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Versions: (draft-gonzalez-netconf-event-notifications) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 RFC 8640

NETCONF                                                          E. Voit
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                                A. Clemm
Expires: November 16, 2019                                        Huawei
                                                      A. Gonzalez Prieto
                                                               Microsoft
                                                       E. Nilsen-Nygaard
                                                             A. Tripathy
                                                           Cisco Systems
                                                            May 15, 2019


    Dynamic subscription to YANG Events and Datastores over NETCONF
           draft-ietf-netconf-netconf-event-notifications-21

Abstract

   This document provides a Network Configuration Protocol (NETCONF)
   binding to the dynamic subscription capability of both subscribed
   notifications and YANG-Push.

   RFC Editor note: please replace the references to pre-RFC normative
   drafts with the actual assigned RFC numbers.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 16, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents



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   (https://trustee.ietf.org/license-info) in effect on the date of
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   than English.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Compatibility with RFC-5277's create-subscription . . . . . .   3
   4.  Mandatory XML, event stream and datastore support . . . . . .   4
   5.  NETCONF connectivity and the Dynamic Subscriptions  . . . . .   4
   6.  Notification Messages . . . . . . . . . . . . . . . . . . . .   4
   7.  Dynamic Subscriptions and RPC Error Responses . . . . . . . .   5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   7
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     11.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .   8
     A.1.  Event Stream Discovery  . . . . . . . . . . . . . . . . .   8
     A.2.  Dynamic Subscriptions . . . . . . . . . . . . . . . . . .   9
     A.3.  Subscription State Notifications  . . . . . . . . . . . .  14
     A.4.  Filter Examples . . . . . . . . . . . . . . . . . . . . .  15
   Appendix B.  Changes between revisions  . . . . . . . . . . . . .  17
     B.1.  v20 to v21  . . . . . . . . . . . . . . . . . . . . . . .  17
     B.2.  v19 to v20  . . . . . . . . . . . . . . . . . . . . . . .  17
     B.3.  v17 to v19  . . . . . . . . . . . . . . . . . . . . . . .  17
     B.4.  v16 to v17  . . . . . . . . . . . . . . . . . . . . . . .  17
     B.5.  v15 to v16  . . . . . . . . . . . . . . . . . . . . . . .  17
     B.6.  v14 to v15  . . . . . . . . . . . . . . . . . . . . . . .  18
     B.7.  v13 to v14  . . . . . . . . . . . . . . . . . . . . . . .  18



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     B.8.  v11 to v13  . . . . . . . . . . . . . . . . . . . . . . .  18
     B.9.  v10 to v11  . . . . . . . . . . . . . . . . . . . . . . .  18
     B.10. v09 to v10  . . . . . . . . . . . . . . . . . . . . . . .  18
     B.11. v08 to v09  . . . . . . . . . . . . . . . . . . . . . . .  18
     B.12. v07 to v08  . . . . . . . . . . . . . . . . . . . . . . .  18
     B.13. v06 to v07  . . . . . . . . . . . . . . . . . . . . . . .  18
     B.14. v05 to v06  . . . . . . . . . . . . . . . . . . . . . . .  18
     B.15. v03 to v04  . . . . . . . . . . . . . . . . . . . . . . .  19
     B.16. v01 to v03  . . . . . . . . . . . . . . . . . . . . . . .  19
     B.17. v00 to v01  . . . . . . . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   This document specifies the binding of a stream of events which form
   part of a dynamic subscription to the NETCONF protocol [RFC6241].
   Dynamic subscriptions are defined in
   [I-D.draft-ietf-netconf-subscribed-notifications].  In addition, as
   [I-D.draft-ietf-netconf-yang-push] is itself built upon
   [I-D.draft-ietf-netconf-subscribed-notifications], this document
   enables a NETCONF client to request via a dynamic subscription and
   receive updates from a YANG datastore located on a NETCONF server.

   This document assumes that the reader is familiar with the
   terminology and concepts defined in
   [I-D.draft-ietf-netconf-subscribed-notifications].

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The following terms are defined in
   [I-D.draft-ietf-netconf-subscribed-notifications]: dynamic
   subscription, event stream, notification message, publisher,
   receiver, subscriber, subscription.  No additional terms are defined.

3.  Compatibility with RFC-5277's create-subscription

   A publisher is allowed to concurrently support dynamic subscription
   RPCs of [I-D.draft-ietf-netconf-subscribed-notifications] at the same
   time as [RFC5277]'s "create-subscription" RPC.  However a single
   NETCONF transport session MUST NOT support both this specification
   and a subscription established by [RFC5277]'s "create-subscription"




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   RPC.  To protect against any attempts to use a single NETCONF
   transport session in this way:

   o  A solution MUST reply with the [RFC6241] "rpc-error" element
      containing the "error-tag" value of "operation-not-supported" if a
      "create-subscription" RPC is received on a NETCONF session where
      an [I-D.draft-ietf-netconf-subscribed-notifications] established
      subscription exists.
   o  A solution MUST reply with the [RFC6241] "rpc-error" element
      containing the "error-tag" value of "operation-not-supported" if
      an "establish-subscription" request has been received on a NETCONF
      session where the "create-subscription" RPC has successfully
      [RFC5277] created a subscription.

   If a publisher supports this specification but not subscriptions via
   [RFC5277], the publisher MUST NOT advertise
   "urn:ietf:params:netconf:capability:notification:1.0".

4.  Mandatory XML, event stream and datastore support

   The "encode-xml" feature of
   [I-D.draft-ietf-netconf-subscribed-notifications] MUST be supported.
   This indicates that XML is a valid encoding for RPCs, state change
   notifications, and subscribed content.

   A NETCONF publisher supporting event stream subscription via
   [I-D.draft-ietf-netconf-subscribed-notifications] MUST support the
   "NETCONF" event stream identified in that document.

5.  NETCONF connectivity and the Dynamic Subscriptions

   Management of dynamic subscriptions occurs via RPCs as defined in
   [I-D.draft-ietf-netconf-yang-push] and
   [I-D.draft-ietf-netconf-subscribed-notifications].  For a dynamic
   subscription, if the NETCONF session involved with the "establish-
   subscription" terminates, the subscription MUST be terminated.

   For a dynamic subscription, any "modify-subscription", "delete-
   subscription", or "resync-subscription" RPCs MUST be sent using the
   same NETCONF session upon which the referenced subscription was
   established.

6.  Notification Messages

   Notification messages transported over the NETCONF protocol MUST be
   encoded in a <notification> message as defined within [RFC5277],
   Section 4.  And per [RFC5277]'s "eventTime" object definition, the
   "eventTime" populated with the event occurrence time.



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   For dynamic subscriptions, all notification messages MUST use the
   NETCONF transport session used by the "establish-subscription" RPC.

7.  Dynamic Subscriptions and RPC Error Responses

   When an RPC error occurs as defined in
   [I-D.draft-ietf-netconf-subscribed-notifications] Section 2.4.6 and
   [I-D.draft-ietf-netconf-yang-push] Appendix A, the NETCONF RPC reply
   MUST include an "rpc-error" element per [RFC6241] with the error
   information populated as follows:

   o  An "error-type" node of "application".
   o  An "error-tag" node with the value being a string that corresponds
      to an identity associated with the error.  For the mechanisms
      specified in this document, this "error-tag" will come from one of
      two places.  Either it will correspond to the error identities
      within [I-D.draft-ietf-netconf-subscribed-notifications] section
      2.4.6 for general subscription errors:

             error identity         uses error-tag
             ---------------------- --------------
             dscp-unavailable       invalid-value
             encoding-unsupported   invalid-value
             filter-unsupported     invalid-value
             insufficient-resources resource-denied
             no-such-subscription   invalid-value
             replay-unsupported     operation-not-supported

      Or this "error-tag" will correspond to the error identities within
      [I-D.draft-ietf-netconf-yang-push] Appendix A.1 for subscription
      errors specific to YANG datastores:

             error identity              uses error-tag
             ----------------------      --------------
             cant-exclude                operation-not-supported
             datastore-not-subscribable  invalid-value
             no-such-subscription-resync invalid-value
             on-change-unsupported       operation-not-supported
             on-change-sync-unsupported  operation-not-supported
             period-unsupported          invalid-value
             update-too-big              too-big
             sync-too-big                too-big
             unchanging-selection        operation-failed

   o  an "error-severity" of "error" (this MAY be included).
   o  an "error-app-tag" node with the value being a string that
      corresponds to an identity associated with the error, as defined
      in [I-D.draft-ietf-netconf-subscribed-notifications] section 2.4.6



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      for general subscriptions, and [I-D.draft-ietf-netconf-yang-push]
      Appendix A.1, for datastore subscriptions.  The specific identity
      to use depends on the RPC for which the error occurred.  Each
      error identity will be inserted as the "error-app-tag" following
      the form <modulename>:<identityname>.  An example of such as valid
      encoding would be "ietf-subscribed-notifications:no-such-
      subscription".  Viable errors for different RPCs are as follows:

            RPC                     have base identity
            ----------------------  ----------------------------
            establish-subscription  establish-subscription-error
            modify-subscription     modify-subscription-error
            delete-subscription     delete-subscription-error
            kill-subscription       delete-subscription-error
            resync-subscription     resync-subscription-error

   o  In case of error responses to an "establish-subscription" or
      "modify-subscription" request there is the option of including an
      "error-info" node.  This node may contain XML-encoded data with
      hints for parameter settings that might lead to successful RPC
      requests in the future.  Following are the yang-data structures
      from [I-D.draft-ietf-netconf-subscribed-notifications] and
      [I-D.draft-ietf-netconf-yang-push] which may be returned:

      establish-subscription returns hints in yang-data structure
      ---------------------- ------------------------------------
      target: event stream   establish-subscription-stream-error-info
      target: datastore      establish-subscription-datastore-error-info

      modify-subscription    returns hints in yang-data structure
      ---------------------- ------------------------------------
      target: event stream   modify-subscription-stream-error-info
      target: datastore      modify-subscription-datastore-error-info

      The yang-data included within "error-info" SHOULD NOT include the
      optional leaf "reason", as such a leaf would be redundant
      with information that is already placed within the
      "error-app-tag".

   In case of an rpc error resulting from a "delete-subscription",
   "kill-subscription", or "resync-subscription" request, no "error-
   info" needs to be included, as the "subscription-id" is the only RPC
   input parameter and no hints regarding this RPC input parameters need
   to be provided.







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8.  Security Considerations

   This document does not introduce additional Security Considerations
   for dynamic subscriptions beyond those discussed in
   [I-D.draft-ietf-netconf-subscribed-notifications].  But there is one
   consideration worthy of more refinement based on the connection
   oriented nature of the NETCONF protocol.  Specifically, if a buggy or
   compromised 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 in order to reclaim resources
   and preserve normal operation for the other subscriptions.

9.  IANA Considerations

   This document has no actions for IANA.

10.  Acknowledgments

   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,
   Qin Wu, and Guangying Zheng.

11.  References

11.1.  Normative References

   [I-D.draft-ietf-netconf-subscribed-notifications]
              Voit, E., Clemm, A., Gonzalez Prieto, A., Tripathy, A.,
              and E. Nilsen-Nygaard, "Customized Subscriptions to a
              Publisher's Event Streams", September 2018,
              <https://datatracker.ietf.org/doc/
              draft-ietf-netconf-subscribed-notifications/>.

   [I-D.draft-ietf-netconf-yang-push]
              Clemm, Alexander., Voit, Eric., Gonzalez Prieto, Alberto.,
              Tripathy, A., Nilsen-Nygaard, E., Bierman, A., and B.
              Lengyel, "YANG Datastore Subscription", September 2018,
              <https://datatracker.ietf.org/doc/
              draft-ietf-netconf-yang-push/>.







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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5277]  Chisholm, S. and H. Trevino, "NETCONF Event
              Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008,
              <https://www.rfc-editor.org/info/rfc5277>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

11.2.  Informative References

   [RFC8347]  Liu, X., Ed., Kyparlis, A., Parikh, R., Lindem, A., and M.
              Zhang, "A YANG Data Model for the Virtual Router
              Redundancy Protocol (VRRP)", RFC 8347,
              DOI 10.17487/RFC8347, March 2018,
              <https://www.rfc-editor.org/info/rfc8347>.

   [XPATH]    Clark, J. and S. DeRose, "XML Path Language (XPath)
              Version 1.0", November 1999,
              <http://www.w3.org/TR/1999/REC-xpath-19991116>.

Appendix A.  Examples

   This section is non-normative.  Additionally the subscription "id"
   values of 22, 23, and 39 used below are just examples.  In
   production, the actual values of "id" may not be small integers.

A.1.  Event Stream Discovery

   As defined in [I-D.draft-ietf-netconf-subscribed-notifications] 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
   [I-D.draft-ietf-netconf-subscribed-notifications] Section 3.1.

   The following example illustrates the retrieval of the list of
   available event streams:




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<rpc message-id="101"
  xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <get>
    <filter type="subtree">
      <streams
     xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"/>
    </filter>
  </get>
</rpc>

                       Figure 1: Get streams request

   After such a request, the NETCONF publisher returns a list of event
   streams available, as well as additional information which might
   exist in the container.

A.2.  Dynamic Subscriptions

A.2.1.  Establishing Dynamic Subscriptions

   The following figure shows two successful "establish-subscription"
   RPC requests as per
   [I-D.draft-ietf-netconf-subscribed-notifications].  The first request
   is given a subscription "id" of 22, the second, an "id" of 23.



























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      +------------+                 +-----------+
      | Subscriber |                 | Publisher |
      +------------+                 +-----------+
            |                              |
            |    Capability Exchange       |
            |<---------------------------->|
            |                              |
            |                              |
            |    establish-subscription    |
            |----------------------------->|  (a)
            | RPC Reply: OK, id = 22       |
            |<-----------------------------|  (b)
            |                              |
            | notification message (for 22)|
            |<-----------------------------|
            |                              |
            |                              |
            |    establish-subscription    |
            |----------------------------->|
            | notification message (for 22)|
            |<-----------------------------|
            | RPC Reply: OK, id = 23       |
            |<-----------------------------|
            |                              |
            |                              |
            | notification message (for 22)|
            |<-----------------------------|
            | notification message (for 23)|
            |<-----------------------------|
            |                              |

          Figure 2: Multiple subscriptions over a NETCONF session

   To provide examples of the information being transported, example
   messages for interactions (a) and (b) in Figure 2 are detailed below:

<rpc message-id="102" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <establish-subscription
      xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
    <stream-xpath-filter xmlns:ex="http://example.com/events">
      /ex:foo/
    </stream-xpath-filter>
    <stream>NETCONF</stream>
    <dscp>10</dscp>
  </establish-subscription>
</rpc>

               Figure 3: establish-subscription request (a)



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

  <rpc-reply message-id="102"
    xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
    <id
      xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
      22
    </id>
  </rpc-reply>

               Figure 4: establish-subscription success (b)

   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
   Figure 3 proved unacceptable, the publisher may have returned:

   <rpc-reply message-id="102"
     xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <rpc-error>
      <error-type>application</error-type>
      <error-tag>invalid-value</error-tag>
      <error-severity>error</error-severity>
      <error-app-tag>
        ietf-subscribed-notifications:dscp-unavailable
      </error-app-tag>
     </rpc-error>
   </rpc-reply>

             Figure 5: an unsuccessful establish subscription

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

A.2.2.  Modifying Dynamic Subscriptions

   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.







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

   Figure 6: Interaction model for successful subscription modification

   If the subscription being modified in Figure 6 is a datastore
   subscription as per [I-D.draft-ietf-netconf-yang-push], the
   modification request made in (c) may look like that shown in
   Figure 7.  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.

<rpc message-id="303"
  xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <modify-subscription
       xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
       xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
    <id>23</id>
    <yp:datastore-xpath-filter xmlns:ex="http://example.com/datastore">
        /ex:foo/ex:bar
    </yp:datastore-xpath-filter>
    <yp:periodic>
      <yp:period>500</yp:period>
    </yp:periodic>
  </modify-subscription>
</rpc>

              Figure 7: Subscription modification request (c)





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   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:

   <rpc-reply message-id="303"
     xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <rpc-error>
       <error-type>application</error-type>
       <error-tag>invalid-value</error-tag>
       <error-severity>error</error-severity>
       <error-app-tag>
           ietf-yang-push:period-unsupported
       </error-app-tag>
       <error-info>
         <modify-subscription-datastore-error-info
             xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push">
           <period-hint>
               3000
           </period-hint>
         </modify-subscription-datastore-error-info>
       </error-info>
     </rpc-error>
   </rpc-reply>

            Figure 8: Modify subscription failure with hint (d)

A.2.3.  Deleting Dynamic Subscriptions

   The following demonstrates deleting a subscription.  This
   subscription may have been to either a stream or a datastore.

  <rpc message-id="103"
    xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
    <delete-subscription
      xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
      <id>22</id>
    </delete-subscription>
  </rpc>

                       Figure 9: Delete subscription

   If the NETCONF publisher can satisfy the request, the publisher
   replies with success to the RPC request.





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   If the NETCONF publisher cannot satisfy the request, the publisher
   sends an error-rpc element indicating the modification didn't work.
   Figure 10 shows a valid response for existing valid subscription
   "id", but that subscription "id" was created on a different NETCONF
   transport session:

   <rpc-reply message-id="103"
     xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <rpc-error>
       <error-type>application</error-type>
       <error-tag>invalid-value</error-tag>
       <error-severity>error</error-severity>
       <error-app-tag>
           ietf-subscribed-notifications:no-such-subscription
       </error-app-tag>
     </rpc-error>
   </rpc-reply>

                Figure 10: Unsuccessful delete subscription

A.3.  Subscription State Notifications

   A publisher will send subscription state notifications for dynamic
   subscriptions according to the definitions within
   [I-D.draft-ietf-netconf-subscribed-notifications].

A.3.1.  subscription-modified

   As per Section 2.7.2 of
   [I-D.draft-ietf-netconf-subscribed-notifications], a "subscription-
   modified" might be sent over NETCONF if the definition of a
   configured filter changes.  A subscription state notification encoded
   in XML would look like:

<notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
  <eventTime>2007-09-01T10:00:00Z</eventTime>
  <subscription-modified
      xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
    <id>39</id>
    <stream-xpath-filter xmlns:ex="http://example.com/events">
      /ex:foo
    </stream-xpath-filter>
    <stream>NETCONF</stream>
  </subscription-modified>
</notification>

     Figure 11: subscription-modified subscription state notification




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A.3.2.  subscription-resumed, and replay-complete

   A "subscription-resumed" would look like:

  <notification
    xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
    <eventTime>2007-09-01T10:00:00Z</eventTime>
    <subscription-resumed
      xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
      <id>39</id>
    </subscription-resumed>
  </notification>

            Figure 12: subscription-resumed notification in XML

   The "replay-complete" is virtually identical, with "subscription-
   resumed" simply being replaced by "replay-complete".

A.3.3.  subscription-terminated and subscription-suspended

   A "subscription-terminated" would look like:

  <notification
    xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
    <eventTime>2007-09-01T10:00:00Z</eventTime>
    <subscription-terminated
      xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
      <id>39</id>
      <reason>
         suspension-timeout
      </reason>
    </subscription-terminated>
  </notification>

    Figure 13: subscription-terminated subscription state notification

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

A.4.  Filter Examples

   This section provides examples which illustrate both XPath and
   subtree methods of filtering event record contents.  The examples are
   based on the YANG notification "vrrp-protocol-error-event" as defined
   per the ietf-vrrp.yang model within [RFC8347].  Event records based
   on this specification which are generated by the publisher might
   appear as:



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  <notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
    <eventTime>2018-09-14T08:22:33.44Z</eventTime>
    <vrrp-protocol-error-event
         xmlns="urn:ietf:params:xml:ns:yang:ietf-vrrp">
       <protocol-error-reason>checksum-error</protocol-error-reason>
    </vrrp-protocol-error-event>
  </notification>

             Figure 14: RFC 8347 (VRRP) - Example Notification

   Suppose a subscriber wanted to establish a subscription which only
   passes instances of event records where there is a "checksum-error"
   as part of a VRRP protocol event.  Also assume the publisher places
   such event records into the NETCONF stream.  To get a continuous
   series of matching event records, the subscriber might request the
   application of an XPath filter against the NETCONF stream.  An
   "establish-subscription" RPC to meet this objective might be:

 <rpc message-id="601" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
   <establish-subscription
     xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
     <stream>NETCONF</stream>
     <stream-xpath-filter xmlns="urn:ietf:params:xml:ns:yang:ietf-vrrp">
       /vrrp-protocol-error-event[
          vrrp:protocol-error-reason="vrrp:checksum-error"]
     </stream-xpath-filter>
   </establish-subscription>
 </rpc>

       Figure 15: Establishing a subscription error reason via XPath

   For more examples of XPath filters, see [XPATH].

   Suppose the "establish-subscription" in Figure 15 was accepted.  And
   suppose later a subscriber decided they wanted to broaden this
   subscription cover to all VRRP protocol events (i.e., not just those
   with a "checksum error").  The subscriber might attempt to modify the
   subscription in a way which replaces the XPath filter with a subtree
   filter which sends all VRRP protocol events to a subscriber.  Such a
   "modify-subscription" RPC might look like:











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 <rpc message-id="602" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
   <modify-subscription
      xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications">
     <id>99</id>
     <stream-subtree-filter>
      <vrrp-protocol-error-event
             xmlns="urn:ietf:params:xml:ns:yang:ietf-vrrp"/>
     </stream-subtree-filter>
   </modify-subscription>
 </rpc>

                                 Figure 16

   For more examples of subtree filters, see [RFC6241], section 6.4.

Appendix B.  Changes between revisions

   (To be removed by RFC editor prior to publication)

B.1.  v20 to v21

   o  Including Tom Petch's text to resolve the meaning of 'binding'.
   o  A few small wording tweaks.

B.2.  v19 to v20

   o  Notes to RFC editor removed, consideration moved under Figure 10
      in SN.

B.3.  v17 to v19

   o  Per Benjamin Kaduk's discuss on SN, adjusted IPR to
      pre5378Trust200902

B.4.  v16 to v17

   o  During the SN YANG Doctor review, a suggestion was made to update
      the error-tags to make the mechanism work with embedded NETCONF
      and RESTCONF error reporting.
   o  Minor text tweaks from review.

B.5.  v15 to v16

   o  During the shepherd review, two clarifications were requested
      which do not impact the technical details of this document.  These
      clarifications were: (a) further describing that dynamic
      subscriptions can have state change notifications, and (b) more
      details about the recommended text refinement desired for RFC6241.



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B.6.  v14 to v15

   o  Per Kent's request, added name attribute to artwork.  This would
      be needed for an automated extraction.

B.7.  v13 to v14

   o  Title change.

B.8.  v11 to v13

   o  Subscription identifier renamed to id.
   o  Appendix A.4 for filter examples
   o  for v13, Tweak of example to /foo/bar

B.9.  v10 to v11

   o  Configured removed.

B.10.  v09 to v10

   o  Tweaks to examples and text.
   o  Downshifted state names.
   o  Removed address from examples.

B.11.  v08 to v09

   o  Tweaks based on Kent's comments.
   o  Updated examples in Appendix A.  And updates to some object names
      based on changes in the subscribed-notifications draft.
   o  Added a YANG model for the NETCONF identity.

B.12.  v07 to v08

   o  Tweaks and clarification on :interleave.

B.13.  v06 to v07

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

B.14.  v05 to v06

   o  Moved examples to appendices
   o  All examples rewritten based on namespace learnings
   o  Normative text consolidated in front
   o  Removed all mention of JSON
   o  Call home process detailed



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   o  Note: this is a major revision attempting to cover those comments
      received from two week review.

B.15.  v03 to v04

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

B.16.  v01 to v03

   o  Text simplifications throughout
   o  v02 had no meaningful changes

B.17.  v00 to v01

   o  Added Call Home in solution for configured subscriptions.
   o  Clarified support for multiple subscription on a single session.
      No need to support multiple create-subscription.
   o  Added mapping between terminology in yang-push and [RFC6241] (the
      one followed in this document).
   o  Editorial improvements.

Authors' Addresses

   Eric Voit
   Cisco Systems

   Email: evoit@cisco.com


   Alexander Clemm
   Huawei

   Email: ludwig@clemm.org


   Alberto Gonzalez Prieto
   Microsoft

   Email: alberto.gonzalez@microsoft.com








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   Einar Nilsen-Nygaard
   Cisco Systems

   Email: einarnn@cisco.com


   Ambika Prasad Tripathy
   Cisco Systems

   Email: ambtripa@cisco.com









































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