configurable at the site-network-access
                            level.</t>

                         <t>Using a different input and output bandwidth will allow the SP to
                            determine if the customer allows for asymmetric bandwidth access,
                            such as ADSL.  It can also be used to set rate-limiting in a
                            different way for uploading and downloading on a symmetric bandwidth
                            access.</t>

                         <t>The bandwidth is a service bandwidth expressed primarily as IP
                            bandwidth, but if the customer enables MPLS for Carriers&apos; Carriers
                            (CsC), this becomes MPLS bandwidth.</t>

                      </section>
					  
				   <section anchor="mtu" title="MTU">
				         <t>The service MTU refers to the maximum PDU size that the customer may use. 
						    If the customer sends packets which are longer than the requested service
							MTU, the network may discard it (or for IPv4, fragmented).</t>
				   </section>

                      <section anchor="qos" title="QoS">

                         <t>The model defines QoS parameters in an abstracted way:

                            <list style="symbols">

                               <t>qos-classification-policy: policy that defines a set of ordered
                                  rules to classify customer traffic.</t>

                               <t>qos-profile: QoS scheduling profile to be applied.</t>

                            </list></t>

                         <section anchor="qosclass" title="QoS Classification">

                            <t>QoS classification rules are handled by the
                               "qos-classification-policy" container.  The qos-classification-policy
                               container is an ordered list of rules that match a flow or
                               application and set the appropriate target class of service
                               (target-class-id).  The user can define the match using an
                               application reference or a flow definition that is more specific
                               (e.g., based on Layer 3 source and destination addresses, Layer 4
                               ports, and Layer 4 protocol).  When a flow definition is used, the
                               user can employ a "target-sites" leaf-list to identify the
                               destination of a flow rather than using destination IP addresses.  In
                               such a case, an association between the site abstraction and the IP
                               addresses used by this site must be done dynamically.  How this
                               association is done is out of scope for this document. The association 
							   of a site to an IP VPN is done through the "vpn-attachment" container. 
							   Therefore the user can also employ "target-sites" leaf-list and 
							   "vpn-attachment" to identify the destination of a flow targeted to 
							   specific vpn service. A rule that does not have a match statement is 
							   considered a match-all rule. An SP may implement a default terminal 
							   classification rule if the customer does not provide it.  It will be 
							   up to the SP to determine its default target class. The current model 
							   defines some applications, but new application identities may be added 
							   through augmentation. The exact meaning of each application identity 
							   is up to the SP, so it will be necessary for the SP to advise the 
							   customer on the usage of application matching.</t>

                            <t>Where the classification is done depends on the SP&apos;s implementation
                               of the service, but classification concerns the flow coming from the
                               customer site and entering the network.</t>

                            <figure>
                              <artwork align="center">
                                <![CDATA[
                               Provider network
                          +-----------------------+
   192.0.2.0/24
198.51.100.0/24 ---- CE --------- PE

  Traffic flow
 ---------->
                                ]]>
                              </artwork>
                            </figure>

                            <t>In the figure above, the management system should implement the
                               classification rule:

                               <list style="symbols">

                                  <t>in the ingress direction on the PE interface, if the CE is
                                     customer-managed.</t>

                                  <t>in the ingress direction on the CE interface connected to the
                                     customer LAN, if the CE is provider-managed.</t>

                               </list></t>

                            <t>The figure below describes a sample service description of QoS
                               classification for a site:</t>

                            <figure>
                              <artwork align="center">
                                <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <service>
        <qos>
          <qos-classification-policy>
            <rule>
              <id>SvrA-http</id>
              <match-flow>
                <ipv4-src-prefix>192.0.2.0/24</ipv4-src-prefix>
                <ipv4-dst-prefix>203.0.113.1/32</ipv4-dst-prefix>
                <l4-dst-port>80</l4-dst-port>
                <protocol-type>tcp</protocol-type>
              </match-flow>
              <target-class-id>DATA2</target-class-id>
            </rule>
            <rule>
              <id>SvrA-ftp</id>
              <match-flow>
                <ipv4-src-prefix>192.0.2.0/24</ipv4-src-prefix>
                <ipv4-dst-prefix>203.0.113.1/32</ipv4-dst-prefix>
                <l4-dst-port>21</l4-dst-port>
                <protocol-field>tcp</protocol-field>
              </match-flow>
              <target-class-id>DATA2</target-class-id>
            </rule>
            <rule>
              <id>p2p</id>
              <match-application>p2p</match-application>
              <target-class-id>DATA3</target-class-id>
            </rule>
            <rule>
              <id>any</id>
              <target-class-id>DATA1</target-class-id>
            </rule>
          </qos-classification-policy>
        </qos>
      </service>
    </site>
  </sites>
</l3vpn-svc>
                                ]]>
                              </artwork>
                            </figure>

                            <t>In the example above:

                               <list style="symbols">

                                  <t>HTTP traffic from the 192.0.2.0/24 LAN destined for 203.0.113.1/32
                                     will be classified in DATA2.</t>

                                  <t>FTP traffic from the 192.0.2.0/24 LAN destined for 203.0.113.1/32
                                     will be classified in DATA2.</t>

                                  <t>Peer-to-peer traffic will be classified in DATA3.</t>

                                  <t>All other traffic will be classified in DATA1.</t>

                               </list></t>

                            <t>The order of rule list entries is defined by the user. 
							   The management system responsible for translating 
							   those rules in network element configuration MUST keep 
							   the same processing order in network element configuration. </t>

                         </section>

                         <section anchor="qosprofile" title="QoS Profile">

                            <t>The user can choose either a standard profile provided by the
                               operator or a custom profile.  The "qos-profile" container defines
                               the traffic-scheduling policy to be used by the SP.</t>

                            <figure>
                              <artwork align="center">
                                <![CDATA[
                               Provider network
                          +-----------------------+
192.0.2.0/24
198.51.100.0/24 ---- CE --------- PE
                        \       /
                       qos-profile
                                ]]>
                              </artwork>
                            </figure>

                            <t>A custom QoS profile is defined as a list of classes of services and
                               associated properties.  The properties are:

                               <list style="symbols">

							      <t>direction: used to specify the direction to which 
								     the qos profile is applied.  This model supports three direction
                                     settings: "Site-to-WAN", "WAN-to-Site", and "both".  By default, 
									 the "both" direction value is used. In case of "both" direction, 
									 the provider should ensure scheduling according to the requested
									 policy in both traffic directions (SP to customer and customer to
									 SP). As an example, a device-scheduling policy may be implemented 
                                     on both the PE side and the CE side of the WAN link. In case of 
                                     "WAN-to-Site" direction, the provider should ensure scheduling from
									 the SP network to the customer site.  As an example, a device-
                                     scheduling policy may be implemented only on the PE side of the WAN
                                     link towards the customer.</t>
								  
                                  <t>rate-limit: used to rate-limit the class of service.  The value
                                     is expressed as a percentage of the global service bandwidth. 
									 When the qos-profile container is implemented on the CE side,
                                     svc-output-bandwidth is taken into account as a reference. When
                                     it is implemented on the PE side, svc-input-bandwidth is used.
									 </t>

                                  <t>latency: used to define the latency constraint of the class.  The
                                     latency constraint can be expressed as the lowest possible latency
                                     or a latency boundary expressed in milliseconds.  How this latency
                                     constraint will be fulfilled is up to the SP&apos;s implementation
									 of the service: a strict priority queuing may be used on the access
                                     and in the core network, and/or a low-latency routing configuration
									 may be created for this traffic class.</t>

                                  <t>jitter: used to define the jitter constraint of the class.  The
                                     jitter constraint can be expressed as the lowest possible jitter
                                     or a jitter boundary expressed in microseconds.  How this jitter
                                     constraint will be fulfilled is up to the SP&apos;s implementation
									 of the service: a strict priority queuing may be used on the access
                                     and in the core network, and/or a jitter-aware routing configuration
									 may be created for this traffic class.</t>

                                  <t>bandwidth: used to define a guaranteed amount of bandwidth for the
                                     class of service.  It is expressed as a percentage.  The
                                     "guaranteed-bw-percent" parameter uses available bandwidth as a
                                     reference.  When the qos-profile container is implemented on the
                                     CE side, svc-output-bandwidth is taken into account as a
                                     reference.  When it is implemented on the PE side,
                                     svc-input-bandwidth is used.  By default, the bandwidth
                                     reservation is only guaranteed at the access level.  The user can
                                     use the "end-to-end" leaf to request an end-to-end bandwidth
                                     reservation, including across the MPLS transport network.  (In
                                     other words, the SP will activate something in the MPLS core to
                                     ensure that the bandwidth request from the customer will be
                                     fulfilled by the MPLS core as well.)  How this is done (e.g., RSVP
                                     reservation, controller reservation) is out of scope for this
                                     document.</t>

                               </list></t>

                            <t>In addition, due to network conditions, some constraints may not be 
							   completely fulfilled by the SP; in this case, the SP should advise 
							   the customer about the limitations.  How this communication is done 
							   is out of scope for this document.</t>

                            <t>Example of service configuration using a standard QoS profile with 
							the following corresponding XML snippet:</t>

                            <figure>
                              <artwork align="center">
                                <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-profiles>
    <valid-provider-identifiers>
      <qos-profile-identifier>
        <id>GOLD</id>
      </qos-profile-identifier>
      <qos-profile-identifier>
        <id>PLATINUM</id>
      </qos-profile-identifier>
    </valid-provider-identifiers>
  </vpn-profiles>
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1245HRTFGJGJ154654</site-network-access-id>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <service>
            <svc-input-bandwidth>100000000</svc-input-bandwidth>
            <svc-output-bandwidth>100000000</svc-output-bandwidth>
            <svc-mtu>1514</svc-mtu>
            <qos>
              <qos-profile>
                <profile>PLATINUM</profile>
              </qos-profile>
            </qos>
          </service>
          <location-reference>L1</location-reference>
        </site-network-access>
        <site-network-access>
          <site-network-access-id>555555AAAA2344</site-network-access-id>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <service>
            <svc-input-bandwidth>2000000</svc-input-bandwidth>
            <svc-output-bandwidth>2000000</svc-output-bandwidth>
            <svc-mtu>1514</svc-mtu>
            <qos>
              <qos-profile>
                <profile>GOLD</profile>
              </qos-profile>
            </qos>
          </service>
        </site-network-access>
      </site-network-accesses>
    </site>
  </sites>
</l3vpn-svc>

                                ]]>
                              </artwork>
                            </figure>

                            <t>Example of service configuration using a custom QoS profile with
							the following corresponding XML snippet:</t>

                            <figure>
                              <artwork align="center">
                                <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-profiles>
    <valid-provider-identifiers>
      <qos-profile-identifier>
        <id>GOLD</id>
      </qos-profile-identifier>
      <qos-profile-identifier>
        <id>PLATINUM</id>
      </qos-profile-identifier>
    </valid-provider-identifiers>
  </vpn-profiles>
  <vpn-services>
    <vpn-service>
      <vpn-id>VPNA</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>SITE1</site-id>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>Site1</site-network-access-id>
          <location-reference>L1</location-reference>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <location-reference>L1</location-reference>
          <vpn-attachment>
            <vpn-id>VPNA</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
          <service>
            <svc-input-bandwidth>100000000</svc-input-bandwidth>
            <svc-output-bandwidth>100000000</svc-output-bandwidth>
            <qos>
              <qos-profile>
                <classes>
                  <class>
                    <class-id>REAL_TIME</class-id>
                    <rate-limit>10</rate-limit>
                    <latency>
                      <use-lowest-latency/>
                    </latency>
                    <bandwidth>
                      <guaranteed-bw-percent>80</guaranteed-bw-percent>
                    </bandwidth>
                  </class>
                  <class>
                    <class-id>DATA1</class-id>
                    <latency>
                      <latency-boundary>70</latency-boundary>
                    </latency>
                    <bandwidth>
                      <guaranteed-bw-percent>80</guaranteed-bw-percent>
                    </bandwidth>
                  </class>
                  <class>
                    <class-id>DATA2</class-id>
                    <latency>
                      <latency-boundary>200</latency-boundary>
                    </latency>
                    <bandwidth>
                      <guaranteed-bw-percent>5</guaranteed-bw-percent>
                      <end-to-end/>
                    </bandwidth>
                  </class>
                </classes>
              </qos-profile>
            </qos>
          </service>
        </site-network-access>
      </site-network-accesses>
    </site>
  </sites>
</l3vpn-svc>
                                ]]>
                              </artwork>
                            </figure>

                            <t>The custom QoS profile for Site1 defines a REAL_TIME class with a
                               latency constraint expressed as the lowest possible latency.  It also
                               defines two data classes -- DATA1 and DATA2.  The two classes express
                               a latency boundary constraint as well as a bandwidth reservation, as
                               the REAL_TIME class is rate-limited to 10% of the service bandwidth
                               (10% of 100 Mbps = 10 Mbps).  In cases where congestion occurs, the
                               REAL_TIME traffic can go up to 10 Mbps (let&apos;s assume that only 
							   5 Mbps are consumed).  DATA1 and DATA2 will share the remaining 
							   bandwidth (95 Mbps) according to their percentage.  So, the DATA1 
							   class will be served with at least 76 Mbps of bandwidth, while the 
							   DATA2 class will be served with at least 4.75 Mbps.  The latency 
							   boundary information of the data class may help the SP define a 
							   specific buffer tuning or a specific routing within the network.  
							   The maximum percentage to be used is not limited by this model but 
							   MUST be limited by the management system according to the policies 
							   authorized by the SP.</t>

                         </section>

                      </section>

                      <section anchor="multicast" title="Multicast">

                         <t>The "multicast" container defines the type of site in the customer
                            multicast service topology: source, receiver, or both.  These
                            parameters will help the management system optimize the multicast
                            service.  Users can also define the type of multicast relationship
                            with the customer: router (requires a protocol such as PIM), host
                            (IGMP or MLD), or both.  An address family (IPv4, IPv6, or both) can
                            also be defined.</t>

                      </section>

                   </section>

                   <section anchor="enhanced" title="Enhanced VPN Features">

                      <section anchor="carrycarry" title="Carriers&apos; Carriers">

                         <t>In the case of CsC <xref target="RFC4364" />, a customer may want to 
						    build an MPLS service using an IP VPN to carry its traffic.</t>

                         <figure>
                           <artwork align="center">
                             <![CDATA[
LAN customer1
    |
    |
   CE1
    |
    | -------------
 (vrf_cust1)
  CE1_ISP1
    |                 ISP1 POP
    | MPLS link
    | -------------
    |
 (vrf ISP1)
   PE1

  (...)               Provider backbone

   PE2
  (vrf ISP1)
    |
    | ------------
    |
    | MPLS link
    |                 ISP1 POP
   CE2_ISP1
   (vrf_cust1)
    | ------------
    |
   CE2
    |
 LAN customer1
                             ]]>
                           </artwork>
                         </figure>

                         <t>In the figure above, ISP1 resells an IP VPN service but has no core
                            network infrastructure between its POPs.  ISP1 uses an IP VPN as the
                            core network infrastructure (belonging to another provider) between
                            its POPs.</t>

                         <t>In order to support CsC, the VPN service must indicate MPLS support
                            by setting the "carrierscarrier" leaf to true in the vpn-service
                            list.  The link between CE1_ISP1/PE1 and CE2_ISP1/PE2 must also run
                            an MPLS signalling protocol.  This configuration is done at the site
                            level.</t>

                         <t>In the proposed model, LDP or BGP can be used as the MPLS signalling
                            protocol.  In the case of LDP, an IGP routing protocol MUST also be
                            activated.  In the case of BGP signalling, BGP MUST also be
                            configured as the routing protocol.</t>

                         <t>If CsC is enabled, the requested "svc-mtu" leaf will refer to the
                            MPLS MTU and not to the IP MTU. </t>

                      </section>

                   </section>

                   <section anchor="external" title="External ID References">

                      <t>The service model sometimes refers to external information through
                         identifiers.  As an example, to order a cloud-access to a particular
                         cloud service provider (CSP), the model uses an identifier to refer
                         to the targeted CSP.  If a customer is directly using this service
                         model as an API (through REST or NETCONF, for example) to order a
                         particular service, the SP should provide a list of authorized
                         identifiers.  In the case of cloud-access, the SP will provide the
                         associated identifiers for each available CSP.  The same applies to
                         other identifiers, such as std-qos-profile, OAM profile-name, and
                         provider-profile for encryption.</t>

                      <t>How an SP provides the meanings of those identifiers to the customer
                         is out of scope for this document.</t>

                   </section>

                   <section anchor="defnnis" title="Defining NNIs">

                      <t>An autonomous system (AS) is a single network or group of networks
                         that is controlled by a common system administration group and that
                         uses a single, clearly defined routing protocol.  In some cases, VPNs
                         need to span different ASes in different geographic areas or span
                         different SPs.  The connection between ASes is established by the SPs
                         and is seamless to the customer.  Examples include

                         <list style="symbols">

                            <t>a partnership between SPs (e.g., carrier, cloud) to extend their
                               VPN service seamlessly.</t>

                            <t>an internal administrative boundary within a single SP (e.g.,
                               backhaul versus core versus data center).</t>

                         </list></t>

                      <t>NNIs (network-to-network interfaces) have to be defined to extend the
                         VPNs across multiple ASes.</t>

                      <t><xref target="RFC4364" /> defines multiple flavors of VPN NNI 
					     implementations. Each implementation has pros and cons; this topic 
						 is outside the scope of this document.  For example, in an Inter-AS
						 option A, autonomous system border router (ASBR) peers are connected
						 by multiple interfaces with at least one of those interfaces spanning
						 the two ASes while being present in the same VPN.  In order for these
						 ASBRs to signal unlabeled IP prefixes, they associate each interface 
						 with a VPN routing and forwarding (VRF) instance and a Border Gateway
                         Protocol (BGP) session.  As a result, traffic between the
                         back-to-back VRFs is IP.  In this scenario, the VPNs are isolated
                         from each other, and because the traffic is IP, QoS mechanisms that
                         operate on IP traffic can be applied to achieve customer service
                         level agreements (SLAs).</t>

                      <figure>
                        <artwork align="center">
                          <![CDATA[
  --------                 --------------              -----------
 /        \               /              \            /           \
| Cloud    |             |                |          |             |
| Provider |-----NNI-----|                |----NNI---| Data Center |
|  #1      |             |                |          |             |
 \        /              |                |           \           /
  --------               |                |            -----------
                         |                |
  --------               |   My network   |           -----------
 /        \              |                |          /           \
| Cloud    |             |                |         |             |
| Provider |-----NNI-----|                |---NNI---|  L3VPN      |
|  #2      |             |                |         |  Partner    |
 \        /              |                |         |             |
  --------               |                |         |             |
                          \              /          |             |
                           --------------            \           /
                                 |                    -----------
                                 |
                                NNI
                                 |
                                 |
                         -------------------
                        /                   \
                       |                     |
                       |                     |
                       |                     |
                       |     L3VPN Partner   |
                       |                     |
                        \                   /
                         -------------------
                          ]]>
                        </artwork>
                      </figure>

                      <t>The figure above describes an SP network called "My network" that has
                         several NNIs.  This network uses NNIs to:

                         <list style="symbols">

                            <t>increase its footprint by relying on L3VPN partners.</t>

                            <t>connect its own data center services to the customer IP VPN.</t>

                            <t>enable the customer to access its private resources located in a
                               private cloud owned by some CSPs.</t>

                         </list></t>

                      <section anchor="opta" title="Defining an NNI with the Option A Flavor">

                         <figure>
                           <artwork align="center">
                             <![CDATA[
         AS A                                          AS B
  -------------------                         -------------------
 /                   \                       /                   \
|                     |                     |                     |
|                 ++++++++ Inter-AS link ++++++++                 |
|                 +      +_______________+      +                 |
|                 +  (VRF1)---(VPN1)----(VRF1)  +                 |
|                 + ASBR +               + ASBR +                 |
|                 +  (VRF2)---(VPN2)----(VRF2)  +                 |
|                 +      +_______________+      +                 |
|                 ++++++++               ++++++++                 |
|                     |                     |                     |
|                     |                     |                     |
|                     |                     |                     |
|                 ++++++++ Inter-AS link ++++++++                 |
|                 +      +_______________+      +                 |
|                 +  (VRF1)---(VPN1)----(VRF1)  +                 |
|                 + ASBR +               + ASBR +                 |
|                 +  (VRF2)---(VPN2)----(VRF2)  +                 |
|                 +      +_______________+      +                 |
|                 ++++++++               ++++++++                 |
|                     |                     |                     |
|                     |                     |                     |
 \                   /                       \                   /
  -------------------                         -------------------
                             ]]>
                           </artwork>
                         </figure>

                         <t>In option A, the two ASes are connected to each other with physical
                            links on ASBRs.  For resiliency purposes, there may be multiple
                            physical connections between the ASes.  A VPN connection -- physical
                            or logical (on top of physical) -- is created for each VPN that needs
                            to cross the AS boundary, thus providing a back-to-back VRF model.</t>

                         <t>From a service model&apos;s perspective, this VPN connection can be seen
                            as a site.  Let&apos;s say that AS B wants to extend some VPN connections
                            for VPN C on AS A.  The administrator of AS B can use this service
                            model to order a site on AS A.  All connection scenarios could be
                            realized using the features of the current model.  As an example, the
                            figure above shows two physical connections that have logical
                            connections per VPN overlaid on them.  This could be seen as a
                            dual-homed subVPN scenario.  Also, the administrator of AS B will be
                            able to choose the appropriate routing protocol (e.g., E-BGP) to
                            dynamically exchange routes between ASes.</t>

                         <t>This document assumes that the option A NNI flavor SHOULD reuse the
                            existing VPN site modeling.</t>

                         <t>Example: a customer wants its CSP A to attach its virtual network N
                            to an existing IP VPN (VPN1) that he has from L3VPN SP B.</t>

                         <figure>
                           <artwork align="center">
                             <![CDATA[
        CSP A                              L3VPN SP B

  -----------------                    -------------------
 /                 \                  /                   \
|       |           |                |                     |
|  VM --|       ++++++++  NNI    ++++++++                  |--- VPN1
|       |       +      +_________+      +                  |   Site#1
|       |--------(VRF1)---(VPN1)--(VRF1)+                  |
|       |       + ASBR +         + ASBR +                  |
|       |       +      +_________+      +                  |
|       |       ++++++++         ++++++++                  |
|  VM --|           |                |                     |--- VPN1
|       |Virtual    |                |                     |   Site#2
|       |Network    |                |                     |
|  VM --|           |                |                     |--- VPN1
|       |           |                |                     |   Site#3
 \                 /                  \                   /
  -----------------                    -------------------
                                               |
                                               |
                                             VPN1
                                            Site#4
                             ]]>
                           </artwork>
                         </figure>

                         <t>To create the VPN connectivity, the CSP or the customer may use the
                            L3VPN service model that SP B exposes.  We could consider that, as
                            the NNI is shared, the physical connection (bearer) between CSP A and
                            SP B already exists.  CSP A may request through a service model the
                            creation of a new site with a single site-network-access
                            (single-homing is used in the figure).  As a placement constraint,
                            CSP A may use the existing bearer reference it has from SP A to force
                            the placement of the VPN NNI on the existing link.  The XML snippet 
							below illustrates a possible configuration request to SP B:</t>

                         <figure>
                           <artwork align="center">
                             <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-profiles>
    <valid-provider-identifiers>
      <qos-profile-identifier>
        <id>GOLD</id>
      </qos-profile-identifier>
      <qos-profile-identifier>
        <id>PLATINUM</id>
      </qos-profile-identifier>
    </valid-provider-identifiers>
  </vpn-profiles>
  <vpn-services>
    <vpn-service>
      <vpn-id>VPN1</vpn-id>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>CSP_A_attachment</site-id>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <locations>
        <location>
          <location-id>1</location-id>
          <city>NY</city>
          <country-code>US</country-code>
        </location>
      </locations>
      <site-vpn-flavor>site-vpn-flavor-nni</site-vpn-flavor>
      <routing-protocols>
        <routing-protocol>
          <type>bgp</type>
          <bgp>
            <autonomous-system>500</autonomous-system>
            <address-family>ipv4</address-family>
          </bgp>
        </routing-protocol>
      </routing-protocols>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>CSP_A_VN1</site-network-access-id>
          <location-reference>L1</location-reference>
          <ip-connection>
            <ipv4>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <ip-connection>
            <ipv4>
              <address-allocation-type>
              static-address
              </address-allocation-type>
              <addresses>
                <provider-address>203.0.113.1</provider-address>
                <customer-address>203.0.113.2</customer-address>
                <mask>30</mask>
              </addresses>
            </ipv4>
          </ip-connection>
          <service>
            <svc-input-bandwidth>450000000</svc-input-bandwidth>
            <svc-output-bandwidth>450000000</svc-output-bandwidth>
            <svc-mtu>1514</svc-mtu>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <vpn-attachment>
            <vpn-id>VPN1</vpn-id>
            <site-role>any-to-any-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
      <management>
        <type>customer-managed</type>
      </management>
    </site>
  </sites>
</l3vpn-svc>
                             ]]>
                           </artwork>
                         </figure>

                         <t>The case described above is different from a scenario using the
                            cloud-accesses container, as the cloud-access provides a public cloud
                            access while this example enables access to private resources located
                            in a CSP network.</t>

                      </section>

                      <section anchor="optb" title="Defining an NNI with the Option B Flavor">

                         <figure>
                           <artwork align="center">
                             <![CDATA[
        AS A                                          AS B
  -------------------                         -------------------
 /                   \                       /                   \
|                     |                     |                     |
|                 ++++++++ Inter-AS link ++++++++                 |
|                 +      +_______________+      +                 |
|                 +      +               +      +                 |
|                 + ASBR +<---MP-BGP---->+ ASBR +                 |
|                 +      +               +      +                 |
|                 +      +_______________+      +                 |
|                 ++++++++               ++++++++                 |
|                     |                     |                     |
|                     |                     |                     |
|                     |                     |                     |
|                 ++++++++ Inter-AS link ++++++++                 |
|                 +      +_______________+      +                 |
|                 +      +               +      +                 |
|                 + ASBR +<---MP-BGP---->+ ASBR +                 |
|                 +      +               +      +                 |
|                 +      +_______________+      +                 |
|                 ++++++++               ++++++++                 |
|                     |                     |                     |
|                     |                     |                     |
 \                   /                       \                   /
  -------------------                         -------------------
                             ]]>
                           </artwork>
                         </figure>

                         <t>In option B, the two ASes are connected to each other with physical
                            links on ASBRs.  For resiliency purposes, there may be multiple
                            physical connections between the ASes.  The VPN "connection" between
                            ASes is done by exchanging VPN routes through MP-BGP 
							<xref target="RFC4760" />.</t>

                         <t>There are multiple flavors of implementations of such an NNI.  For
                            example:

                            <list style="numbers">

                               <t>The NNI is internal to the provider and is situated between a
                                   backbone and a data center.  There is enough trust between the
                                   domains to not filter the VPN routes.  So, all the VPN routes
								   are exchanged.  RT filtering may be implemented to save some
                                   unnecessary route states.</t>

                               <t>The NNI is used between providers that agreed to exchange VPN
                                   routes for specific RTs only.  Each provider is authorized to
								   use the RT values from the other provider.</t>

                               <t>The NNI is used between providers that agreed to exchange VPN
                                   routes for specific RTs only.  Each provider has its own RT
                                   scheme.  So, a customer spanning the two networks will have
                                   different RTs in each network for a particular VPN.</t>

                            </list></t>

                         <t>Case 1 does not require any service modeling, as the protocol enables
                            the dynamic exchange of necessary VPN routes.</t>

                         <t>Case 2 requires that an RT-filtering policy on ASBRs be maintained.
                            From a service modeling point of view, it is necessary to agree on
                            the list of RTs to authorize.</t>

                         <t>In Case 3, both ASes need to agree on the VPN RT to exchange, as well
                            as how to map a VPN RT from AS A to the corresponding RT in AS B (and
                            vice versa).</t>

                         <t>Those modelings are currently out of scope for this document.</t>

                         <figure>
                           <artwork align="center">
                             <![CDATA[
       CSP A                               L3VPN SP B

  -----------------                    ------------------
 /                 \                  /                  \
|       |           |                |                    |
|  VM --|       ++++++++   NNI    ++++++++                |--- VPN1
|       |       +      +__________+      +                |   Site#1
|       |-------+      +          +      +                |
|       |       + ASBR +<-MP-BGP->+ ASBR +                |
|       |       +      +__________+      +                |
|       |       ++++++++          ++++++++                |
|  VM --|           |                |                    |--- VPN1
|       |Virtual    |                |                    |   Site#2
|       |Network    |                |                    |
|  VM --|           |                |                    |--- VPN1
|       |           |                |                    |   Site#3
 \                 /                 |                    |
  -----------------                  |                    |
                                      \                  /
                                       ------------------
                                                |
                                                |
                                               VPN1
                                              Site#4
                             ]]>
                           </artwork>
                         </figure>

                         <t>The example above describes an NNI connection between CSP A and SP
                            network B.  Both SPs do not trust themselves and use a different RT
                            allocation policy.  So, in terms of implementation, the customer VPN
                            has a different RT in each network (RT A in CSP A and RT B in SP
                            network B).  In order to connect the customer virtual network in
                            CSP A to the customer IP VPN (VPN1) in SP network B, CSP A should
                            request that SP network B open the customer VPN on the NNI (accept
                            the appropriate RT).  Who does the RT translation depends on the
                            agreement between the two SPs: SP B may permit CSP A to request VPN
                            (RT) translation.</t>

                      </section>

                      <section anchor="optc" title="Defining an NNI with the Option C Flavor">

                         <figure>
                           <artwork align="center">
                             <![CDATA[
         AS A                                           AS B
  -------------------                          -------------------
 /                   \                        /                   \
|                     |                      |                     |
|                     |                      |                     |
|                     |                      |                     |
|                 ++++++++ Multihop E-BGP ++++++++                 |
|                 +      +                +      +                 |
|                 +      +                +      +                 |
|                 + RGW  +<----MP-BGP---->+ RGW  +                 |
|                 +      +                +      +                 |
|                 +      +                +      +                 |
|                 ++++++++                ++++++++                 |
|                     |                      |                     |
|                     |                      |                     |
|                     |                      |                     |
|                     |                      |                     |
|                     |                      |                     |
|                 ++++++++ Inter-AS link ++++++++                  |
|                 +      +_______________+      +                  |
|                 +      +               +      +                  |
|                 + ASBR +               + ASBR +                  |
|                 +      +               +      +                  |
|                 +      +_______________+      +                  |
|                 ++++++++               ++++++++                  |
|                     |                      |                     |
|                     |                      |                     |
|                     |                      |                     |
|                 ++++++++ Inter-AS link ++++++++                  |
|                 +      +_______________+      +                  |
|                 +      +               +      +                  |
|                 + ASBR +               + ASBR +                  |
|                 +      +               +      +                  |
|                 +      +_______________+      +                  |
|                 ++++++++               ++++++++                  |
|                     |                      |                     |
|                     |                      |                     |
 \                   /                        \                   /
  -------------------                          -------------------
                             ]]>
                           </artwork>
                         </figure>

                         <t>From a VPN service&apos;s perspective, the option C NNI is very 
						    similar to option B, as an MP-BGP session is used to exchange 
							VPN routes between the ASes.  The difference is that the 
							forwarding plane and the control plane are on different nodes, 
							so the MP-BGP session is multihop between routing gateway 
							(RGW) nodes.</t>

                         <t>From a VPN service&apos;s point of view, modeling options B 
						    and C will be identical.</t>

                      </section>

                   </section>

                </section>

                <section anchor="egsvcmod" title="Service Model Usage Example">

                   <t>As explained in <xref target="usage" />, this service model is 
				      intended to be instantiated at a management layer and is not 
					  intended to be used directly on network elements.  The management
					  system serves as a central point of configuration of the overall 
					  service.</t>

                   <t>This section provides an example of how a management system can use
                      this model to configure an IP VPN service on network elements.</t>

                   <t>In this example, we want to achieve the provisioning of a VPN 
				      service for three sites using a Hub-and-Spoke VPN service topology.
					  One of the sites will be dual-homed, and load-sharing is expected.</t>

                   <figure>
                     <artwork align="center">
                       <![CDATA[
+-------------------------------------------------------------+
|   Hub_Site  ------ PE1               PE2 ------ Spoke_Site1 |
|      |                   +----------------------------------+
|      |                   |
|      |                   +----------------------------------+
|   Hub_Site  ------ PE3               PE4 ------ Spoke_Site2 |
+-------------------------------------------------------------+
                       ]]>
                     </artwork>
                   </figure>

                   <t>The following XML snippet describes the overall simplified service
                      configuration of this VPN.</t>

                   <figure>
                     <artwork align="center">
                       <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-profiles>
    <valid-provider-identifiers>
      <qos-profile-identifier>
        <id>GOLD</id>
      </qos-profile-identifier>
      <qos-profile-identifier>
        <id>PLATINUM</id>
      </qos-profile-identifier>
    </valid-provider-identifiers>
  </vpn-profiles>
  <vpn-services>
    <vpn-service>
      <vpn-id>12456487</vpn-id>
      <vpn-service-topology>hub-spoke</vpn-service-topology>
    </vpn-service>
  </vpn-services>
</l3vpn-svc>
                       ]]>
                     </artwork>
                   </figure>

                   <t>When receiving the request for provisioning the VPN service, the
                      management system will internally (or through communication with
                      another OSS component) allocate VPN RTs.  In this specific case,
					  two RTs will be allocated (100:1 for Hub and 100:2 for Spoke).  
					  The output of corresponding XML snippet below describes the 
					  configuration of Spoke_Site1.</t>

                   <figure>
                     <artwork align="center">
                       <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-profiles>
    <valid-provider-identifiers>
      <qos-profile-identifier>
        <id>GOLD</id>
      </qos-profile-identifier>
      <qos-profile-identifier>
        <id>PLATINUM</id>
      </qos-profile-identifier>
    </valid-provider-identifiers>
  </vpn-profiles>
  <vpn-services>
    <vpn-service>
      <vpn-id>12456487</vpn-id>
      <vpn-service-topology>hub-spoke</vpn-service-topology>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>Spoke_Site1</site-id>
      <devices>
        <device>
          <device-id>D1</device-id>
        </device>
      </devices>
      <locations>
        <location>
          <location-id>1</location-id>
          <city>NY</city>
          <country-code>US</country-code>
        </location>
      </locations>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <routing-protocols>
        <routing-protocol>
          <type>bgp</type>
          <bgp>
            <autonomous-system>500</autonomous-system>
            <address-family>ipv4</address-family>
            <address-family>ipv6</address-family>
          </bgp>
        </routing-protocol>
      </routing-protocols>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>Spoke_Site1</site-network-access-id>
          <device-reference>D1</device-reference>
          <access-diversity>
            <groups>
              <group>
                <group-id>20</group-id>
              </group>
            </groups>
            <constraints>
              <constraint>
                <constraint-type>pe-diverse</constraint-type>
                <target>
                  <group>
                    <group-id>10</group-id>
                  </group>
                </target>
              </constraint>
            </constraints>
          </access-diversity>
          <ip-connection>
            <ipv4>
              <address-allocation-type>
             static-address
             </address-allocation-type>
              <addresses>
                <provider-address>203.0.113.254</provider-address>
                <customer-address>203.0.113.2</customer-address>
                <mask>24</mask>
              </addresses>
            </ipv4>
            <ipv6>
              <address-allocation-type>
             static-address
             </address-allocation-type>
              <addresses>
                <provider-address>2001:db8::1</provider-address>
                <customer-address>2001:db8::2</customer-address>
                <mask>64</mask>
              </addresses>
            </ipv6>
          </ip-connection>
          <service>
            <svc-input-bandwidth>450000000</svc-input-bandwidth>
            <svc-output-bandwidth>450000000</svc-output-bandwidth>
            <svc-mtu>1514</svc-mtu>
          </service>
          <security>
            <encryption>
              <layer>layer3</layer>
            </encryption>
          </security>
          <vpn-attachment>
            <vpn-id>12456487</vpn-id>
            <site-role>spoke-role</site-role>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
      <management>
        <type>provider-managed</type>
      </management>
    </site>
  </sites>
</l3vpn-svc>
                       ]]>
                     </artwork>
                   </figure>

                   <t>When receiving the request for provisioning Spoke_Site1, the
                      management system MUST allocate network resources for this site. It
                      MUST first determine the target network elements to provision the
                      access, particularly the PE router (and perhaps also an aggregation
                      switch).  As described in <xref target="deciding" />,  the management 
					  system SHOULD use the location information and MUST use the 
					  access-diversity constraint to find the appropriate PE. In this 
					  case, we consider that Spoke_Site1 requires PE diversity with the 
					  Hub and that the management system allocates PEs based on the least 
					  distance.  Based on the location information, the management system 
					  finds the available PEs in the area nearest the customer and picks 
					  one that fits the access-diversity constraint.</t>

                   <t>When the PE is chosen, the management system needs to allocate
                      interface resources on the node.  One interface is selected from the
                      pool of available PEs.  The management system can start provisioning
                      the chosen PE node via whatever means the management system prefers
                      (e.g., NETCONF, CLI).  The management system will check to see if a
                      VRF that fits its needs is already present.  If not, it will
                      provision the VRF: the RD will be derived from the internal
                      allocation policy model, and the RTs will be derived from the VPN
                      policy configuration of the site (the management system allocated
                      some RTs for the VPN).  As the site is a Spoke site (site-role), the
                      management system knows which RTs must be imported and exported.  As
                      the site is provider-managed, some management RTs may also be added
                      (100:5000).  Standard provider VPN policies MAY also be added in the
                      configuration.</t>

                   <t>Example of generated PE configuration:</t>

                   <figure>
                     <artwork align="center">
                       <![CDATA[
ip vrf Customer1
 export-map STD-CUSTOMER-EXPORT      <---- Standard SP configuration
 route-distinguisher 100:3123234324
 route-target import 100:1
 route-target import 100:5000        <---- Standard SP configuration
 route-target export 100:2                    for provider-managed CE
!
                       ]]>
                     </artwork>
                   </figure>

                   <t>When the VRF has been provisioned, the management system can start
                      configuring the access on the PE using the allocated interface
                      information.  IP addressing is chosen by the management system.  One
                      address will be picked from an allocated subnet for the PE, and
                      another will be used for the CE configuration.  Routing protocols
                      will also be configured between the PE and CE; because this model is
                      provider-managed, the choices are left to the SP.  BGP was chosen for
                      this example.  This choice is independent of the routing protocol
                      chosen by the customer.  BGP will be used to configure the CE-to-LAN
                      connection as requested in the service model.  Peering addresses will
                      be derived from those of the connection.  As the CE is provider-
                      managed, the CE&apos;s AS number can be automatically allocated by the
                      management system.  Standard configuration templates provided by the
                      SP may also be added.</t>

                   <t>Example of generated PE configuration:</t>

                   <figure>
                     <artwork align="center">
                       <![CDATA[
interface Ethernet1/1/0.10
 encapsulation dot1q 10
 ip vrf forwarding Customer1
 ip address 198.51.100.1 255.255.255.252 <---- Comes from
                                                automated allocation
 ipv6 address 2001:db8::10:1/64
 ip access-group STD-PROTECT-IN     <---- Standard SP config
!
router bgp 100
 address-family ipv4 vrf Customer1
  neighbor 198.51.100.2 remote-as 65000   <---- Comes from
                                                 automated allocation
  neighbor 198.51.100.2 route-map STD in  <---- Standard SP config
  neighbor 198.51.100.2 filter-list 10 in <---- Standard SP config
!
 address-family ipv6 vrf Customer1
  neighbor 2001:db8::0a10:2 remote-as 65000   <---- Comes from
                                                 automated allocation
  neighbor 2001:db8::0a10:2 route-map STD in  <---- Standard SP
                                                       config
  neighbor 2001:db8::0a10:2 filter-list 10 in <---- Standard SP
                                                       config
!
ip route vrf Customer1 192.0.2.1 255.255.255.255 198.51.100.2
! Static route for provider administration of CE
!
                       ]]>
                     </artwork>
                   </figure>

                   <t>As the CE router is not reachable at this stage, the management
                      system can produce a complete CE configuration that can be manually
                      uploaded to the node before sending the CE configuration to the
                      customer premises.  The CE configuration will be built in the same
                      way as the PE would be configured.  Based on the CE type
                      (vendor/model) allocated to the customer as well as the bearer
                      information, the management system knows which interface must be
                      configured on the CE.  PE-CE link configuration is expected to be
                      handled automatically using the SP OSS, as both resources are managed
                      internally.  CE-to-LAN-interface parameters such as IP addressing are
                      derived from the ip-connection container, taking into account how the
                      management system distributes addresses between the PE and CE within
                      the subnet.  This will allow a plug-and-play configuration for the CE
                      to be created.</t>

                   <t>Example of generated CE configuration:</t>

                   <figure>
                     <artwork align="center">
                       <![CDATA[
interface Loopback10
 description "Administration"
 ip address 192.0.2.1 255.255.255.255
!
interface FastEthernet10
 description "WAN"
 ip address 198.51.100.2 255.255.255.252 <---- Comes from
                                                automated allocation
 ipv6 address 2001:db8::0a10:2/64
!
interface FastEthernet11
 description "LAN"
 ip address 203.0.113.254 255.255.255.0 <---- Comes from the
                                            ip-connection container
 ipv6 address 2001:db8::1/64
!
router bgp 65000
 address-family ipv4
  redistribute static route-map STATIC2BGP <---- Standard SP
                                                    configuration
  neighbor 198.51.100.1 remote-as 100     <---- Comes from
                                              automated allocation
  neighbor 203.0.113.2 remote-as 500     <---- Comes from the
                                              ip-connection container
 address-family ipv6
  redistribute static route-map STATIC2BGP <---- Standard SP
                                                    configuration
  neighbor 2001:db8::0a10:1 remote-as 100     <---- Comes from
                                              automated allocation
  neighbor 2001:db8::2 remote-as 500     <---- Comes from the
                                              ip-connection container
!
route-map STATIC2BGP permit 10
 match tag 10
!
                       ]]>
                     </artwork>
                   </figure>

                </section>

                <section anchor="other" title="Interaction with Other YANG Modules">

                   <t>As expressed in <xref target="usage" />, this service model is 
				      intended to be instantiated in a management system and not 
					  directly on network elements.</t>

                   <t>The management system&apos;s role will be to configure the network
                      elements.  The management system may be modular, so the component
                      instantiating the service model (let&apos;s call it "service component")
                      and the component responsible for network element configuration
                      (let&apos;s call it "configuration component") may be different.</t>

                   <figure>
                     <artwork align="center">
                       <![CDATA[
          l3vpn-svc         |
            Model           |
                            |
                 +---------------------+
                 |  Service component  | Service datastore
                 +---------------------+
                            |
                            |
                 +---------------------+
            +----|  Config component   |------+
           /     +---------------------+       \   Network
          /            /            \           \  Configuration
         /            /              \           \ models
        /            /                \           \
++++++++         ++++++++           ++++++++       ++++++++
+ CE A + ------- + PE A +           + PE B + ----- + CE B + Config
++++++++         ++++++++           ++++++++       ++++++++ datastore

         Site A                              Site B
                       ]]>
                     </artwork>
                   </figure>

                   <t>In the previous sections, we provided some examples of the
                      translation of service provisioning requests to router configuration
                      lines.  In the NETCONF/YANG ecosystem, we expect NETCONF/YANG to be
                      used between the configuration component and network elements to
                      configure the requested services on those elements.</t>

                   <t>In this framework, specifications are expected to provide specific
                      YANG modeling of service components on network elements.  There will
                      be a strong relationship between the abstracted view provided by this
                      service model and the detailed configuration view that will be
                      provided by specific configuration models for network elements.</t>

                   <t>The authors of this document anticipate definitions of YANG models
                      for the network elements listed below.  Note that this list is not
                      exhaustive:

                      <list style="symbols">

                         <t>VRF definition, including VPN policy expression.</t>

                         <t>Physical interface.</t>

                         <t>IP layer (IPv4, IPv6).</t>

                         <t>QoS: classification, profiles, etc.</t>

                         <t>Routing protocols: support of configuration of all protocols
                            listed in the document, as well as routing policies associated
                            with those protocols.</t>

                         <t>Multicast VPN.</t>

                         <t>Network address translation.</t>

                      </list></t>

                   <t>Example of a corresponding XML snippet with a VPN site request at 
				      the service level, using this model:</t>

                   <figure>
                     <artwork align="center">
                       <![CDATA[
<?xml version="1.0"?>
<l3vpn-svc xmlns="urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc">
  <vpn-profiles>
    <valid-provider-identifiers>
      <qos-profile-identifier>
        <id>GOLD</id>
      </qos-profile-identifier>
      <qos-profile-identifier>
        <id>PLATINUM</id>
      </qos-profile-identifier>
    </valid-provider-identifiers>
  </vpn-profiles>
  <vpn-services>
    <vpn-service>
      <vpn-id>VPN1</vpn-id>
      <vpn-service-topology>hub-spoke</vpn-service-topology>
    </vpn-service>
  </vpn-services>
  <sites>
    <site>
      <site-id>Site A</site-id>
      <security>
        <encryption>
          <layer>layer3</layer>
        </encryption>
      </security>
      <locations>
        <location>
          <location-id>L1</location-id>
        </location>
      </locations>
      <site-network-accesses>
        <site-network-access>
          <site-network-access-id>1</site-network-access-id>
          <ip-connection>
            <ipv4>
              <address-allocation-type>
              static-address
              </address-allocation-type>
              <addresses>
                <provider-address>203.0.113.254</provider-address>
                <customer-address>203.0.113.2</customer-address>
                <mask>24</mask>
              </addresses>
            </ipv4>
            <ipv6>
              <address-allocation-type>provider-dhcp</address-allocation-type>
            </ipv6>
          </ip-connection>
          <service>
            <svc-mtu>1514</svc-mtu>
            <svc-input-bandwidth>10000000</svc-input-bandwidth>
            <svc-output-bandwidth>10000000</svc-output-bandwidth>
          </service>
          <location-reference>L1</location-reference>
          <vpn-attachment>
            <vpn-policy-id>VPNPOL1</vpn-policy-id>
          </vpn-attachment>
        </site-network-access>
      </site-network-accesses>
      <routing-protocols>
        <routing-protocol>
          <type>static</type>
          <static>
            <cascaded-lan-prefixes>
              <ipv4-lan-prefixes>
                <lan>198.51.100.0/30</lan>
                <next-hop>203.0.113.2</next-hop>
              </ipv4-lan-prefixes>
            </cascaded-lan-prefixes>
          </static>
        </routing-protocol>
      </routing-protocols>
      <management>
        <type>customer-managed</type>
      </management>
      <vpn-policies>
        <vpn-policy>
          <vpn-policy-id>VPNPOL1</vpn-policy-id>
          <entries>
            <id>1</id>
            <vpn>
              <vpn-id>VPN1</vpn-id>
              <site-role>any-to-any-role</site-role>
            </vpn>
          </entries>
        </vpn-policy>
      </vpn-policies>
    </site>
  </sites>
</l3vpn-svc>
                       ]]>
                     </artwork>
                   </figure>

                   <t>In the service example above, the service component is expected to
                      request that the configuration component of the management system
                      provide the configuration of the service elements.  If we consider
                      that the service component selected a PE (PE A) as the target PE for
                      the site, the configuration component will need to push the
                      configuration to PE A.  The configuration component will use several
                      YANG data models to define the configuration to be applied to PE A.
                      The XML snippet configuration of PE A might look like this:</t>

                    <figure>
                      <artwork align="center">
                        <![CDATA[
<if:interfaces>
     <if:interface>
      <if:name>eth0</if:name>
      <if:type>ianaift:ethernetCsmacd</if:type>
      <if:description>
       Link to CE A.
      </if:description>
      <ip:ipv4>
       <ip:address>
        <ip:ip>203.0.113.254</ip:ip>
        <ip:prefix-length>24</ip:prefix-length>
       </ip:address>
       <ip:forwarding>true</ip:forwarding>
      </ip:ipv4>
     </if:interface>
</if:interfaces>
<rt:routing>
    <rt:routing-instance>
      <rt:name>VRF_CustA</rt:name>
      <rt:type>l3vpn-network:vrf</rt:type>
      <rt:description>VRF for Customer A</rt:description>
      <l3vpn-network:route-distinguisher>
      100:1546542343
      </l3vpn-network:route-distinguisher>
      <l3vpn-network:import-rt>100:1</l3vpn-network:import-rt>
      <l3vpn-network:export-rt>100:1</l3vpn-network:export-rt>
      <rt:interfaces>
       <rt:interface>
        <rt:name>eth0</rt:name>
       </rt:interface>
      </rt:interfaces>
      <rt:routing-protocols>
       <rt:routing-protocol>
        <rt:type>rt:static</rt:type>
        <rt:name>st0</rt:name>
        <rt:static-routes>
         <v4ur:ipv4>
          <v4ur:route>
           <v4ur:destination-prefix>
           198.51.100.0/30
           </v4ur:destination-prefix>
           <v4ur:next-hop>
            <v4ur:next-hop-address>
            203.0.113.2
            </v4ur:next-hop-address>
           </v4ur:next-hop>
          </v4ur:route>
         </v4ur:ipv4>
        </rt:static-routes>
       </rt:routing-protocol>
      </rt:routing-protocols>
     </rt:routing-instance>
</rt:routing>
                        ]]>
                      </artwork>
                    </figure>

                 </section>

                 <section anchor="yang" title="YANG Module">

                    <figure>
                      <artwork align="center">
                        <![CDATA[
<CODE BEGINS>file "ietf-l3vpn-svc@2017-08-25.yang"
module ietf-l3vpn-svc {
 yang-version 1.1;
 namespace "urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc";
 prefix l3vpn-svc;
 import ietf-inet-types {
  prefix inet;
 }
 import ietf-yang-types {
  prefix yang;
 }
 import ietf-netconf-acm {
  prefix nacm;
 }
 organization
  "IETF L3SM Working Group";
 contact
  "WG List: <mailto:l3sm@ietf.org>
   Editor:
    L3SM WG

   Chairs:
    Adrian Farrel, Qin Wu
  ";

 description
  "This YANG module defines a generic service configuration
   model for Layer 3 VPNs. This model is common across all
   vendor implementations.";
 revision 2017-08-25 {
  description
   "First revision of RFC8049.";
  reference
   "RFC xxxx: YANG Data Model for L3VPN Service Delivery";
 }
 /* Features */
 feature cloud-access {
  description
   "Allows the VPN to connect to a CSP.";
 }
 feature multicast {
  description
   "Enables multicast capabilities in a VPN.";
 }
 feature ipv4 {
  description
   "Enables IPv4 support in a VPN.";
 }
 feature ipv6 {
  description
   "Enables IPv6 support in a VPN.";
 }
 feature lan-tag {
  description
   "Enables LAN Tag support in a VPN Policy Filter.";
 }
 feature carrierscarrier {
  description
   "Enables support of CsC.";
 }
 feature extranet-vpn {
  description
   "Enables support of extranet VPNs.";
 }
 feature site-diversity {
  description
   "Enables support of site diversity constraints.";
 }
 feature encryption {

  description
   "Enables support of encryption.";
 }
 feature qos {
  description
   "Enables support of classes of services.";
 }
 feature qos-custom {

  description
   "Enables support of the custom QoS profile.";
 }
 feature rtg-bgp {
  description
   "Enables support of the BGP routing protocol.";
 }
 feature rtg-rip {
  description
   "Enables support of the RIP routing protocol.";
 }
 feature rtg-ospf {
  description
   "Enables support of the OSPF routing protocol.";
 }
 feature rtg-ospf-sham-link {
  description
   "Enables support of OSPF sham links.";
 }
 feature rtg-vrrp {
  description
   "Enables support of the VRRP routing protocol.";
 }
 feature fast-reroute {
  description
   "Enables support of Fast Reroute.";
 }
 feature bfd {
  description
   "Enables support of BFD.";
 }
 feature always-on {
  description
   "Enables support of the 'always-on' access constraint.";
 }
 feature requested-type {
  description
   "Enables support of the 'requested-type' access constraint.";
 }

 feature bearer-reference {
  description
   "Enables support of the 'bearer-reference' access constraint.";
 }
 feature target-sites {
  description
   "Enables support of the 'target-sites' match flow parameter.";
 }
 /* Typedefs */

 typedef svc-id {
  type string;
  description
   "Defines a type of service component identifier.";
 }
 typedef template-id {
  type string;
  description
   "Defines a type of service template identifier.";
 }
 typedef address-family {
  type enumeration {
   enum ipv4 {
    description
     "IPv4 address family.";
   }
   enum ipv6 {
    description
     "IPv6 address family.";
   }
  }
  description
   "Defines a type for the address family.";
 }
 /* Identities */
 identity site-network-access-type {
  description
   "Base identity for site-network-access type.";
 }
 identity point-to-point {
  base site-network-access-type;
  description
   "Identity for point-to-point connection.";
 }
 identity multipoint {
  base site-network-access-type;
  description
   "Identity for multipoint connection.

    Example: Ethernet broadcast segment.";
 }
 identity placement-diversity {
  description
   "Base identity for site placement constraints.";
 }
 identity bearer-diverse {
  base placement-diversity;
  description
   "Identity for bearer diversity.

    The bearers should not use common elements.";
 }
 identity pe-diverse {
  base placement-diversity;
  description
   "Identity for PE diversity.";
 }
 identity pop-diverse {
  base placement-diversity;
  description
   "Identity for POP diversity.";
 }
 identity linecard-diverse {
  base placement-diversity;
  description
   "Identity for linecard diversity.";
 }
 identity same-pe {
  base placement-diversity;
  description
   "Identity for having sites connected on the same PE.";
 }
 identity same-bearer {
  base placement-diversity;
  description
   "Identity for having sites connected using the same bearer.";
 }
 identity customer-application {
  description
   "Base identity for customer application.";
 }
 identity web {
  base customer-application;
  description
   "Identity for Web application (e.g., HTTP, HTTPS).";
 }
 identity mail {

  base customer-application;
  description
   "Identity for mail application.";
 }
 identity file-transfer {
  base customer-application;
  description
   "Identity for file transfer application (e.g., FTP, SFTP).";
 }
 identity database {
  base customer-application;

  description
   "Identity for database application.";
 }
 identity social {
  base customer-application;
  description
   "Identity for social-network application.";
 }
 identity games {
  base customer-application;
  description
   "Identity for gaming application.";
 }
 identity p2p {
  base customer-application;
  description
   "Identity for peer-to-peer application.";
 }
 identity network-management {
  base customer-application;
  description
   "Identity for management application
    (e.g., Telnet, syslog, SNMP).";
 }
 identity voice {
  base customer-application;
  description
   "Identity for voice application.";
 }
 identity video {
  base customer-application;
  description
   "Identity for video conference application.";
 }
 identity site-vpn-flavor {
  description

   "Base identity for the site VPN service flavor.";
 }
 identity site-vpn-flavor-single {
  base site-vpn-flavor;
  description
   "Base identity for the site VPN service flavor.
    Used when the site belongs to only one VPN.";
 }
 identity site-vpn-flavor-multi {
  base site-vpn-flavor;
  description
   "Base identity for the site VPN service flavor.

    Used when a logical connection of a site
    belongs to multiple VPNs.";
 }
 identity site-vpn-flavor-sub {
  base site-vpn-flavor;
  description
   "Base identity for the site VPN service flavor.
    Used when a site has multiple logical connections.
    Each connection may belong to different multiple VPNs.";
 }
 identity site-vpn-flavor-nni {
  base site-vpn-flavor;
  description
   "Base identity for the site VPN service flavor.
    Used to describe an NNI option A connection.";
 }
 identity management {
  description
   "Base identity for site management scheme.";
 }
 identity co-managed {
  base management;
  description
   "Base identity for co-managed site.";
 }
 identity customer-managed {
  base management;
  description
   "Base identity for customer-managed site.";
 }
 identity provider-managed {
  base management;
  description
   "Base identity for provider-managed site.";
 }

 identity address-allocation-type {
  description
   "Base identity for address-allocation-type for PE-CE link.";
 }
 identity provider-dhcp {
  base address-allocation-type;
  description
   "Provider network provides DHCP service to customer.";
 }
 identity provider-dhcp-relay {
  base address-allocation-type;
  description
   "Provider network provides DHCP relay service to customer.";

 }
 identity provider-dhcp-slaac {
  base address-allocation-type;
  description
   "Provider network provides DHCP service to customer,
    as well as SLAAC.";
 }
 identity static-address {
  base address-allocation-type;
  description
   "Provider-to-customer addressing is static.";
 }
 identity slaac {
  base address-allocation-type;
  description
   "Use IPv6 SLAAC.";
 }
 identity site-role {
  description
   "Base identity for site type.";
 }
 identity any-to-any-role {
  base site-role;
  description
   "Site in an any-to-any IP VPN.";
 }
 identity spoke-role {
  base site-role;
  description
   "Spoke site in a Hub-and-Spoke IP VPN.";
 }
 identity hub-role {
  base site-role;
  description

   "Hub site in a Hub-and-Spoke IP VPN.";
 }
 identity vpn-topology {
  description
   "Base identity for VPN topology.";
 }
 identity any-to-any {
  base vpn-topology;
  description
   "Identity for any-to-any VPN topology.";
 }
 identity hub-spoke {
  base vpn-topology;
  description

   "Identity for Hub-and-Spoke VPN topology.";
 }
 identity hub-spoke-disjoint {
  base vpn-topology;
  description
   "Identity for Hub-and-Spoke VPN topology
    where Hubs cannot communicate with each other.";
 }
 identity multicast-tree-type {
  description
   "Base identity for multicast tree type.";
 }
 identity ssm-tree-type {
  base multicast-tree-type;
  description
   "Identity for SSM tree type.";
 }
 identity asm-tree-type {
  base multicast-tree-type;
  description
   "Identity for ASM tree type.";
 }
 identity bidir-tree-type {
  base multicast-tree-type;
  description
   "Identity for bidirectional tree type.";
 }
 identity multicast-rp-discovery-type {
  description
   "Base identity for RP discovery type.";
 }
 identity auto-rp {
  base multicast-rp-discovery-type;

  description
   "Base identity for Auto-RP discovery type.";
 }
 identity static-rp {
  base multicast-rp-discovery-type;
  description
   "Base identity for static type.";
 }
 identity bsr-rp {
  base multicast-rp-discovery-type;
  description
   "Base identity for BSR discovery type.";
 }
 identity routing-protocol-type {
  description

   "Base identity for routing protocol type.";
 }
 identity ospf {
  base routing-protocol-type;
  description
   "Identity for OSPF protocol type.";
 }
 identity bgp {
  base routing-protocol-type;
  description
   "Identity for BGP protocol type.";
 }
 identity static {
  base routing-protocol-type;
  description
   "Identity for static routing protocol type.";
 }
 identity rip {
  base routing-protocol-type;
  description
   "Identity for RIP protocol type.";
 }
 identity vrrp {
  base routing-protocol-type;
  description
   "Identity for VRRP protocol type.
    This is to be used when LANs are directly connected
    to PE routers.";
 }
 identity direct {
  base routing-protocol-type;
  description

   "Identity for direct protocol type.";
 }
 identity protocol-type {
  description
   "Base identity for protocol field type.";
 }
 identity tcp {
  base protocol-type;
  description
   "TCP protocol type.";
 }
 identity udp {
  base protocol-type;
  description
   "UDP protocol type.";
 }

 identity icmp {
  base protocol-type;
  description
   "ICMP protocol type.";
 }
 identity icmp6 {
  base protocol-type;
  description
   "ICMPv6 protocol type.";
 }
 identity gre {
  base protocol-type;
  description
   "GRE protocol type.";
 }
 identity ipip {
  base protocol-type;
  description
   "IP-in-IP protocol type.";
 }
 identity hop-by-hop {
  base protocol-type;
  description
   "Hop-by-Hop IPv6 header type.";
 }
 identity routing {
  base protocol-type;
  description
   "Routing IPv6 header type.";
 }
 identity esp {

  base protocol-type;
  description
   "ESP header type.";
 }
 identity ah {
  base protocol-type;
  description
   "AH header type.";
 }
 identity vpn-policy-filter-type {
  description
  "Base identity for VPN Policy filter type.";
 }
 identity ipv4 {
   base vpn-policy-filter-type;
   description
   "Identity for ipv4 prefix filter type.";

 }
 identity ipv6 {
   base vpn-policy-filter-type;
   description
   "Identity for ipv6 prefix filter type.";
}
 identity lan {
   base vpn-policy-filter-type;
   description
   "Identity for lan tag filter type.";
}

 identity qos-profile-direction {
  description
  "Base identity for qos profile direction.";
 }

  identity site-to-wan {
   base qos-profile-direction;
   description
   "Identity for Site to WAN direction.";

 }
   identity wan-to-site {
   base qos-profile-direction;
   description
   "Identity for WAN to Site direction.";

 }
   identity both {

   base qos-profile-direction;
   description
   "Identity for both WAN to Site direction and Site to WAN direction.";
 }
 /* Groupings */
 grouping vpn-service-cloud-access {
  container cloud-accesses {
   if-feature cloud-access;
   list cloud-access {
    key cloud-identifier;
    leaf cloud-identifier {
     type leafref {
      path "/l3vpn-svc/vpn-profiles/valid-provider-identifiers/"+
       "cloud-identifier/id";
     }
     description
      "Identification of cloud service.
       Local administration meaning.";
    }
    choice list-flavor {
     case permit-any {
      leaf permit-any {
       type empty;
       description
        "Allows all sites.";
      }
     }
      case deny-any-except {
      leaf-list permit-site {
       type leafref {
       path "/l3vpn-svc/sites/site/site-id";
      }
     description
     "Site ID to be authorized.";
      }
     }
     case permit-any-except {
     leaf-list deny-site {
      type leafref {
      path "/l3vpn-svc/sites/site/site-id";
     }
     description
     "Site ID to be denied.";
      }
     }
     description
      "Choice for cloud access policy.";
    }
    container address-translation {
     container nat44 {
      leaf enabled {
       type boolean;
       default false;
       description
        "Controls whether or not Network address
        translation from IPv4 to IPv4 (NAT44)
        [RFC3022]is required.";
      }
      leaf nat44-customer-address {
       type inet:ipv4-address;
       description
        "Address to be used for network address
        translation from IPv4 to IPv4. This is
        to be used if the customer is providing
        the IPv4 address. If customer address
                is not set, the model assumes that the
                provider will allocate the address.";
      }
      description
       "IPv4-to-IPv4 translation.";
     }
     description
      "Container for NAT.";

    }
    description
     "Cloud access configuration.";
   }
   description
    "Container for cloud access configurations.";
  }
  description
   "Grouping for VPN cloud definition.";
 }
 grouping multicast-rp-group-cfg {
  choice group-format {
   mandatory true;
   case singleaddress {
    leaf group-address {
     type inet:ip-address;

     description
      "A Single Multicast Group address.";
    }
   }
   case startend {
    leaf group-start {
     type inet:ip-address;
     description
      "The first Multicast group address in
       the multicast group address range.";
    }
    leaf group-end {
     type inet:ip-address;
     description
      "The last Multicast group address in
       the multicast group address range.";
    }
   }
   description
    "Choice for Multicast group format.";
  }
  description
   "This Grouping defines Multicast Group or
    Multicast Groups for RP-to-group mapping.";
 }
 grouping vpn-service-multicast {
  container multicast {
   if-feature multicast;
   leaf enabled {
    type boolean;
    default false;

    description
     "Enables multicast.";
   }
   container customer-tree-flavors {
    leaf-list tree-flavor {
     type identityref {
      base multicast-tree-type;
     }
     description
      "Type of tree to be used.";
    }
    description
     "Type of trees used by customer.";
   }
   container rp {
    container rp-group-mappings {
     list rp-group-mapping {

      key id;
      leaf id {
       type uint16;
       description
        "Unique identifier for the mapping.";
      }
      container provider-managed {
       leaf enabled {
        type boolean;
        default false;
        description
         "Set to true if the Rendezvous Point (RP)
         must be a provider-managed node. Set to false
         if it is a customer-managed node.";
       }
       leaf rp-redundancy {
        type boolean;
        default false;
        description
         "If true, a redundancy mechanism for the RP
          is required.";
       }
       leaf optimal-traffic-delivery {
        type boolean;
        default false;
        description
         "If true, the SP must ensure that
          traffic uses an optimal path, an SP may use
          Anycast RP or RP tree to SPT switchover
          architectures.";

       }
       description
        "Parameters for a provider-managed RP.";
      }
      leaf rp-address {
       when "../provider-managed/enabled = 'false'" {
        description
         "Relevant when the RP is not provider-managed.";
       }
       type inet:ip-address;
           mandatory true;
       description
        "Defines the address of the RP.
         Used if the RP is customer-managed.";
      }
      container groups {
       list group {
        key id;

        leaf id {
         type uint16;
         description
          "Identifier for the group.";
        }
        uses multicast-rp-group-cfg;
        description
         "List of Multicast groups.";
       }
       description
        "Multicast groups associated with the RP.";
      }
      description
       "List of RP to group mappings.";
     }
     description
      "RP to group mappings parameters.";
    }
    container rp-discovery {
     leaf rp-discovery-type {
      type identityref {
       base multicast-rp-discovery-type;
      }
      default static-rp;
      description
       "Type of RP discovery used.";
     }
     container bsr-candidates {
      when "derived-from-or-self(../rp-discovery-type, 'l3vpn-svc:bsr-rp')" {

       description
        "Only applicable if discovery type is BSR-RP.";
      }
      leaf-list bsr-candidate-address {
       type inet:ip-address;
       description
        "Address of BSR candidate.";
      }
      description
       "Container for List of Customer BSR candidate's addresses.";
     }
     description
      "RP discovery parameters.";
    }
    description
     "RP parameters.";
   }
   description
    "Multicast global parameters for the VPN service.";

  }
  description
   "Grouping for multicast VPN definition.";
 }
 grouping vpn-service-mpls {
  leaf carrierscarrier {
   if-feature carrierscarrier;
   type boolean;
   default false;
   description
    "The VPN is using CsC, and so MPLS is required.";
  }
  description
   "Grouping for MPLS CsC definition.";
 }
 grouping customer-location-info {
  container locations {
   list location {
    key location-id;
    leaf location-id {
     type svc-id;
     description
      "Identifier for a particular location.";
    }
    leaf address {
     type string;
     description
      "Address (number and street) of the site.";

    }
    leaf postal-code {
     type string;
     description
      "Postal code of the site.";
    }
    leaf state {
     type string;
     description
      "State of the site. This leaf can also be used to describe
       a region for a country that does not have states.";
    }
    leaf city {
     type string;
     description
      "City of the site.";
    }
    leaf country-code {
     type string {
      pattern '[A-Z]{2}';

     }
     description
      "Country of the site.
       Expressed as ISO ALPHA-2 code.";
    }
    description
     "Location of the site.";
   }
   description
    "List of locations for the site.";
  }
  description
   "This grouping defines customer location parameters.";
 }
 grouping site-group {
  container groups {
   list group {
    key group-id;
    leaf group-id {
     type string;
     description
      "Group-id the site belongs to.";
    }
    description
     "List of group-ids.";
   }
   description

    "Groups the site or site-network-access belongs to.";
  }
  description
   "Grouping definition to assign
    group-ids to site or site-network-access.";
 }
 grouping site-diversity {
  container site-diversity {
   if-feature site-diversity;
   uses site-group;
   description
    "Diversity constraint type.
     All site-network-accesses will inherit the group values
     defined here.";
  }
  description
   "This grouping defines site diversity parameters.";
 }
 grouping access-diversity {
  container access-diversity {
   if-feature site-diversity;

   uses site-group;
   container constraints {
    list constraint {
     key constraint-type;
     leaf constraint-type {
      type identityref {
       base placement-diversity;
      }
      description
       "Diversity constraint type.";
     }
     container target {
      choice target-flavor {
       default id;
       case id {
        list group {
         key group-id;
         leaf group-id {
          type string;
          description
           "The constraint will be applied against
            this particular group-id for this site network access level.";
         }
         description
          "List of group-ids associated with one specific
            constraint for this site network access level.";

        }
       }
       case all-accesses {
        leaf all-other-accesses {
         type empty;
         description
          "The constraint will be applied against
           all other site network accesses of this site.";
        }
       }
       case all-groups {
        leaf all-other-groups {
         type empty;
         description
          "The constraint will be applied against
           all other groups managed by the customer.";
        }
       }
       description
        "Choice for the target flavor definition.";
      }
      description

       "The constraint will be applied against
        Specific target, and the target can be a list
                of group-ids,all other site network accesses of
        this site or all other groups managed by the
        customer.";
     }
     description
      "List of constraints.";
    }
    description
     "Placement constraints for this site network access.";
   }
   description
    "Diversity parameters.";
  }
  description
   "This grouping defines access diversity parameters.";
 }
 grouping operational-requirements {
  leaf requested-site-start {
   type yang:date-and-time;
   description
    "Optional leaf indicating requested date and time when the
    service at a particular site is expected to start.";
  }

  leaf requested-site-stop {
   type yang:date-and-time;
   description
    "Optional leaf indicating requested date and time when the
    service at a particular site is expected to stop.";
  }
  description
   "This grouping defines some operational parameters.";
 }
 grouping operational-requirements-ops {
  leaf actual-site-start {
   type yang:date-and-time;
   config false;
   description
    "Optional leaf indicating actual date and time when the
    service at a particular site actually started.";
  }
  leaf actual-site-stop {
   type yang:date-and-time;
   config false;
   description
    "Optional leaf indicating actual date and time when the
    service at a particular site actually stopped.";

  }
  description
   "This grouping defines some operational parameters.";
 }
 grouping flow-definition {
  container match-flow {
   leaf dscp {
    type inet:dscp;
    description
     "DSCP value.";
   }
   leaf dot1p {
    type uint8 {
     range "0..7";
    }
    description
     "802.1p matching.";
   }
   leaf ipv4-src-prefix {
    type inet:ipv4-prefix;
    description
     "Match on IPv4 src address.";
   }
   leaf ipv6-src-prefix {

    type inet:ipv6-prefix;
    description
     "Match on IPv6 src address.";
   }
   leaf ipv4-dst-prefix {
    type inet:ipv4-prefix;
    description
     "Match on IPv4 dst address.";
   }
   leaf ipv6-dst-prefix {
    type inet:ipv6-prefix;
    description
     "Match on IPv6 dst address.";
   }
   leaf l4-src-port {
    type inet:port-number;
    description
     "Match on Layer 4 src port.";
   }
   leaf-list target-sites {
    if-feature target-sites;
    type svc-id;
    description
     "Identify a site as traffic destination.";

   }
   container l4-src-port-range {
    leaf lower-port {
     type inet:port-number;
     description
      "Lower boundary for port.";
    }
    leaf upper-port {
     type inet:port-number;
     must ". >= ../lower-port" {
      description
       "Upper boundary must be higher than lower boundary.";
     }
     description
      "Upper boundary for port.";
    }
    description
     "Match on Layer 4 src port range.";
   }
   leaf l4-dst-port {
    type inet:port-number;
    description
     "Match on Layer 4 dst port.";

   }
   container l4-dst-port-range {
    leaf lower-port {
     type inet:port-number;
     description
      "Lower boundary for port.";
    }
    leaf upper-port {
     type inet:port-number;
     must ". >= ../lower-port" {
      description
       "Upper boundary must be higher than lower boundary.";
     }
     description
      "Upper boundary for port.";
    }
    description
     "Match on Layer 4 dst port range.";
   }
   leaf protocol-field {
    type union {
     type uint8;
     type identityref {
      base protocol-type;
     }

    }
    description
     "Match on IPv4 protocol or IPv6 Next Header field.";
   }
   description
    "Describes flow-matching criteria.";
  }
  description
   "Flow definition based on criteria.";
 }
 grouping site-service-basic {
  leaf svc-input-bandwidth {
   type uint64;
   units bps;
   mandatory true;
   description
    "From the customer site's perspective, the service
        input bandwidth of the connection or download
        bandwidth from the SP to the site.";
  }
  leaf svc-output-bandwidth {
   type uint64;

   units bps;
   mandatory true;
   description
    "From the customer site's perspective, the service
        output bandwidth of the connection or upload
        bandwidth from the site to the SP.";
  }
  leaf svc-mtu {
   type uint16;
   units bytes;
   mandatory true;
   description
    "MTU at service level. If the service is IP,
     it refers to the IP MTU. If CsC is enabled,
     the requested 'svc-mtu' leaf will refer to the
     MPLS MTU and not to the IP MTU. ";
  }
  description
   "Defines basic service parameters for a site.";
 }
 grouping site-protection {
  container traffic-protection {
   if-feature fast-reroute;
   leaf enabled {
    type boolean;
    default false;

    description
     "Enables traffic protection of access link.";
   }
   description
    "Fast Reroute service parameters for the site.";
  }
  description
   "Defines protection service parameters for a site.";
 }
 grouping site-service-mpls {
  container carrierscarrier {
   if-feature carrierscarrier;
   leaf signalling-type {
    type enumeration {
     enum ldp {
      description
      "Use LDP as the signalling protocol
       between the PE and the CE. In this case,
       an IGP routing protocol must also be activated. ";
     }
     enum bgp {

      description
      "Use BGP (as per RFC 3107) as the signalling protocol
       between the PE and the CE.
       In this case, BGP must also be configured as
       the routing protocol.";
     }
    }
    default bgp;
    description
     "MPLS signalling type.";
   }
   description
    "This container is used when the customer provides
    MPLS-based services. This is only used in the case
    of CsC(i.e., a customer builds an MPLS service using
    an IP VPN to carry its traffic.";
  }
  description
   "Defines MPLS service parameters for a site.";
 }
 grouping site-service-qos-profile {
  container qos {
   if-feature qos;
   container qos-classification-policy {
    list rule {
     key id;
     ordered-by user;
     leaf id {
      type string;
      description
       "A description identifying qos classification
        policy rule.";
     }
     choice match-type {
      default match-flow;
      case match-flow {
       uses flow-definition;
      }
      case match-application {
       leaf match-application {
        type identityref {
         base customer-application;
        }
        description
         "Defines the application to match.";
       }
      }

      description
       "Choice for classification.";
     }
     leaf target-class-id {
      type string;
      description
       "Identification of the class of service.
       This identifier is internal to the administration.";
     }
     description
      "List of marking rules.";
    }
    description
     "Configuration of the traffic classification policy.";
   }
   container qos-profile {
    choice qos-profile {
     description
      "Choice for QoS profile.
       Can be standard profile or customized profile.";
     case standard {
      description "Standard QoS profile.";
      leaf profile {
       type leafref {
        path "/l3vpn-svc/vpn-profiles/valid-provider-identifiers/qos-profile-identifier/id";
       }
       description

        "QoS profile to be used.";
      }
     }
     case custom {
      description "Customized QoS profile.";
      container classes {
       if-feature qos-custom;
       list class {
        key class-id;
        leaf class-id {
         type string;
         description
          "Identification of the class of service.
           This identifier is internal to the administration.";
        }
                leaf direction {
                type identityref {
                  base qos-profile-direction;
                }

                default both;
                description
                "The direction which QoS profile is applied to";
                }

        leaf rate-limit {
         type uint8;
         units percent;
         description
          "To be used if the class must be rate-limited.
           Expressed as percentage of the service bandwidth.";
        }
        container latency {
         choice flavor {
          case lowest {
           leaf use-lowest-latency {
            type empty;
            description
             "The traffic class should use the path with the
              lowest latency.";
           }
          }
          case boundary {
           leaf latency-boundary {
            type uint16;
                        units msec;
            default 400;
            description
             "The traffic class should use a path with a
              defined maximum latency.";
           }
          }
          description
           "Latency constraint on the traffic class.";
         }
         description
          "Latency constraint on the traffic class.";
        }

        container jitter {
         choice flavor {
          case lowest {
           leaf use-lowest-jitter {
            type empty;
            description
             "The traffic class should use the path with the
              lowest jitter.";
           }

          }
          case boundary {
           leaf latency-boundary {
            type uint32;
            units usec;
            default 40000;
            description
             "The traffic class should use a path with a
              defined maximum jitter.";
           }
          }
          description
           "Jitter constraint on the traffic class.";
         }
         description
          "Jitter constraint on the traffic class.";
        }
        container bandwidth {
         leaf guaranteed-bw-percent {
          type uint8;
          units percent;
          mandatory true;
          description
           "To be used to define the guaranteed bandwidth
           as a percentage of the available service bandwidth.";
         }
         leaf end-to-end {
          type empty;
          description
           "Used if the bandwidth reservation
           must be done on the MPLS network too.";
         }
         description
          "Bandwidth constraint on the traffic class.";
        }
        description
         "List of classes of services.";
       }
       description
        "Container for list of classes of services.";
      }
     }
    }
    description
     "QoS profile configuration.";
   }
   description

    "QoS configuration.";
  }
  description
   "This grouping defines QoS parameters for a site.";
 }
 grouping site-security-authentication {
  container authentication {
   description
    "Authentication parameters.";
  }
  description
   "This grouping defines authentication parameters for a site.";
 }
 grouping site-security-encryption {
  container encryption {
   if-feature encryption;
   leaf enabled {
    type boolean;
    default false;
    description
     "If true, traffic encryption on the connection is required.";
   }
   leaf layer {
    type enumeration {
     enum layer2 {
      description
      "Encryption will occur at Layer 2.";
     }
     enum layer3 {
      description
      "Encryption will occur at Layer 3.
      For example, IPsec may be used when a customer requests Layer 3 encryption.";
     }
    }
    description
     "Layer on which encryption is applied.";
   }
   container encryption-profile {
    choice profile {
     case provider-profile {
      leaf profile-name {
       type leafref {
        path "/l3vpn-svc/vpn-profiles/valid-provider-identifiers/encryption-profile-identifier/id";
       }
       description
        "Name of the SP profile to be applied.";

      }
     }
     case customer-profile {
      leaf algorithm {
       type string;
       description
        "Encryption algorithm to be used.";
      }
      choice key-type {
       default psk;
       case psk {
        leaf preshared-key {
         type string;
         description
          " Pre-Shared Key(PSK) coming from customer.";
        }
       }
       description
        "Type of keys to be used.";
      }
     }
     description
      "Choice of encryption profile, the encryption
       profile can be provider profile or customer profile.";
    }
    description
     "Profile of encryption to be applied.";
   }
   description
    "Encryption parameters.";
  }
  description
   "This grouping defines encryption parameters for a site.";
 }
 grouping site-attachment-bearer {
  container bearer {
   container requested-type {
    if-feature requested-type;
    leaf requested-type {
     type string;

     description
      "Type of requested bearer: Ethernet, DSL,
      Wireless, etc. Operator specific.";
    }
    leaf strict {
     type boolean;
     default false;

     description
      "Defines whether requested-type is a preference
       or a strict requirement.";
    }
    description
     "Container for requested-type.";
   }
   leaf always-on {
    if-feature always-on;
    type boolean;
    default true;
    description
     "Request for an always-on access type.
     For example, this could mean no dial access type.";
   }
   leaf bearer-reference {
    if-feature bearer-reference;
    type string;
    description
     "This is an internal reference for the SP.";
   }
   description
    "Bearer-specific parameters.
    To be augmented.";
  }
  description
   "Defines physical properties of a site attachment.";
 }
 grouping site-routing {
  container routing-protocols {
   list routing-protocol {
    key type;
    leaf type {
     type identityref {
      base routing-protocol-type;
     }
     description
      "Type of routing protocol.";
    }
    container ospf {
     when "derived-from-or-self(../type, 'l3vpn-svc:ospf')" {

      description
       "Only applies when protocol is OSPF.";
     }
     if-feature rtg-ospf;
     leaf-list address-family {
      type address-family;

          min-elements "1";
      description
       "If OSPF is used on this site, this node
        contains configured value. This node
        contains at least one address family
        to be activated.";
     }
     leaf area-address {
      type yang:dotted-quad;
      mandatory true;
      description
       "Area address.";
     }
     leaf metric {
      type uint16;
      default 1;
      description
       "Metric of the PE-CE link. It is used
        in the routing state calculation and
        path selection. The default value is
        set to 1 assigned to the PE-CE link.";
     }
     container sham-links {
      if-feature rtg-ospf-sham-link;
      list sham-link {
       key target-site;
       leaf target-site {
        type svc-id;
        description
         "Target site for the sham link connection.
         The site is referred to by its ID.";
       }
       leaf metric {
        type uint16;
        default 1;
        description
         "Metric of the sham link. It is used in
          the routing state calculation and path
          selection. The default value is set
          to 1.";
       }
       description
        "Creates a sham link with another site.";
      }
      description
       "List of sham links.";
     }

     description
      "OSPF-specific configuration.";
    }
    container bgp {
     when "derived-from-or-self(../type, 'l3vpn-svc:bgp')" {
      description
       "Only applies when protocol is BGP.";
     }
     if-feature rtg-bgp;
     leaf autonomous-system {
      type uint32;
      mandatory true;
      description
       "Customer AS number in case the customer
           requests BGP routing.";
     }
     leaf-list address-family {
      type address-family;
          min-elements "1";
      description
       "If BGP is used on this site, this node
        contains configured value. This node
        contains at least one address family
        to be activated.";
     }
     description
      "BGP-specific configuration.";
    }
    container static {
     when "derived-from-or-self(../type, 'l3vpn-svc:static')" {
      description
       "Only applies when protocol is static.
        BGP activation requires the SP to know
        the address of the customer peer. When
        BGP is enabled, the 'static-address'
        allocation type for the IP connection
        MUST be used.";
     }
     container cascaded-lan-prefixes {
      list ipv4-lan-prefixes {
       if-feature ipv4;
       key "lan next-hop";
       leaf lan {

        type inet:ipv4-prefix;
        description
         "LAN prefixes.";
       }

       leaf lan-tag {
        type string;
        description
         "Internal tag to be used in VPN policies.";
       }
       leaf next-hop {
        type inet:ipv4-address;
        description
         "Next-hop address to use on the customer side.";
       }
       description
        "List of LAN prefixes for the site.";
      }
      list ipv6-lan-prefixes {
       if-feature ipv6;
       key "lan next-hop";
       leaf lan {
        type inet:ipv6-prefix;
        description
         "LAN prefixes.";
       }
       leaf lan-tag {
        type string;
        description
         "Internal tag to be used in VPN policies.";
       }
       leaf next-hop {
        type inet:ipv6-address;
        description
         "Next-hop address to use on the customer side.";
       }
       description
        "List of LAN prefixes for the site.";
      }
      description
       "LAN prefixes from the customer.";
     }
     description
      "Configuration specific to static routing.";
    }
    container rip {
     when "derived-from-or-self(../type, 'l3vpn-svc:rip')" {
      description
       "Only applies when protocol is RIP. For IPv4,

        the model assumes that RIP version 2 is used.";
     }
     if-feature rtg-rip;

     leaf-list address-family {
      type address-family;
          min-elements "1";
      description
       "If RIP is used on this site, this node
        contains configured value.This node
        contains at least one address family
        to be activated.";
     }
     description
      "Configuration specific to RIP routing.";
    }
    container vrrp {
     when "derived-from-or-self(../type, 'l3vpn-svc:vrrp')" {
      description
       "Only applies when protocol is VRRP.";
     }
     if-feature rtg-vrrp;
     leaf-list address-family {
      type address-family;
          min-elements "1";
      description
       "If VRRP is used on this site, this node
        contains configured value. This node contains
        at least one address family to be activated. ";
     }
     description
      "Configuration specific to VRRP routing.";
    }
    description
     "List of routing protocols used on
   the site. This list can be augmented.";
   }
   description
    "Defines routing protocols.";
  }
  description
   "Grouping for routing protocols.";
 }
 grouping site-attachment-ip-connection {
  container ip-connection {
   container ipv4 {
    if-feature ipv4;
    leaf address-allocation-type {
     type identityref {
      base address-allocation-type;
     }
     must "current() != 'slaac' and current() != 'provider-dhcp-slaac'" {
      error-message "SLAAC is only applicable to IPv6";
     }
     description
      "Defines how addresses are allocated. 
	  If there is no value for address 
	  allocation type, then the ipv4 is not enabled.";
    }
 container provider-dhcp {
  when "derived-from-or-self(../address-allocation-type, 'l3vpn-svc:provider-dhcp')" {
  description
  "Only applies when addresses are allocated by DHCP.";
 }
     leaf provider-address {
      type inet:ipv4-address;
      description
      "Address of provider side";
     }
     leaf mask {
      type uint8 {
      range "0..31";
      }
      description
       "Subnet mask expressed in bits. The value zero
        means unspecified (by the customer)";
     }
     choice address-assign {
      default number;
      case number {
       leaf number-of-dynamic-address {
        type uint8;
        default 1;
        description
         "Describes the number of IP addresses the customer requires.";
       }
      }
      case explicit {
       container customer-addresses {
        list address-group {
         key "group-id";
         leaf group-id {
         type string;
         description
         "Group-id the list of start-to-end address belongs to.";
         }
        leaf start-address {
         type inet:ipv4-address;
          description
          "First address.";
         }

        leaf end-address {
         type inet:ipv4-address;
          description
          "Last address.";
         }
          description
          "Describes IP addresses allocated by DHCP.";
        }
         description
         "Container for customer addresses allocated by DHCP.";
       }
     }
         description
         "Choice for the way to assign addresses.";
     }
         description
         "DHCP allocated addresses related parameters.";
    }

 container dhcp-relay {
 when "derived-from-or-self(../address-allocation-type, 'l3vpn-svc:provider-dhcp-relay')" {
  description
  "Only applies when provider is required to implement
  DHCP relay function.";
  }
 leaf provider-address {
  type inet:ipv4-address;
  description
   "Address of provider side";
 }
 leaf mask {
  type uint8 {
  range "0..31";
  }
 description
  "Subnet mask expressed in bits. The value zero
  means unspecified (by the customer)";
 }
 container customer-dhcp-servers {
  leaf-list server-ip-address {
  type inet:ipv4-address;
  description
  "IP address of customer DHCP server.";
 }
 description
  "Container for list of customer DHCP servers.";
 }
 description
 "DHCP relay provided by operator.";
}

 container addresses {
  when "derived-from-or-self(../address-allocation-type, 'l3vpn-svc:static-address')" {
  description
  "Only applies when protocol allocation type is static.";
  }
     leaf provider-address {
      type inet:ipv4-address;
      description
       "IPv4 Address List of provider side. When protocol
        allocation type is static, provider address must be configured.";
     }
     leaf customer-address {
      type inet:ipv4-address;
      description
       "IPv4 Address of customer side.";
     }
     leaf mask {
      type uint8 {
       range "0..31";
      }
      description
       "Subnet mask expressed in bits. ";
     }
     description
      "Describes IPv4 addresses used.";
    }
    description
     "IPv4-specific parameters.";
   }
   container ipv6 {
    if-feature ipv6;
    leaf address-allocation-type {
     type identityref {
      base address-allocation-type;
     }
     description
      "Defines how addresses are allocated.
	   If there is no value for address 
	   allocation type, then the ipv6 is 
	   not enabled.";
    }

   container provider-dhcp {
        when "../address-allocation-type = 'l3vpn-svc:provider-dhcp' "+
        "or ../address-allocation-type "+"= 'l3vpn-svc:provider-dhcp-slaac'" {

         description
         "Only applies when addresses are allocated by DHCP.";
        }
        leaf provider-address {
         type inet:ipv6-address;
         description
          "Address of provider side";
        }
        leaf mask {
         type uint8 {
          range "0..127";
         }
         description
          "Subnet mask expressed in bits. The value zero
           means unspecified (by the customer)";
        }
        choice address-assign {
         default number;
         case number {
          leaf number-of-dynamic-address {
           type uint8;
           default 1;
           description
            "Describes the number of IP addresses the customer requires.";
          }
         }
         case explicit {
          container customer-addresses {
           list address-group {
                key "group-id";
                leaf group-id {
                 type string;
                 description
                  "Group-id the list of start-to-end address belongs to.";
                }
                leaf start-address {
                 type inet:ipv6-address;
                 description
                  "First address.";
                }

                leaf end-address {
                 type inet:ipv6-address;
                 description
                  "Last address.";
                }
                description
                 "Describes IP addresses allocated by DHCP.";

          }
          description
          "Container for customer addresses allocated by DHCP.";
         }
        }
         description
         "Choice for the way to assign addresses.";
        }
         description
         "DHCP allocated addresses related parameters.";
        }
  container dhcp-relay {
  when "derived-from-or-self(../address-allocation-type, 'l3vpn-svc:provider-dhcp-relay')" {
   description
   "Only applies when provider is required to implement
    DHCP relay function.";
     }
        leaf provider-address {
         type inet:ipv6-address;
         description
          "Address of provider side";
        }
        leaf mask {
         type uint8 {
          range "0..127";
         }
         description
          "Subnet mask expressed in bits. The value zero
           means unspecified (by the customer)";
        }

     container customer-dhcp-servers {
      leaf-list server-ip-address {
       type inet:ipv6-address;
       description
        "This node contains IP address of
        customer DHCP server.If DHCP relay
        function is implemented by the
        provider, this node contains the

        configured value.";
      }
      description
       "Container for list of customer DHCP servers.";
     }
     description
      "DHCP relay provided by operator.";
    }

    container addresses {
     when "derived-from-or-self(../address-allocation-type, 'l3vpn-svc:static-address')" {
      description
       "Only applies when protocol allocation type is static.";
     }
     leaf provider-address {
      type inet:ipv6-address;
      description
       "IPv6 Address of provider side. When protocol
        allocation type is static, provider address must be configured.";
     }
     leaf customer-address {
      type inet:ipv6-address;
      description
       "IPv6 Address of customer side.";
     }
     leaf mask {
      type uint8 {
       range "0..127";
      }
      description
       "Subnet mask expressed in bits.";
     }
     description
      "Describes IPv6 addresses used.";
    }
    description
     "IPv6-specific parameters.";
   }
   container oam {
    container bfd {
     if-feature bfd;
     leaf enabled {
      type boolean;
      default false;
      description
       "If true, BFD activation is required.";
     }
     choice holdtime {
      default fixed;
      case fixed {
       leaf fixed-value {
        type uint32;
        units msec;
        description
         "Expected BFD holdtime expressed in msec. The customer

          may impose Some fixed values for the holdtime period if the
          provider allows the customer use this function.";
       }
      }
      case profile {
       leaf profile-name {
        type leafref {
         path "/l3vpn-svc/vpn-profiles/valid-provider-identifiers/bfd-profile-identifier/id";
        }
        description
         "Well-known SP profile Name. The provider can propose some profiles
          to the customer, depending on the service level the customer wants
          to achieve. Profile names must be communicated to the customer";
       }
       description
        "Well-known SP profile.";
      }
      description
       "Choice for holdtime flavor.";
     }
     description
      "Container for BFD.";
    }
    description
     "Defines the OAM mechanisms used on the connection.
      BFD is set as a fault detection mechanism, but the 'oam' container
      can easily be augmented by other mechanisms";
   }
   description
    "Defines connection parameters.";
  }
  description
   "This grouping defines IP connection parameters.";
 }
 grouping site-service-multicast {
  container multicast {
   if-feature multicast;
   leaf multicast-site-type {
    type enumeration {

     enum receiver-only {
      description
       "The site only has receivers.";
     }
     enum source-only {
      description
       "The site only has sources.";
     }

     enum source-receiver {
      description
       "The site has both sources and receivers.";
     }
    }
    default source-receiver;
    description
     "Type of multicast site.";
   }
   container multicast-address-family {
    leaf ipv4 {
     if-feature ipv4;
     type boolean;
     default false;
     description
      "Enables IPv4 multicast.";
    }
    leaf ipv6 {
     if-feature ipv6;
     type boolean;
     default false;
     description
      "Enables IPv6 multicast.";
    }
    description
     "Defines protocol to carry multicast.";
   }
   leaf protocol-type {
    type enumeration {
     enum host {
      description
      "Hosts are directly connected to the provider network.
       Host protocols such as IGMP or MLD are required.";
     }
     enum router {
      description
      "Hosts are behind a customer router.
       PIM will be implemented.";
     }
     enum both {
      description
      "Some hosts are behind a customer router, and some others
       are directly connected to the provider network.
       Both host and routing protocols must be used.
       Typically, IGMP and PIM will be implemented.";
     }
    }
    default "both";

    description
     "Multicast protocol type to be used with the customer site.";
   }
   description
    "Multicast parameters for the site.";
  }
  description
   "Multicast parameters for the site.";
 }
 grouping site-management {
  container management {
   leaf type {
    type identityref {
     base management;
    }
    mandatory true;
    description
     "Management type of the connection.";
   }
   description
    "Management configuration.";
  }
  description
   "Management parameters for the site.";
 }
 grouping site-devices {
  container devices {
   when "derived-from-or-self(../management/type, 'l3vpn-svc:provider-managed') or "+
    "derived-from-or-self(../management/type, 'l3vpn-svc:co-managed')" {
    description
     "Applicable only for provider-managed or co-managed device.";
   }
   list device {
    key device-id;
    leaf device-id {
     type svc-id;
     description
      "Identifier for the device.";
    }
    leaf location {

     type leafref {
      path "../../../locations/"+
       "location/location-id";
     }
     mandatory true;
     description
      "Location of the device.";

    }
    container management {
     when "derived-from-or-self(../../../management/type,"+
      "'l3vpn-svc:co-managed')" {
      description
       "Applicable only for co-managed device.";
     }
     leaf address-family {
      type address-family;
      description
       "Address family used for management.";
     }
     leaf address {
      type inet:ip-address;
      description
       "Management address.";
     }
     description
      "Management configuration. Applicable only for
       co-managed device.";
    }
    description
     "Device configuration.";
   }
   description
    "List of devices requested by customer.";
  }
  description
   "Grouping for device allocation.";
 }
 grouping site-vpn-flavor {
  leaf site-vpn-flavor {
   type identityref {
    base site-vpn-flavor;
   }
   default site-vpn-flavor-single;
   description
    "Defines the way the VPN multiplexing is done ,e.g.,whether
    the site belongs to a single VPN site or a multiVPN; In case
    of multiVPN, whether the logical accesses of the sites belong
    to the same set of VPNs or each logical accesses map to

    different VPNs. ";
  }
  description
   "Grouping for site VPN flavor.";
 }
 grouping site-vpn-policy {

  container vpn-policies {
   list vpn-policy {
    key vpn-policy-id;
    leaf vpn-policy-id {
     type svc-id;
     description
      "Unique identifier for the VPN policy.";
    }
    list entries {
     key id;
     leaf id {
      type svc-id;
      description
       "Unique identifier for the policy entry.";
     }
     container filters {
      list filter {
       key type;
       ordered-by user;
       leaf type {
        type identityref {
         base vpn-policy-filter-type;
         }
        description
         "Type of VPN Policy filter.";
        }
		leaf-list lan-tag {
		 when "derived-from-or-self(../type, 'l3vpn-svc:lan')" {
         description
          "Only applies when VPN Policy filter is LAN Tag filter.";
        }
		 if-feature lan-tag;
         type string;
         description
          "List of 'lan-tag' items to be matched. Lan-tag
           is Internal tag to be used in VPN policies ";
        }
        leaf-list ipv4-lan-prefix {
	     when "derived-from-or-self(../type, 'l3vpn-svc:ipv4')" {
          description
         "Only applies when VPN Policy filter is IPv4 Prefix filter.";
         }
		 if-feature ipv4;
         type inet:ipv4-prefix;
         description
          "List of IPv4 prefixes as LAN Prefixes to be matched.";
        }
        leaf-list ipv6-lan-prefix {
		 when "derived-from-or-self(../type, 'l3vpn-svc:ipv6')" {
         description
          "Only applies when VPN Policy filter is IPv6 Prefix filter.";
         }
		 if-feature ipv6;
         type inet:ipv6-prefix;
         description
          "List of IPv6 prefixes as LAN prefixes to be matched.";
        }
         description
        "List of filters used on the site. This list can
         be augmented.";
      }
      description
       "If a more-granular VPN attachment is necessary, filtering can
        be used. If used, it permits the splitting of site LANs among
        multiple VPNs.The Site LAN can be split based on either LAN-tag
        or LAN prefix. If no filter is used, all the LANs will be
        part of the same VPNs with the same role.";
     }
     list vpn {
          key vpn-id;
      leaf vpn-id {
       type leafref {
        path "/l3vpn-svc/vpn-services/"+
         "vpn-service/vpn-id";
       }
       mandatory true;
       description
        "Reference to an IP VPN.";
      }
      leaf site-role {
       type identityref {
        base site-role;
       }
       default any-to-any-role;
       description
        "Role of the site in the IP VPN.";
      }
      description
       "List of VPNs the LAN is associated with.";
     }
     description
      "List of entries for export policy.";
    }
    description
     "List of VPN policies.";
   }
   description
    "VPN policy.";
  }
  description
   "VPN policy parameters for the site.";
 }
 grouping site-maximum-routes {

  container maximum-routes {
   list address-family {

    key af;
    leaf af {
     type address-family;
     description
      "Address family.";
    }
    leaf maximum-routes {
     type uint32;
     description
      "Maximum prefixes the VRF can accept for this address family.";
    }
    description
     "List of address families.";
   }
   description
    "Defines 'maximum-routes' for the VRF.";
  }
  description
   "Defines 'maximum-routes' for the site.";
 }
 grouping site-security {
  container security {
   uses site-security-authentication;
   uses site-security-encryption;
   description
    "Site-specific security parameters.";
  }
  description
   "Grouping for security parameters.";
 }
 grouping site-service {
  container service {
   uses site-service-qos-profile;
   uses site-service-mpls;
   uses site-service-multicast;
   description
    "Service parameters on the attachment.";
  }
  description
   "Grouping for service parameters.";
 }
 grouping site-network-access-service {
  container service {
   uses site-service-basic;
   uses site-service-qos-profile;
   uses site-service-mpls;
   uses site-service-multicast;
   description

    "Service parameters on the attachment.";
  }
  description
   "Grouping for service parameters.";
 }
 grouping vpn-extranet {
  container extranet-vpns {
   if-feature extranet-vpn;
   list extranet-vpn {
    key vpn-id;
    leaf vpn-id {
     type svc-id;
     description
      "Identifies the target VPN the local VPN want to access.";
    }
    leaf local-sites-role {
     type identityref {
      base site-role;
     }
     default any-to-any-role;
     description
      "This describes the role of the
       local sites in the target VPN topology. In the any-to-any VPN
       service topology, the local sites must have the same role, which
       will be 'any-to-any-role '.In the Hub-and-Spoke VPN service
       topology or the Hub and Spoke disjoint VPN service topology,
       the local sites must have a Hub role or a Spoke role.";
    }
    description
     "List of extranet VPNs or target VPNs the local VPN is attached to.";
   }
   description
    "Container for extranet VPN configuration.";
  }
  description
   "Grouping for extranet VPN configuration.
    This provides an easy way to interconnect
    all sites from two VPNs.";
 }
 grouping site-attachment-availability {
  container availability {
   leaf access-priority {
    type uint32;
    default 100;
    description
     "Defines the priority for the access.

      The higher the access-priority value,

      the higher the preference of the
      access will be.";
   }
   description
    "Availability parameters (used for multihoming).";
  }
  description
   "Defines availability parameters for a site.";
 }
 grouping access-vpn-policy {
  container vpn-attachment {
   choice attachment-flavor {
    case vpn-policy-id {
     leaf vpn-policy-id {
      type leafref {
       path "../../../../"+
        "vpn-policies/vpn-policy/"+
        "vpn-policy-id";
      }
      description
       "Reference to a VPN policy. When referencing VPN
        policy for attachment, the vpn-policy-id must be
        configured.";
     }
    }
    case vpn-id {
     leaf vpn-id {
      type leafref {
       path "/l3vpn-svc/vpn-services"+
        "/vpn-service/vpn-id";
      }
      description
       "Reference to a IP VPN. Referencing a vpn-id provides
        an easy way to attach a particular logical access to
        a VPN. In this case, vpn-id must be configured.";
     }
     leaf site-role {
      type identityref {
       base site-role;
      }
      default any-to-any-role;
      description
       "Role of the site in the IP VPN. When referencing a vpn-id,
        the site-role setting must be added to express the role of
        the site in the target VPN service topology.";
     }
    }

    mandatory true;
    description
     "Choice for VPN attachment flavor. A choice is implemented
      to allow the user to choose the flavor that provides the
      best fit.";
   }
   description
    "Defines VPN attachment of a site.";
  }
  description
   "Defines the VPN attachment rules for
   a site's logical access.";
 }
 grouping vpn-profile-cfg {
  container valid-provider-identifiers {
   list cloud-identifier {
    if-feature cloud-access;
    key id;
    leaf id {
     type string;
     description
      "Identification of cloud service.
       Local administration meaning.";
    }
    description
    "List for Cloud Identifiers.";
   }
   list encryption-profile-identifier {
    key id;
    leaf id {
     type string;
     description
      "Identification of the SP encryption profile
       to be used. Local administration meaning.";
    }
    description
    "List for encryption profile identifiers.";
   }
   list qos-profile-identifier {
    key id;
    leaf id {
     type string;
     description
      "Identification of the QoS Profile to be used.
       Local administration meaning.";
    }
    description
    "List for QoS Profile Identifiers.";

   }

   list bfd-profile-identifier {
    key id;
    leaf id {
     type string;
     description
      "Identification of the SP BFD Profile to be used.
       Local administration meaning.";
    }
    description
    "List for BFD profile Identifiers.";
   }
     nacm:default-deny-write;
     description
    "Container for Valid Provider Identifies.";
  }
   description
   "Grouping for VPN Profile configuration.";
 }
 grouping vpn-svc-cfg {
  leaf vpn-id {
   type svc-id;
   description
    "VPN identifier. Local administration meaning.";
  }
  leaf customer-name {
   type string;
   description
    "Name of the customer which actually uses vpn service.
     In the case that any intermediary (e.g. Tier-2 provider
     or partner) sells the vpn service to their enduser
     on behalf of the original service provider (e.g. Tier-1
     provider), the original service provider may require the
     customer name to provide smooth activation/commitioning
     and operation for the service.";
  }
  leaf vpn-service-topology {
   type identityref {
    base vpn-topology;
   }
   default any-to-any;
   description
    "VPN service topology.";
  }
  uses vpn-service-cloud-access;
  uses vpn-service-multicast;
  uses vpn-service-mpls;

  uses vpn-extranet;
  description

   "Grouping for VPN service configuration.";
 }
 grouping site-top-level-cfg {
  uses operational-requirements;
  uses customer-location-info;
  uses site-devices;
  uses site-diversity;
  uses site-management;
  uses site-vpn-policy;
  uses site-vpn-flavor;
  uses site-maximum-routes;
  uses site-security;
  uses site-service;
  uses site-protection;
  uses site-routing;
  description
   "Grouping for site top-level configuration.";
 }
 grouping site-network-access-top-level-cfg {
  leaf site-network-access-type {
   type identityref {
    base site-network-access-type;
   }
   default point-to-point;
   description
    "Describes the type of connection, e.g.,
     point-to-point or multipoint.";
  }
  choice location-flavor {
   case location {
    when "derived-from-or-self(../../management/type, "+
     "'l3vpn-svc:customer-managed')" {
     description
      "Applicable only for customer-managed device.";
    }
    leaf location-reference {
     type leafref {
      path "../../../locations/location/location-id";
     }
     description
      "Location of the site-network-access.";
    }
   }
   case device {
    when "derived-from-or-self(../../management/type, "+

     "'l3vpn-svc:provider-managed') or "+
     "derived-from-or-self(../../management/type, "+
     "'l3vpn-svc:co-managed')" {

     description
      "Applicable only for provider-managed or co-managed device.";
    }
    leaf device-reference {
     type leafref {
      path "../../../devices/device/device-id";
     }
     description
      "Identifier of CE to use.";
    }
   }
   mandatory true;
   description
    "Choice of how to describe the site's location.";
  }
  uses access-diversity;
  uses site-attachment-bearer;
  uses site-attachment-ip-connection;
  uses site-security;
  uses site-network-access-service;
  uses site-routing;
  uses site-attachment-availability;
  uses access-vpn-policy;
  description
   "Grouping for site network access top-level configuration.";
 }
 /* Main blocks */
 container l3vpn-svc {
  container vpn-profiles {
   uses vpn-profile-cfg;
    description
    "Container for VPN Profiles.";
  }
  container vpn-services {
   list vpn-service {
    key vpn-id;
    uses vpn-svc-cfg;
    description
     "List of VPN services.";
   }
   description
    "Top-level container for the VPN services.";
  }
  container sites {

   list site {
    key site-id;
    leaf site-id {
     type svc-id;

     description
      "Identifier of the site.";
    }
    uses site-top-level-cfg;
    uses operational-requirements-ops;
    container site-network-accesses {
     list site-network-access {
      key site-network-access-id;
      leaf site-network-access-id {
       type svc-id;
       description
        "Identifier for the access.";
      }
      uses site-network-access-top-level-cfg;
      description
       "List of accesses for a site.";
     }
     description
      "List of accesses for a site.";
    }
    description
     "List of sites.";
   }
   description
    "Container for sites.";
  }
  description
   "Main container for L3VPN service configuration.";
 }
}
<CODE ENDS>
                        ]]>
                      </artwork>
                    </figure>

                 </section>

                 <section anchor="security" title="Security Considerations">

                    <t>The YANG module defined in this document MAY be accessed via the
                       RESTCONF protocol <xref target="RFC8040" /> or the NETCONF protocol
					   <xref target="RFC6241" />.  The lowest RESTCONF or NETCONF layer 
					   requires that the transport-layer protocol provide both data integrity
					   and confidentiality; see Section 2 in <xref target="RFC8040"/> and 
					   Section 2 in <xref target="RFC6241" />.  The client MUST carefully 
					   examine the certificate presented by the server to determine if it meets
					   the client&apos;s expectations, and the server MUST authenticate client 
					   access to any protected resource.  The client identity derived from the 
					   authentication mechanism used is subject to the NETCONF Access Control 
					   Model (NACM) <xref target="RFC6536" />.  Other protocols that are used 
					   to access this YANG module are also required to support similar security
					   mechanisms.</t>

                    <t>The data nodes defined in the "ietf-l3vpn-svc" YANG module MUST be
                       carefully created, read, updated, or deleted as appropriate.  The
                       entries in the lists below include customer-proprietary or
                       confidential information; therefore, access to confidential
                       information MUST be limited to authorized clients, and other clients
                       MUST NOT be permitted to access the information.

                       <list style="symbols">

                          <t>/l3vpn-svc/vpn-services/vpn-service</t>

                          <t>/l3vpn-svc/sites/site</t>

                       </list></t>

                    <t>The data model defines some security parameters than can be extended
                       via augmentation as part of the customer service request; those
                       parameters are described in <xref target="sec" />.</t>

                 </section>

                 <section anchor="iana" title="IANA Considerations">

                    <t>IANA has assigned a new URI from the "IETF XML Registry" 
					   <xref target="RFC3688" />.</t>

                    <figure>
                      <artwork align="center">
                        <![CDATA[
URI: urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc
Registrant Contact: The IESG
XML: N/A; the requested URI is an XML namespace.
                        ]]>
                      </artwork>
                    </figure>

                    <t>IANA has recorded a YANG module name in the "YANG Module Names"
                       registry <xref target="RFC7950" /> as follows:</t>

                    <figure>
                      <artwork align="center">
                        <![CDATA[
Name: ietf-l3vpn-svc
Namespace: urn:ietf:params:xml:ns:yang:ietf-l3vpn-svc
Prefix: l3vpn-svc
Reference: RFC 8049
                        ]]>
                      </artwork>
                    </figure>
                    <t>IANA is requested to update this registry to reference this
                     document on publication as an RFC.</t>
                 </section>

  </middle>

  <back>

    <references title="Normative References">
      <?rfc include="reference.RFC.2119"?>
      <?rfc include="reference.RFC.3688"?>
      <?rfc include="reference.RFC.4364"?>
      <?rfc include="reference.RFC.4577"?>
      <?rfc include="reference.RFC.4862"?>
      <?rfc include="reference.RFC.6241"?>
      <?rfc include="reference.RFC.6513"?>
      <?rfc include="reference.RFC.6536"?>
      <?rfc include="reference.RFC.7950"?>
      <?rfc include="reference.RFC.8040"?>
      <?rfc include="reference.RFC.8049"?>
    </references>

    <references title="Informative References">
	  <?rfc include="reference.RFC.4026"?>
      <?rfc include="reference.RFC.4110"?>
      <?rfc include="reference.RFC.4760"?>
    </references>

    <section title="Acknowledgements">

       <t>Maxim Klyus, Luis Miguel Contreras, 
	      Gregory Mirsky, Zitao Wang, Jing Zhao, Kireeti Kompella, Eric Rosen, 
		  Aijun Wang,Michael Scharf, Xufeng Liu, David Ball, Lucy Yong, Jean-Philippe
          Landry, and Andrew Leu provided useful review to this document.</t>
		  
	   <t>Jan Lindblad reviewed the first release of RFC8049 and found some bugs
		  and His thorough YANG Doctor review on the YANG Model is valuable input to 
		  revision of RFC8049. David ball also provided a second review on published 
		  RFC8049.</t>
		
	   <t>Many thanks to these people. </t>

    </section>

    <section title="Contributors">

       <t>The authors would like to thank Rob Shakir for his major
          contributions to the initial modeling and use cases.</t>

       <t>Adrian Farrel prepared the editorial revisions for this bis.</t>

    </section>

  </back>

</rfc>