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Operations & Management NETCONF Draft This document provides a NETCONF binding to subscribed notifications and to YANG push. RFC Editor note: please replace the four references to pre-RFC normative drafts with the actual assigned RFC numbers.

This document provides a binding for events streamed over the NETCONF protocol as per . In addition, as is itself built upon , this document enables a NETCONF client to request and receive updates from a YANG datastore located on a NETCONF server.

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 RFC 2119. The following terms are defined in : notification message, stream, publisher, receiver, subscriber, subscription, configured subscription.

To support multiple subscriptions on a single session, a NETCONF publisher MUST support the :interleave capability as defined in . Such support MUST be indicated by the following capability: "urn:ietf:params:netconf:capability:interleave:1.0". Advertisement of both the :interleave capability and "urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications" within a NETCONF capability exchange MUST indicate that a NETCONF publisher is able to receive, process, and respond to NETCONF requests and subscription operations.

A publisher is allowed to concurrently support both and 's "create-subscription" RPC, however this support MUST NOT happen on a single transport NETCONF session. To accomplish this: A solution must reply with the error "operation-not-supported" if a "create-subscription" RPC is received on a NETCONF session where at least one subscription is currently active. It is a prohibited to send updates or state change notifications for a configured subscription on a NETCONF session where the create-subscription RPC has successfully created a subscription. A "create-subscription" RPC MUST be rejected if a subscription is already active across that NETCONF transport session.

A NETCONF publisher MUST support XML encoding of RPCs and Notifications. A NETCONF publisher supporting MUST support the "NETCONF" event stream identified in that draft. A NETCONF publisher supporting MUST support the operational state datastore as defined by .

For dynamic subscriptions, if the NETCONF session involved with the "establish-subscription" terminates, the subscription MUST be deleted.

For a configured subscription, there is no guarantee a transport session is currently in place with each associated receiver. In cases where a configured subscription has a receiver in the connecting state and the protocol configured as NETCONF, but no NETCONF transport session exists to that receiver, the publisher MUST initiate a transport session via NETCONF call home , section 4.1 to that receiver. Until NETCONF connectivity is established and a subscription-started state change notification is successfully sent, that receiver MUST remain in a status of either "connecting" or "timeout". If the call home fails because the publisher receives receiver credentials which are subsequently declined per , Section 4.1, step S5 authentication, then that receiver MUST be assigned a "timeout" status. If the call home fails to establish for any other reason, the publisher MUST NOT progress the receiver to the "active" state. Additionally, the publisher SHOULD place the receiver into a "timeout" status after a predetermined number of either failed call home attempts or NETCONF sessions remotely terminated by the receiver. NETCONF Transport session connectivity SHOULD be verified via Section 4.1, step S7. If an active NETCONF session is disconnected but the stop-time of a subscription has not been reached, the publisher MUST restart the call home process and return the receiver to the "connecting" state.

Notification messages transported over NETCONF will be identical in format and content to those encoded using one-way operations defined within , section 4.

Management of dynamic subscriptions occurs via RPCs as defined in and . When an RPC error occurs, the NETCONF RPC reply MUST include an "rpc-error" element per with the error information populated as follows: "error-type" of "application". "error-tag" of "operation-failed". Optionally, an "error-severity" of "error" (this MAY but does not have to be included). "error-app-tag" with the value being a string that corresponds to an identity associated with the error, as defined in section 2.4.6 for general subscriptions, and Appendix A.1, for datastore (YANG-Push) subscriptions. The tag to use depends on the RPC for which the error occurred. Applicable are identities with a base identity of "establish-subscription-error" (for error responses to an establish-subscription request), "modify- subscription-error" (for error responses to a modify-subscription request), "delete-subscription-error" (for error responses to a delete-subscription request), "resynch-subscription-error" (for error responses to resynch-subscription request), or "kill- subscription-error" (for error responses to a kill-subscription request), respectively. In case of error responses to an establish-subscription or modify- subscription request: optionally, "error-info" containing XML- encoded data with hints regarding parameter settings that might lead to successful requests in the future, per yang-data definitions "establish-subscription-error-datastore" (for error responses to an establish-subscription request) or "modify- subscription-error-datastore (for error responses to a modify- subscription request), respectively. These yang-data that is included in "error-info" SHOULD NOT include the optional leaf "error-reason", as such a leaf would be redundant with the information that is already placed within the error-app-tag. In case of an rpc error as a result of a delete-subscription, or a kill-subscription, or a resynch-subscription request, no error-info needs to be included, as the subscription-id is the only RPC input parameter and no hints regarding RPC input parameters need to be provided. Note that "error-path" does not need to be included with the "rpc-error" element, as subscription errors are generally not associated with nodes in the datastore but with the choice of RPC input parameters.

Notification messages (including state change notifications) are never sent before the NETCONF capabilities exchange has completed. If a malicious or buggy NETCONF subscriber sends a number of "establish-subscription" requests, then these subscriptions accumulate and may use up system resources. In such a situation, subscriptions MAY be terminated by terminating the underlying NETCONF session. The publisher MAY also suspend or terminate a subset of the active subscriptions on that NETCONF session. The NETCONF Authorization Control Model SHOULD be used to control and restrict authorization of subscription configuration.

We wish to acknowledge the helpful contributions, comments, and suggestions that were received from: Andy Bierman, Yan Gang, Sharon Chisholm, Hector Trevino, Peipei Guo, Susan Hares, Tim Jenkins, Balazs Lengyel, Martin Bjorklund, Mahesh Jethanandani, Kent Watsen, and Guangying Zheng.

As defined in an event stream exposes a continuous set of events available for subscription. A NETCONF client can retrieve the list of available event streams from a NETCONF publisher using the "get" operation against the top-level container "/streams" defined in . The following example illustrates the retrieval of the list of available event streams using the "get" operation.

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After such a request, the NETCONF publisher returns a list of event streams available.

The following figure shows two successful "establish-subscription" RPC requests as per . The first request is given a subscription identifier of 22, the second, an identifier of 23.

| | | | | | establish-subscription | |----------------------------->| (a) | RPC Reply: OK, id = 22 | |<-----------------------------| (b) | | | notification message (for 22)| |<-----------------------------| | | | | | establish-subscription | |----------------------------->| | RPC Reply: OK, id = 23 | |<-----------------------------| | | | | | notification message (for 22)| |<-----------------------------| | notification message (for 23)| |<-----------------------------| | | ]]>

To provide examples of the information being transported, example messages for interactions (a) and (b) in are detailed below:

NETCONF /ex:foo 10 ]]>

As NETCONF publisher was able to fully satisfy the request (a), the publisher sends the subscription identifier of the accepted subscription within message (b):

22 ]]>

If the NETCONF publisher had not been able to fully satisfy the request, or subscriber has no authorization to establish the subscription, the publisher would have sent an RPC error response. For instance, if the "dscp" value of 10 asserted by the subscriber in proved unacceptable, the publisher may have returned:

application operation-failed error dscp-unavailable 100 ]]>

The subscriber can use this information in future attempts to establish a subscription.

An existing subscription may be modified. The following exchange shows a negotiation of such a modification via several exchanges between a subscriber and a publisher. This negotiation consists of a failed RPC modification request/response, followed by a successful one.

| (c) | RPC error (with hint) | |<-----------------------------| (d) | | | modify-subscription (id = 23)| |----------------------------->| | RPC Reply: OK | |<-----------------------------| | | | notification message (for 23)| |<-----------------------------| | | ]]>

If the subscription being modified in is a datastore subscription as per , the modification request made in (c) may look like that shown in . As can be seen, the modifications being attempted are the application of a new xpath filter as well as the setting of a new periodic time interval.

/interfaces-state/interface/oper-status 500 23 ]]>

If the NETCONF publisher can satisfy both changes, the publisher sends a positive result for the RPC. If the NETCONF publisher cannot satisfy either of the proposed changes, the publisher sends an RPC error response (d). The following is an example RPC error response for (d) which includes a hint. This hint is an alternative time period value which might have resulted in a successful modification:

application operation-failed error period-unsupported 3000 ]]>

The following demonstrates deleting a subscription.

22 ]]>

If the NETCONF publisher can satisfy the request, the publisher replies with success to the RPC request. If the NETCONF publisher cannot satisfy the request, the publisher sends an error-rpc element indicating the modification didn't work. shows a valid response for existing valid subscription identifier, but that subscription identifier was created on a different NETCONF transport session:

application operation-failed error no-such-subscription ]]>

Configured subscriptions may be established, modified, and deleted using configuration operations against the top-level subtree of or . In this section, we present examples of how to manage the configuration subscriptions using a NETCONF client.

For subscription creation, a NETCONF client may send:

22 encode-xml NETCONF

1.2.3.4

1234 ]]>

If the request is accepted, the publisher will indicate this. If the request is not accepted because the publisher cannot serve it, no configuration is changed. In this case the publisher may reply:

application resource-denied error Temporarily the publisher cannot serve this subscription due to the current workload. ]]>

After a subscription has been created, NETCONF connectivity to each receiver's IP address and port will be established if it does not already exist. This will be accomplished via . The following figure shows the interaction model for the successful creation of a configured subscription.

| | | | | | | | | Edit-config | | |--------------------------->| | | RPC Reply: OK | | |<---------------------------| | | | Call Home | | |<-------------->| | | | | | subscription- | | | started | | |--------------->| | | | | | notification | | | message | | |--------------->| ]]>

Configured subscriptions can be modified using configuration operations against the top-level container "/subscriptions". For example, the subscription established in the previous section could be modified as follows, here a adding a second receiver:

1922

1.2.3.5

1234 ]]>

If the request is accepted, the publisher will indicate success. The result is that the interaction model described in may be extended as follows.

| | | Edit-config | | | |--------------------------->| | | | RPC Reply: OK | | | |<---------------------------| | | | | subscription- | | | | started | | | |---------------------------->| | | | | | | notification | | | | message | | | |--------------->| | | |---------------------------->| | | | | ]]>

Note in the above that in the specific example above, modifying a configured subscription actually resulted in "subscription-started" notification. And because of an existing NETCONF session, no additional call home was needed. Also note that if the edit of the configuration had impacted the filter, a separate modify-subscription would have been required for the original receiver.

Configured subscriptions can be deleted using configuration operations against the top-level container "/subscriptions". Deleting the subscription above would result in the following flow impacting all active receivers.

| | | |---------------------------->| | | | | | Edit-config | | | |--------------------------->| | | | RPC Reply: OK | | | |<---------------------------| | | | | subscription- | | | | terminated | | | |--------------->| | | |---------------------------->| | | | | ]]>

A publisher will send subscription state notifications according to the definitions within ).

A "subscription-started" over NETCONF encoded in XML would look like:

2007-09-01T10:00:00Z 39 encode-xml NETCONF /ex:foo ]]>

The "subscription-modified" is identical to , with just the word "started" being replaced by "modified".

A "subscription-completed" would look like:

2007-09-01T10:00:00Z 39 ]]>

The "subscription-resumed" and "replay-complete" are virtually identical, with "subscription-completed" simply being replaced by "subscription-resumed" and "replay-complete" in both encodings.

A "subscription-terminated" would look like:

2007-09-01T10:00:00Z 39 suspension-timeout ]]>

The "subscription-suspended" is virtually identical, with "subscription-terminated" simply being replaced by "subscription-suspended".

(To be removed by RFC editor prior to publication)

Tweaks and clarification on :interleave.

XML encoding and operational datastore mandatory. Error mechanisms and examples updated.

Moved examples to appendices All examples rewritten based on namespace learnings Normative text consolidated in front Removed all mention of JSON Call home process detailed Note: this is a major revision attempting to cover those comments received from two week review.

Added additional detail to "configured subscriptions" Added interleave capability Adjusted terminology to that in draft-ietf-netconf-subscribed-notifications Corrected namespaces in examples

Text simplifications throughout v02 had no meaningful changes

Added Call Home in solution for configured subscriptions. Clarified support for multiple subscription on a single session. No need to support multiple create-subscription. Added mapping between terminology in yang-push and (the one followed in this document). Editorial improvements.