NETCONF Support for Event Notifications
draft-ietf-netconf-netconf-event-notifications-05

NETCONF                                               A. Gonzalez Prieto
Internet-Draft                                                    VMware
Intended status: Standards Track                                A. Clemm
Expires: April 5, 2018                                            Huawei
                                                                 E. Voit
                                                       E. Nilsen-Nygaard
                                                             A. Tripathy
                                                           Cisco Systems
                                                         October 2, 2017


                NETCONF Support for Event Notifications
           draft-ietf-netconf-netconf-event-notifications-05

Abstract

   This document defines how to transport network subscriptions and
   event messages on top of the Network Configuration protocol
   (NETCONF).  This includes the full set of RPCs, subscription state
   changes, and subscribed content needing asynchronous delivery.

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
   and may be updated, replaced, or obsoleted by other documents at any
   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 April 5, 2018.

Copyright Notice

   Copyright (c) 2017 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Solution  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Event Stream Discovery  . . . . . . . . . . . . . . . . .   3
     3.2.  Mandatory NETCONF support . . . . . . . . . . . . . . . .   4
     3.3.  Dynamic Subscriptions . . . . . . . . . . . . . . . . . .   4
     3.4.  Configured Subscriptions  . . . . . . . . . . . . . . . .  11
   4.  Interleave Capability . . . . . . . . . . . . . . . . . . . .  23
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  24
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  24
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  25
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  25
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  25
   Appendix A.  Open Items . . . . . . . . . . . . . . . . . . . . .  26
   Appendix B.  Changes between revisions  . . . . . . . . . . . . .  26
     B.1.  v04 to v05  . . . . . . . . . . . . . . . . . . . . . . .  26
     B.2.  v03 to v04  . . . . . . . . . . . . . . . . . . . . . . .  26
     B.3.  v01 to v03  . . . . . . . . . . . . . . . . . . . . . . .  26
     B.4.  v00 to v01  . . . . . . . . . . . . . . . . . . . . . . .  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27

1.  Introduction

   This document defines mechanisms that provide a subscription and
   asynchronous message notification delivery service for the NETCONF
   protocol [RFC6241] based on [subscribe].  This is an optional
   capability built on top of the base NETCONF definition.

2.  Terminology

   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 [RFC2119].

   The following terms are defined in [RFC6241]: client, server,
   operation, RPC.

   The following terms are defined in [subscribe]: event, event
   notification, stream, publisher, receiver, subscriber, subscription,
   configured subscription.




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   Note that a publisher in [subscribe] corresponds to a server in
   [RFC6241].  Similarly, a subscriber corresponds to a client.  A
   receiver is also a client.  In the remainder of this document, we
   will use the terminology in [RFC6241].

3.  Solution

   In this section, we describe and exemplify how [subscribe] is to be
   supported over NETCONF.

3.1.  Event Stream Discovery

   In the context of [subscribe] 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 server
   using the "get" operation against the top-level container "/streams"
   defined in [subscribe].  The reply includes the list of streams
   supported on the NETCONF server.

   The following example illustrates the retrieval of the list of
   available event streams using the <get> operation.

      <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-yang-push:1.0"/>
            </filter>
        </get>
      </rpc>

                       Figure 1: Get streams request

   The NETCONF server returns a list of event streams available.  In
   this example, the list contains the NETCONF, SNMP, and SYSLOG
   streams.














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   <rpc-reply message-id="101"
           xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <data>
       <streams
          xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
         <stream>
           <stream>NETCONF</stream>
           <description>The NETCONF mandatory event stream</description>
         </stream>
         <stream>
           <stream>SNMP</stream>
           <description>The SNMP event stream</description>
         </stream>
         <stream>
           <stream>SYSLOG</stream>
           <description>The SYSLOG event stream</description>
           <replay-support/>
           <replay-log-creation-time>
             2015-03-09T19:14:55.233Z</replay-log-creation-time>
         </stream>
       </streams>
     </data>
   </rpc-reply>

                      Figure 2: Get streams response

   For [yang-push], a similar get is needed to retrieve available
   datastore names.

3.2.  Mandatory NETCONF support

   A NETCONF server implementation supporting [subscribe] must support
   dynamic subscriptions and the "NETCONF" notification event stream.
   The NETCONF event stream contains all NETCONF XML event information
   supported by the server.

   A NETCONF server implementation supporting [yang-push] must support
   the "running" datastore.

3.3.  Dynamic Subscriptions

3.3.1.  Establishing Dynamic Subscriptions

   The dynamic subscription RFC and interactions operation is defined in
   [subscribe].






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3.3.1.1.  Usage Example

   An example of interactions over NETCONF transport for one sample
   subscription is below:

     <netconf:rpc netconf:message-id="102"
            xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
       <establish-subscription
                xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
          <stream>NETCONF</stream>
          <event-filter-type>xpath-event-filter</event-filter-type>
          <event-filter-contents xmlns:ex="http://example.com/event/1.0"
                  select="/ex:event[ex:eventClass='fault' and
                           (ex:severity='minor' or ex:severity='major'
                            or ex:severity='critical')]" />
       </establish-subscription>
     </netconf:rpc>

               Figure 3: establish-subscription over NETCONF

3.3.1.2.  Positive Response

   If the NETCONF server can satisfy the request, the server sends a
   positive <subscription-result> element, and the subscription-id of
   the accepted subscription.

      <rpc-reply message-id="102"
             xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
        <subscription-result
                xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
          ok
        </subscription-result>
        <identifier
                xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
          52
        </identifier>
      </rpc-reply>

                Figure 4: Successful establish-subscription

3.3.1.3.  Negative Response

   If the NETCONF server cannot satisfy the request, or the client has
   no authorization to establish the subscription, the server will send
   a negative <subscription-result> element.  For instance:






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      <rpc-reply message-id="103"
             xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
        <subscription-result
                 xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
          stream-unavailable
        </subscription-result>
      </rpc-reply>

               Figure 5: Unsuccessful establish subscription

3.3.1.4.  Subscription Negotiation

   If the client request includes parameters the NETCONF server cannot
   serve, the negative <subscription-result> may include hints at
   subscription parameters which would have been accepted.  For
   instance, consider the following subscription from [yang-push], which
   augments the establish-subscription with some additional parameters,
   including "period".  If the client requests a period which the
   NETCONF server cannot serve, the back-and-forth exchange may be:

      <netconf:rpc message-id="101"
         xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
         <establish-subscription
               xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
            <datastore>running</datastore>
            <event-filter-type>
              subtree</event-filter-type>
            <event-filter-contents
                  xmlns:ex="http://example.com/sample-data/1.0">
                  select="/ex:foo" />
            <dampening-period>10</dampening-period>
            <encoding>encode-xml</encoding>
         </establish-subscription>
      </netconf:rpc>

      <rpc-reply message-id="101"
            xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
        <subscription-result
              xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
          error-insufficient-resources
        </subscription-result>
        <period-hint
              xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
          2000
        </period-hint>
      </rpc-reply>

             Figure 6: Subscription establishment negotiation



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3.3.1.5.  Message Flow Examples


   +------------+                 +-----------+
   |   Client   |                 |   Server  |
   +------------+                 +-----------+
         |                              |
         |    Capability Exchange       |
         |<---------------------------->|
         |                              |
         |                              |
         |    Establish Subscription    |
         |----------------------------->|
         | RPC Reply: OK, id = 22       |
         |<-----------------------------|
         |                              |
         |  Notification (id 22)        |
         |<-----------------------------|
         |                              |
         |                              |
         |    Establish Subscription    |
         |----------------------------->|
         | RPC Reply: OK, id = 23       |
         |<-----------------------------|
         |                              |
         |                              |
         |  Notification (id 22)        |
         |<-----------------------------|
         |  Notification (id 23)        |
         |<-----------------------------|
         |                              |
         |                              |

   Figure 7: Multiple subscription establishments over a single NETCONF
                                  session

3.3.2.  Modifying a Subscription

   This operation is defined in [subscribe].

3.3.2.1.  Usage Example

   The following demonstrates modifying a subscription.  Consider a
   subscription from [yang-push], which augments the establish-
   subscription with some additional parameters, including "period".  A
   subscription may be established and modified as follows.





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    <netconf:rpc message-id="101"
           xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
      <establish-subscription
               xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
         <datastore xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push">
            running</datastore>
         <event-filter-type>subtree-event-filter</event-filter-type>
         <event-filter-contents
           xmlns:ex="http://example.com/sample-data/1.0">
           select="/ex:foo" />
         <period xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
             1000
         </period>
      </establish-subscription>
    </netconf:rpc>

    <rpc-reply message-id="101"
           xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
      <subscription-result
               xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
        ok
      </subscription-result>
      <identifier
               xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
        1922
      </identifier>
    </rpc-reply>


    <netconf:rpc message-id="102"
           xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
      <modify-subscription
               xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
        <identifier>1922</identifier>
        <period>100</period>
      </modify-subscription>
    </netconf:rpc>


                    Figure 8: Subscription modification

3.3.2.2.  Positive Response

   If the NETCONF server can satisfy the request, the server sends a
   positive <subscription-result> element.  This response is like that
   to an establish-subscription request, but without the subscription
   identifier.




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      <rpc-reply message-id="102"
             xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
        <subscription-result
                 xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
          ok
        </subscription-result>
      </rpc-reply>


                 Figure 9: Successful modify subscription

3.3.2.3.  Negative Response

   If the NETCONF server cannot satisfy the request, the server sends a
   negative <subscription-result> element.  Its contents and semantics
   are identical to those in an establish-subscription request.  For
   instance:

      <rpc-reply message-id="102"
             xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
        <subscription-result
                 xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
          period-unsupported
        </subscription-result>
        <period-hint>500</period-hint>
      </rpc-reply>


                Figure 10: Unsuccessful modify subscription

3.3.2.4.  Message Flow Example




















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   +------------+                 +-----------+
   |   Client   |                 |   Server  |
   +------------+                 +-----------+
         |                              |
         |    Capability Exchange       |
         |<---------------------------->|
         |                              |
         |    Establish Subscription    |
         |----------------------------->|
         | RPC Reply: OK, id = 22       |
         |<-----------------------------|
         |                              |
         |  Notification (id 22)        |
         |<-----------------------------|
         |                              |
         | Modify Subscription (id 22)  |
         |----------------------------->|
         | RPC Reply: OK                |
         |<-----------------------------|
         |                              |
         |  Notification (id 22)        |
         |<-----------------------------|
         |                              |

     Figure 11: Message flow for successful subscription modification

3.3.3.  Deleting a Subscription

   This operation is defined in [subscribe] for events, and enhanced in
   [yang-push] for datastores.

3.3.3.1.  Usage Example

   The following demonstrates deleting a subscription.

      <netconf:rpc message-id="101"
             xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
        <delete-subscription
                 xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
          <identifier>1922</identifier>
        </delete-subscription>
      </netconf:rpc>

                      Figure 12: Delete subscription







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3.3.3.2.  Positive Response

   If the NETCONF server can satisfy the request, the server sends a
   positive <subscription-result> element.  For example:

      <rpc-reply message-id="103"
             xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
        <subscription-result
                xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
          ok
        </subscription-result>
      </rpc-reply>

                 Figure 13: Successful delete subscription

3.3.3.3.  Negative Response

   If the NETCONF server cannot satisfy the request, the server sends an
   <subscription-result> element indicating the deletion was not
   performed.  For example:

      <rpc-reply message-id="101"
             xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
        <subscription-result
                xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
          no-such-subscription
        </subscription-result>
      </rpc-reply>

                Figure 14: Unsuccessful delete subscription

3.4.  Configured Subscriptions

   Configured subscriptions are established, modified, and deleted using
   configuration operations against the top-level subtree of [subscribe]
   or [yang-push] via configuration interface.  This document covers
   configured subscriptions where the chosen protocol to send the
   notifications to the receivers is NETCONF.

   Configured subscriptions are supported by NETCONF servers using
   NETCONF Call Home [RFC8071].

   Any configuration interface can be used to set a configured
   subscription that uses NETCONF to push notifications to receivers.
   Without loss of generality, the examples in this section, use a
   NETCONF interface to configure the subscriptions





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3.4.1.  Establishing a Configured Subscription

   For subscription establishment, a NETCONF client may send:

     <rpc message-id="101"
            xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <edit-config>
         <target>
           <running/>
         </target>
         <subscription-config
                 xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
           <subscription>
             <identifier>
               1922
             </identifier>
             <stream>
               foo
             </stream>
             <receiver>
               <address>
                 1.2.3.4
               </address>
               <port>
                 1234
               </port>
               <protocol>
                 netconf
               </protocol>
             </receiver>
           </subscription>
         </subscription-config>
       </edit-config>
     </rpc>


               Figure 15: Establish configured subscription

   if the request is accepted, the server would reply:

      <rpc-reply message-id="101"
                xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
        <ok/>
      </rpc-reply>


      Figure 16: Response to a successful configuration subscription
                               establishment



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   if the request is not accepted because the server cannot serve it, no
   configuration is changed.  Int this case the server may reply:

   <rpc-reply xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <subscription-result
                xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
       error-insufficient-resources
     </subscription-result>
   </rpc-reply>

   Figure 17: Response to a failed configured subscription establishment

   For every configured receiver, once NETCONF transport session between
   the server and the receiver is recognized as active, the server will
   issue a "subscription-started" notification.  After that, the server
   will send notifications to the receiver as per the subscription
   notification.  Note that the server assumes that the receiver is
   ready to accept notifications on the NETCONF session.  This may
   require coordination between the client that configures the
   subscription and the clients for which the notifications are
   intended.  This coordination is out of the scope of this document.

   The session is only intended for pushing notifications.  Client
   requests on that session SHOULD be ignored by the server.

   The contents sent by the server on the Call Home session, once
   established, are identical to those in a dynamic subscription.

3.4.2.  Call Home for Configured Subscriptions

   Once the subscription configuration is active, if NETCONF transport
   is needed but does not exist to one or more target IP address plus
   port, the server initiates a transport session via [RFC8071] to those
   receiver(s) in the subscription using the address and port specified.

3.4.3.  Full Establish Message Flow















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 +----------+                 +-----------+     +---------+  +---------+
 |  Client  |                 |   Server  |     | Rcver A |  | Rcver B |
 +----------+                 +-----------+     +---------+  +---------+
       |                            |                |            |
       |    Capability Exchange     |                |            |
       |<-------------------------->|                |            |
       |                            |                |            |
       |                            |                |            |
       |        Edit-config         |                |            |
       |--------------------------->|                |            |
       |       RPC Reply: OK        |                |            |
       |<---------------------------|                |            |
       |                            |   Call Home    |            |
       |                            |<-------------->|            |
       |                            |<--------------------------->|
       |                            |                |            |
       |                            |  Subscription  |            |
       |                            |  Started       |            |
       |                            |  (id 22)       |            |
       |                            |--------------->|            |
       |                            |---------------------------->|
       |                            |                |            |
       |                            |  Notification  |            |
       |                            |  (id 22)       |            |
       |                            |--------------->|            |
       |                            |---------------------------->|
       |                            |                |            |

     Figure 18: Message flow for configured subscription establishment

3.4.4.  Modifying a Configured Subscription

   Configured subscriptions can be modified using configuration
   operations against the top-level subtree subscription-config.

   For example, the subscription established in the previous section
   could be modified as follows, choosing a different receiver:














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     <rpc message-id="102"
            xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
       <edit-config>
         <target>
           <running/>
         </target>
         <subscription-config
                 xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
           <subscription>
             <identifier>
               1922
             </identifier>
             <stream>
               foo
             </stream>
             <receiver>
               <address>
                 1.2.3.5
               </address>
               <port>
                 1234
               </port>
             </receiver>
           </subscription>
         </subscription-config>
       </edit-config>
     </rpc>

                 Figure 19: Modify configured subscription

   if the request is accepted, the server would reply:

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

       Figure 20: A successful configured subscription modification

3.4.4.1.  Message Flow Example











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 +----------+                 +-----------+     +---------+  +---------+
 |  Client  |                 |   Server  |     | Rcver A |  | Rcver B |
 +----------+                 +-----------+     +---------+  +---------+
       |                            |                |            |
       |    Capability Exchange     |                |            |
       |<-------------------------->|                |            |
       |                            |                |            |
       |                            |                |            |
       |        Edit-config         |                |            |
       |--------------------------->|                |            |
       |       RPC Reply: OK        |                |            |
       |<---------------------------|                |            |
       |                            |   Call Home    |            |
       |                            |<-------------->|            |
       |                            |<--------------------------->|
       |                            |                |            |
       |                            |  Subscription  |            |
       |                            |  Started       |            |
       |                            |  (id 22)       |            |
       |                            |--------------->|            |
       |                            |---------------------------->|
       |                            |                |            |
       |                            |  Notification  |            |
       |                            |  (id 22)       |            |
       |                            |--------------->|            |
       |                            |---------------------------->|
       |                            |                |            |
       |        Edit-config         |                |            |
       |--------------------------->|                |            |
       |       RPC Reply: OK        |                |            |
       |<---------------------------|                |            |
       |                            |  Subscription  |            |
       |                            |  Modified      |            |
       |                            |  (id 22)       |            |
       |                            |--------------->|            |
       |                            |---------------------------->|
       |                            |                |            |
       |                            |  Notification  |            |
       |                            |  (id 22)       |            |
       |                            |--------------->|            |
       |                            |---------------------------->|
       |                            |                |            |


     Figure 21: Message flow for subscription modification (configured
                               subscription)





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3.4.5.  Deleting a Configured Subscription

   Subscriptions can be deleted using configuration operations against
   the top-level subtree subscription-config.  For example:

      <rpc message-id="103"
             xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
        <edit-config>
          <target>
            <running/>
          </target>
          <subscription-config
              xmlns:xc="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
            <subscription xc:operation="delete">
              <identifier>
                1922
              </identifier>
            </subscription>
          </subscription-config>
        </edit-config>
      </rpc>

      <rpc-reply message-id="103"
             xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
        <ok/>
      </rpc-reply>


               Figure 22: Deleting a configured subscription

3.4.5.1.  Message Flow Example




















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 +----------+                 +-----------+     +---------+  +---------+
 |  Client  |                 |   Server  |     | Rcver A |  | Rcver B |
 +----------+                 +-----------+     +---------+  +---------+
       |                            |                |            |
       |    Capability Exchange     |                |            |
       |<-------------------------->|                |            |
       |                            |                |            |
       |                            |                |            |
       |        Edit-config         |                |            |
       |--------------------------->|                |            |
       |       RPC Reply: OK        |                |            |
       |<---------------------------|                |            |
       |                            |   Call Home    |            |
       |                            |<-------------->|            |
       |                            |<--------------------------->|
       |                            |                |            |
       |                            |  Subscription  |            |
       |                            |  Started       |            |
       |                            |  (id 22)       |            |
       |                            |--------------->|            |
       |                            |---------------------------->|
       |                            |                |            |
       |                            |                |            |
       |                            |  Notification  |            |
       |                            |  (id 22)       |            |
       |                            |--------------->|            |
       |                            |---------------------------->|
       |                            |                |            |
       |        Edit-config         |                |            |
       |--------------------------->|                |            |
       |       RPC Reply: OK        |                |            |
       |<---------------------------|                |            |
       |                            |  Subscription  |            |
       |                            |  Terminated    |            |
       |                            |  (id 22)       |            |
       |                            |--------------->|            |
       |                            |---------------------------->|
       |                            |                |            |

       Figure 23: Message flow for subscription deletion (configured
                               subscription)

3.4.6.  Event (Data Plane) Notifications

   Once a dynamic or configured subscription has been created, the
   NETCONF server sends (asynchronously) event notifications from the
   subscribed stream to receiver(s) over NETCONF.  We refer to these as




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   data plane notifications.  The data model for Event Notifications is
   defined in [subscribe].

   The following is an example of an event notification from [RFC6020]:

      notification link-failure {
        description "A link failure has been detected";
          leaf if-name {
            type leafref {
              path "/interface/name";
            }
          }
          leaf if-admin-status {
            type admin-status;
          }
          leaf if-oper-status {
            type oper-status;
          }
      }

              Figure 24: Definition of an event notification

   This notification might result in the following, prior to it being
   placed into NETCONF.  Note that the mandatory eventTime and
   Subscription id have been added.

      <notification
             xmlns=" urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
        <eventTime>2007-09-01T10:00:00Z</eventTime>
        <link-failure xmlns="http://acme.example.com/system">
          <if-name>so-1/2/3.0</if-name>
          <if-admin-status>up</if-admin-status>
          <if-oper-status>down</if-oper-status>
        </link-failure>
      </notification>

                       Figure 25: Event notification

3.4.7.  Subscription State Notifications

   In addition to data plane notifications, a publisher may send
   subscription state notifications (defined in [subscribe]) to indicate
   to receivers that an event related to the subscription management has
   occurred.  Subscription state notifications cannot be filtered out.
   Next we exemplify them:






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3.4.7.1.  subscription-started and subscription-modified

   A subscription-started would look like:

     <notification
         xmlns=" urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
       <eventTime>2007-09-01T10:00:00Z</eventTime>
       <subscription-started
             xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0"/>
         <identifier>39</identifier>
         <stream>NETCONF</stream>
       </subscription-started/>
     </notification>


      Figure 26: subscription-started subscription state notification

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

3.4.7.2.  subscription-completed, subscription-resumed, and replay-
          complete

   A subscription-completed would look like:

     <notification
         xmlns=" urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
       <eventTime>2007-09-01T10:00:00Z</eventTime>
       <subscription-completed
             xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
         <identifier>39</identifier>
       </subscription-completed>
     </notification>

           Figure 27: subscription-completed notification in XML

   The equivalent using JSON encoding would be:














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      <notification
             xmlns=" urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
        <eventTime>2007-09-01T10:00:00Z</eventTime>
        <notification-contents-json>
             {
                "sn:subscription-completed": {
                "identifier" : 39
              }
        </notification-contents-json>
      </notification>

          Figure 28: subscription-completed notification in JSON

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

3.4.7.3.  subscription-terminated and subscription-suspended

   A subscription-terminated would look like:

     <notification
         xmlns=" urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
       <eventTime>2007-09-01T10:00:00Z</eventTime>
       <subscription-terminated
             xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push:1.0">
         <identifier>39</identifier>
         <error-id>error-insufficient-resources</error-id>
       </subscription-terminated>
     </notification>

     Figure 29: subscription-modified subscription state notification

   The above, and the subscription-suspended are virtually identical,
   with "subscription-terminated" simply being replaced by
   "subscription-suspended".

3.4.7.4.  Notification Message Flow Examples













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   +------------+                 +-----------+
   |   Client   |                 |   Server  |
   +------------+                 +-----------+
         |                              |
         |    Capability Exchange       |
         |<---------------------------->|
         |                              |
         |    Establish Subscription    |
         |<---------------------------->|
         |                              |
         |        Notification          |
         |<-----------------------------|
         |                              |
         |                              |
         |   Subscription Suspended     |
         |<-----------------------------|
         |                              |
         |                              |
         |                              |
         |    Subscription Resumed      |
         |<-----------------------------|
         |                              |
         |        Notification          |
         |<-----------------------------|
         |                              |

        Figure 30: subscription-suspended and resumed notifications
























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 +----------+                 +-----------+     +---------+  +---------+
 |  Client  |                 |   Server  |     | Rcver A |  | Rcver B |
 +----------+                 +-----------+     +---------+  +---------+
       |                            |                |            |
       |    Capability Exchange     |                |            |
       |<-------------------------->|                |            |
       |                            |                |            |
       |        Edit-config         |                |            |
       |--------------------------->|                |            |
       |       RPC Reply: OK        |                |            |
       |<---------------------------|                |            |
       |                            |  Subscription  |            |
       |                            |  Started       |            |
       |                            |--------------->|            |
       |                            |---------------------------->|
       |                            |                |            |
       |                            |  Notification  |            |
       |                            |--------------->|            |
       |                            |---------------------------->|
       |                            |                |            |
       |                            |  Subscription  |            |
       |                            |  Suspended     |            |
       |                            |--------------->|            |
       |                            |                |            |
       |                            |  Notification  |            |
       |                            |---------------------------->|
       |                            |                |            |
       |                            |  Subscription  |            |
       |                            |  Resumed       |            |
       |                            |--------------->|            |
       |                            |                |            |
       |                            |  Notification  |            |
       |                            |--------------->|            |
       |                            |---------------------------->|
       |                            |                |            |

        Figure 31: Suspended and resumed notifications for a single
                            configured receiver

4.  Interleave Capability

   The :interleave capability is originally defined in [RFC5277].  It is
   incorporated in this document with essentially the same semantics.
   That is, the NETCONF server MUST receive, process, and respond to
   NETCONF requests on a session with active notification subscriptions.

   The :interleave capability is identified by the following string:
   urn:ietf:params:netconf:capability:interleave:1.0



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   Note that subscription operations MUST be received, processed, and
   responded on a session with active notification subscriptions That
   mandatory requirement together with the :interleave capability
   permits a client performing all operations against a server using a
   single connection, allowing for better scalability with respect to
   the number of NETCONF sessions required to manage an entity.

5.  Security Considerations

   The <notification> elements are never sent before the transport layer
   and the NETCONF layer, including capabilities exchange, have been
   established and the manager has been identified and authenticated.

   A secure transport must be used and the server must ensure that the
   user has sufficient authorization to perform the function they are
   requesting against the specific subset of content involved.

   The contents of notifications, as well as the names of event streams,
   may contain sensitive information and care should be taken to ensure
   that they are viewed only by authorized users.  The NETCONF server
   MUST NOT include any content in a notification that the user is not
   authorized to view.

   If a malicious or buggy NETCONF client 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 suspect underlying NETCONF sessions.
   The server MAY also suspend or terminate a subset of the active
   subscriptions on the NETCONF session .

   Configured subscriptions from one or more publishers could be used to
   overwhelm a receiver, which perhaps doesn't even support
   subscriptions.  Clients that do not want pushed data need only
   terminate or refuse any transport sessions from the publisher.

   The NETCONF Authorization Control Model [RFC6536] SHOULD be used to
   control and restrict authorization of subscription configuration.
   This control models permits specifying per-user permissions to
   receive specific event notification types.  The permissions are
   specified as a set of access control rules.

6.  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, Kent Watsen, and Guangying Zheng.




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7.  References

7.1.  Normative References

   [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>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [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>.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536,
              DOI 10.17487/RFC6536, March 2012,
              <https://www.rfc-editor.org/info/rfc6536>.

   [RFC8071]  Watsen, K., "NETCONF Call Home and RESTCONF Call Home",
              RFC 8071, DOI 10.17487/RFC8071, February 2017,
              <https://www.rfc-editor.org/info/rfc8071>.

7.2.  Informative References

   [subscribe]
              Voit, Eric., Clemm, A., Gonzalez Prieto, A., Nilsen-
              Nygaard, E., and A. Tripathy, "Custom Subscription to
              Event Notifications", September 2017,
              <https://datatracker.ietf.org/doc/
              draft-ietf-netconf-subscribed-notifications/>.

   [yang-push]
              Clemm, A., Gonzalez Prieto, A., Voit, Eric., Tripathy, A.,
              Nilsen-Nygaard, E., Bierman, A., and B. Lengyel,
              "Subscribing to YANG datastore push updates", September
              2017, <https://datatracker.ietf.org/doc/
              draft-ietf-netconf-yang-push/>.




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Appendix A.  Open Items

   (To be removed by RFC editor prior to publication)

   o  Formal definition of: notification-contents-json, and
      incorporation of the subscription-id in the notifications.  It
      depends on the formal definition of the notification element

Appendix B.  Changes between revisions

   (To be removed by RFC editor prior to publication)

B.1.  v04 to v05

   o  Text presentation modifications throughout

   o  Modified examples to match the namespace, prefixes, and data node
      identifiers in [subscribe] and [yang-push]

   o  Modified examples to include <subscription-result> in all RPC
      responses

   o  Modified examples to include mandatory fields in [subscribe] and
      [yang-push]

B.2.  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.3.  v01 to v03

   o  Text simplifications throughout

   o  v02 had no meaningful changes

B.4.  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.



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   o  Added mapping between terminology in [yang-push] and [RFC6241]
      (the one followed in this document).

   o  Editorial improvements.

Authors' Addresses

   Alberto Gonzalez Prieto
   VMware

   Email: agonzalezpri@vmware.com


   Alexander Clemm
   Huawei

   Email: ludwig@clemm.org


   Eric Voit
   Cisco Systems

   Email: evoit@cisco.com


   Einar Nilsen-Nygaard
   Cisco Systems

   Email: einarnn@cisco.com


   Ambika Prasad Tripathy
   Cisco Systems

   Email: ambtripa@cisco.com
















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