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<rfc xmlns:xi="http://www.w3.org/2001/XInclude" category="std" ipr="trust200902" docName="draft-ietf-netconf-notification-capabilities-21"> number="9196" docName="draft-ietf-netconf-notification-capabilities-21" obsoletes="" updates="" submissionType="IETF" xml:lang="en" tocInclude="true" tocDepth="4" symRefs="true" sortRefs="true" version="3" consensus="true">

  <front>
    <title abbrev="System and abbrev="YANG System &amp; Notification Capabilities">
      YANG Modules describing Describing Capabilities for Systems and Datastore Update Notifications
    </title>
    <seriesInfo name="RFC" value="9196"/>
    <author initials="B." surname="Lengyel" fullname="Balazs Lengyel">
      <organization abbrev="Ericsson"> Ericsson </organization>
      <address>
        <postal>
          <street>Magyar Tudosok korutja 11</street>
          <city>1117 Budapest</city>
          <city>Budapest</city>
          <country>Hungary</country>
	  <code>1117</code>
        </postal>
        <email>balazs.lengyel@ericsson.com</email>
      </address>
    </author>
    <author fullname="Alexander Clemm" initials="A" surname="Clemm">
      <organization>Futurewei</organization>
      <address>
        <postal>
          <street>2330 Central Expressway</street>
          <city>Santa Clara, CA 95050</city>
          <country>USA</country> Clara</city>
	  <region>CA</region>
	  <code>95050</code>
          <country>United States of America</country>
        </postal>
        <email>ludwig@clemm.org</email>
      </address>
    </author>
    <author fullname="Benoit Claise" initials="B" surname="Claise">
      <organization>Huawei</organization>
      <address>
        <postal>
          <street></street>
          <city></city>
          <country></country>
          <street>George's Court Townsend Street</street>
          <city>Dublin 2</city>
          <country>Ireland</country>
        </postal>
        <email>benoit.claise@huawei.com</email>
      </address>
    </author>
    <date/>
    <date month="February" year="2022"/>
    <area>OPS</area>
    <workgroup>NETCONF</workgroup>

    <keyword>NMDA</keyword>
    <keyword>NETCONF</keyword>
    <keyword>RESTCONF</keyword>

    <abstract>
      <t>
        This document defines two YANG modules,"ietf-system-capabilities” modules, "ietf-system-capabilities" and
        "ietf-notification-capabilities”.
      </t><t>
        "ietf-notification-capabilities".
      </t>
      <t>
       The module "ietf-system-capabilities" provides a placeholder structure that
       can be used to discover YANG related YANG-related system capabilities for servers.
       The module can be used to report capability information from the server
       at run time runtime or at implementation time, time by making use of the YANG Instance Data
       File Format.
      </t><t> instance data file format.
      </t>
      <t>
       The module "ietf-notification-capabilities" augments "ietf-system-capabilities"
       to specify capabilities related to Subscription "Subscription to YANG Notifications
       for Datastore Updates. Updates" (RFC 8641).
      </t>
    </abstract>
  </front>
  <middle>
    <section anchor="intro" title="Introduction"> numbered="true" toc="default">
      <name>Introduction</name>
      <t>
        Servers and/or publishers often have capabilities, which can be represented by values describing that designate operational behavior, that need to be conveyed to clients, which is
        enabled by the clients. The YANG modules described that are defined in this document. document facilitate this.
      </t>
      <t>
        There is a need to publish this capability information as it is part of
        the API contract between the server and client. Examples include the maximum
        size of data that can be stored or transferred, information about counters (whether a node supports "on-change" telemetry), etc. Such capabilities are often dependent on a vendor's implementation or the available resources at deployment.
        Many such capabilities are specific to the complete system,
        individual YANG datastores <xref target="RFC8342"/>, target="RFC8342" format="default"/>, specific parts of the YANG
        schema, or even individual data nodes. It is a goal of this document to provide a
        common way of representing to represent such capabilities in a format that is:
        <list style="symbols">
        	<t>vendor independent</t>
        	<t>machine-readable</t>
        	<t>available
      </t>
      <ul spacing="normal">
        <li>vendor independent,</li>
        <li>machine readable, and</li>
        <li>available in an identical format both at implementation time and at run time.</t>
        </list>
      </t> runtime.</li>
      </ul>
      <t>
          Implementation-time information is needed by Network Management System
          (NMS) implementers.
          An NMS implementation that supports notifications needs the information
		  about a system's capability so it can send "on-change" notifications.
          If the information is not documented
          in a way that is readily available to the NMS designer, but only as instance data from
          the network node once it is deployed,
          the NMS implementation will be delayed, delayed because it has to wait for the
          network node to be ready. In addition, the assumption that all
          NMS implementers will
          have a correctly configured network node available from which to retrieve data from is an expensive proposition and may not always hold. (An NMS may need
          to be able to handle many dozens of network node types.)
          Often
          Often, a fully functional NMS is a requirement for introducing a new
          network node type
          into a network, so delaying NMS readiness effectively also delays the
          time at which a new network node type can be introduced into the network.
      </t>
      <t>
          Implementation-time information is needed by system integrators.
          When introducing a network node type into their network,
          operators often need to integrate the node type into their own
          management system. The NMS may have management functions that depend
          on "on-change" notifications. The network operators need to plan their
          management practices and NMS implementation before they decide to
          buy the specific network node type. Moreover, the decision to buy the node
          type sometimes depends on these management possibilities.
      </t>
      <t>
          Run-time
          Runtime capability information is needed:
          <list style="symbols">
            <t>for
      </t>
      <ul spacing="normal">
        <li>for any "purely model driven" model-driven" application, e.g., a NETCONF-browser. NETCONF browser.
              Such applications depend on reading models and capabilities at run time runtime
              to support all the publisher's available functionality.</t>
            <t>in functionality.</li>
        <li>in case the capability might change during run time runtime,
              e.g., due to licensing, HW constraints etc.</t>
            <t>to hardware constraints, etc.</li>
        <li>to check that that capability information provided earlier, at
              implementation time, is what the publisher has implemented.</t>
          </list>
        </t> implemented.</li>
      </ul>
      <section title="Terminology" anchor="terminology"> anchor="terminology" numbered="true" toc="default">
        <name>Terminology</name>
	        <t>
    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
           NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
           "MAY", "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
    NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
    "<bcp14>MAY</bcp14>", and "OPTIONAL" "<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as
    described in BCP 14 BCP&nbsp;14 <xref target="RFC2119"/> <xref target="RFC8174"/>
    when, and only when, they appear in all capitals, as shown here.
        </t>
        <t>The terms "YANG-Push", "on-change subscription" subscription", and "periodic
          subscription" are used as defined in <xref target="RFC8641"/>. target="RFC8641" format="default"/>.
        </t>
        <t>The terms "subscriber", "publisher" "publisher", and "receiver" are used as
          defined in <xref target="RFC8639"/>. target="RFC8639" format="default"/>.
        </t>
        <t>The term "server" is used as defined in <xref target="RFC8342"/>. target="RFC8342" format="default"/>.
        </t>
        <t>The terms "YANG instance data file format", "instance data", and
        	"instance data set" are used as defined in
          <xref target="I-D.ietf-netmod-yang-instance-file-format"/>. target="RFC9195"/>.
        </t>
        <t>In addition, this document defines the following terms:</t>
        <t>
          "Implementation-time information":
        <dl>
          <dt>Implementation-time information:</dt><dd> Information about the server's
          behavior that is made available during the implementation of the server,
          available from a source other than a running server.
        </t>
        <t>
          "Run-time information":
        </dd>
        <dt>
          Runtime information:</dt><dd> Information about the server's
          behavior that is available from the running server via management protocols
          such as NETCONF <xref target="RFC6241"/> target="RFC6241" format="default"/> or RESTCONF <xref target="RFC8040"/>.
        </t> target="RFC8040" format="default"/>.
        </dd></dl>
      </section>
    </section>
    <section anchor="capability-information" title="Providing numbered="true" toc="default">
      <name>Providing System Capability Information"> Information</name>
      <t>
        Capability information is represented by instance-data instance data based on one or
        more "capability defining "capability-defining YANG modules". This allows a user to discover
        capabilities both at implementation time and at run time. runtime.
      </t>
      <t>
        <list style="symbols">
          <t>For
      <dl spacing="normal">
        <dt>For the implementation-time use case: case:</dt><dd> Capabilities SHOULD <bcp14>SHOULD</bcp14> be provided by the
          implementer as YANG instance data files complying to with
          <xref target="I-D.ietf-netmod-yang-instance-file-format"/>. target="RFC9195"/>.
          When provided, the file MUST <bcp14>MUST</bcp14> already be available already at implementation time, time and retrievable in a way that does not depend
          on a live network node. E.g., download node, e.g., downloading from a product website.
</t>
          <t>For
</dd>
        <dt>For the run-time runtime use case: case:</dt><dd> Capabilities SHOULD <bcp14>SHOULD</bcp14> be available via
          NETCONF <xref target="RFC6241"/> target="RFC6241" format="default"/> or
          RESTCONF <xref target="RFC8040"/> target="RFC8040" format="default"/> from the live server (implementing
          the publisher) during run time. runtime.
          Implementations that support changing these capabilities at
          run time SHOULD
          runtime <bcp14>SHOULD</bcp14> support "on-change" notifications about the
          system-capabilities container.</t>
        </list>
      </t> container.</dd>
      </dl>
      <t>
        The module "ietf-system-capabilities" provides a placeholder structure to be used to specify any YANG related YANG-related system capability.
      </t><t>
      </t>
      <t>
        The module "ietf-notification-capabilities" is defined to allow a publisher to
        specify capabilities related to "Subscription to YANG Notifications for Datastore Updates" <xref target="RFC8641"/>, target="RFC8641" format="default"/>, also known as YANG-Push, augmenting "ietf-system-capabilities".
      </t><t>
      </t>
      <t>
        The YANG data models in this document conform to the Network
        Management Datastore Architecture (NMDA) defined in <xref target="RFC8342"/>. target="RFC8342" format="default"/>.
      </t>
    </section>
    <section anchor="Yang-Push-Capabilities" title="Providing numbered="true" toc="default">
      <name>Providing YANG-Push Notification Capabilities Information"> Information</name>
      <t>A specific case is the need to specify capabilities in the YANG-Push
        functionality. As defined in <xref target="RFC8641"/> target="RFC8641" format="default"/>, a publisher may allow
		subscribers to subscribe to updates from a datastore and will subsequently push
		such update notifications to the receiver. Notifications may be sent
          periodically or "on-change" "on change" (more or less immediately after each change).
      </t>
      <t>A publisher supporting YANG-Push has a number of capabilities defined in
          <xref target="RFC8641"/> target="RFC8641" format="default"/>
          that are often determined during the implementation of the publisher. These include:
          <list style="symbols">
            <t>Supported
      </t>
      <ul spacing="normal">
        <li>supported (reporting) periods for "periodic" subscriptions</t>
            <t>Maximum subscriptions.</li>
        <li>the maximum number of objects that can be sent in an update</t>
            <t>The update.</li>
        <li>the set of datastores or data nodes for which "periodic" notification is supported.</t>
          </list>
        </t> supported.</li>
      </ul>
      <t>Additional capabilities if the optional "on-change" feature is supported include:
          <list style="symbols">
            <t>Supported
      </t>
      <ul spacing="normal">
        <li>supported dampening periods for "on-change" subscriptions</t>
            <t>The subscriptions.</li>
        <li>the set of datastores or data nodes for which "on-change" notification is supported</t>
          </list>
        </t> supported.</li>
      </ul>
      <t>
          Publishers might have some capabilities (or limitations) to document.
          For document -- for example, how many update notifications and how many datastore node
          updates they can send out in a certain time-period. time period. Other publishers might
          not support "periodic" subscriptions to all datastores. In some cases, a publisher supporting "on-change" notifications will not
          be able to push updates for some object types "on-change". "on change". Reasons for
          this might be that the value of the datastore node changes frequently
          (e.g., in-octets in-octet counter), that small object changes are
          frequent and irrelevant to the receiver (e.g., a temperature gauge changing 0.1
          degrees within a predetermined and acceptable range), or
          that the implementation is not capable of on-change notification for
          a particular object. In all those cases, it will be important for
          subscriber applications to have a way to identify which the objects for which "on-change" notifications are supported and the objects for which ones they are not.
      </t>
      <t>
          Faced with the reality that support
          Support for "on-change" notification notifications does not
          mean that such notifications will be sent for any specific data node, as the ability to do so may not be supported for every data node. Therefore, subscriber/management applications can not cannot rely on the "on-change"
          functionality unless the subscriber has some means to identify which the objects for which "on-change" notifications are supported for. in fact supported. YANG data models are meant to be used as an
		  interface contract.
		  Without identification of the data nodes actually supporting "on-change", "on-change" notifications,
		  this contract would be incomplete.
      </t>
      <t>Clients of a server (and subscribers to a publisher, as subscribers are also clients) need a method to gather capability information.
      </t>
    </section>
    <section anchor="system_capabilities_model" title="System numbered="true" toc="default">
      <name>System Capabilities Model"> Model</name>
      <t>The module "ietf-system-capabilities" is defined to provide a
      	structure that can be used to discover (as a read-only operational state) any YANG related YANG-related system capability.</t>
      <t>This module itself does not contain any capabilities; it provides
        augmentation points for capabilities to be defined in subsequent YANG
        modules. The ietf-system-capabilies "ietf-system-capabilities" is used by other modules to augment in specific
        capability information.  Every set of such capabilities MUST <bcp14>MUST</bcp14> be
        wrapped in a container under the augment statement to cleanly
        separate different groups of capabilities. These "wrapper containers" SHALL <bcp14>SHALL</bcp14> be
        augmented in at /sysc:system-capabilities and /sysc:system-capabilities/sysc:datastore-capabilities/sysc:per-node-capabilities.</t>

	<t>
        Capability values can be specified on at the system level,
        at the datastore level (by selecting all nodes in the datastore) datastore),
        or for specific data nodes of a specific datastore
        (and their contained sub-trees). subtrees).

        Capability values specified for a specific datastore or
        node-set override values specified on at the system level.
      </t>
      <t>

      <t indent="3">
        Note: The solution is usable for both NMDA and non-NMDA systems.
        For non-NMDA servers servers, "config false" data is
        considered as if it were part of the running datastore.
      </t>
      <section title="Tree Diagram"> numbered="true" toc="default">
        <name>Tree Diagram</name>
        <t>
          The following tree diagram <xref target="RFC8340"/> target="RFC8340" format="default"/>
          provides an overview of the data model.
        </t>
        <t>
            <figure>
              <artwork><![CDATA[

        <sourcecode name="" type="yangtree"><![CDATA[
module: ietf-system-capabilities
  +--ro system-capabilities
     +--ro datastore-capabilities* [datastore]
        +--ro datastore       -> /yanglib:yang-library/datastore/name
        +--ro per-node-capabilities* []
           +--ro (node-selection)?
              +--:(node-selector)
                 +--ro node-selector?   nacm:node-instance-identifier
]]></artwork>
            </figure>
        </t>
]]></sourcecode>
      </section>
      <section title="YANG Module" anchor="ietf-system-capabilities.yang"> anchor="ietf-system-capabilities.yang" numbered="true" toc="default">
        <name>YANG Module</name>
        <t>This YANG module imports typedefs from <xref target="RFC8341"/> target="RFC8341" format="default"/> and
          a reference path from <xref target="RFC8525"/>. target="RFC8525" format="default"/>.
        </t>
          <figure>
            <artwork><![CDATA[
<CODE BEGINS> file "ietf-system-capabilities@2021-10-12.yang"

<sourcecode name="ietf-system-capabilities@2022-01-21.yang" type="yang" markers="true"><![CDATA[
module ietf-system-capabilities {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-system-capabilities";
  prefix sysc;

  import ietf-netconf-acm {
    prefix nacm;
    reference
      "RFC 8341: Network Configuration Access Control Model";
  }
  import ietf-yang-library {
    prefix yanglib;
    description
      "This module requires ietf-yang-library to be implemented.
       Revision 2019-01-04 or a revision derived from it
       is REQUIRED.";
    reference
      "RFC8525: YANG Library";
  }

  organization
    "IETF NETCONF (Network Configuration) Working Group";
  contact
    "WG Web:   <https://datatracker.ietf.org/wg/netconf/>
     WG List:  <mailto:netconf@ietf.org>

     Editor:   Balazs Lengyel
               <mailto:balazs.lengyel@ericsson.com>";
  description
    "This module specifies a structure to specify system
     capabilities for a server or a publisher.  System capabilities
     may include capabilities of a NETCONF or RESTCONF server or a
     notification publisher.

     This module does not contain any specific capabilities, capabilities; it only
     provides a structure where containers containing the actual
     capabilities are augmented in.

     Capability values can be specified on at the system level, at the
     datastore level (by selecting all nodes in the datastore) datastore), or
     for specific data nodes of a specific datastore (and their
     contained sub-trees). subtrees).
     Capability values specified for a specific datastore or
     node-set override values specified on the system/publisher
     level.

     The same grouping MUST be used to define hierarchical
     capabilities supported both at the system level and datastore/data node at the
     datastore/data-node level.

     To find a capability value for a specific data node in a
     specific datastore datastore, the user SHALL:

     1) search for a datastore-capabilities list entry for
     the specific datastore.  When stating a specific capability, the
     relative path for any specific capability must be the same
     under the system-capabilities container and under the
     per-node-capabilities list.

     2) If the datastore entry is found within that entry, process
     all per-node-capabilities entries in the order they appear in
     the list.  The first entry that specifies the specific
     capability and has a node-selector selecting the specific data
     node defines the capability value.

     3) If the capability value is not found above and the specific
     capability is specified under the system-capabilities container
     (outside the datastore-capabilities list), this value shall be
     used.

     4) If no values are found in the previous steps, the
     system/publisher is not capable of providing a value.  Possible
     reasons are: are that it is unknown, the capability is changing for
     some reason, there is no specified limit, etc.  In this case case,
     the system's behavior is unspecified.

     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 (RFC 2119)
     (RFC 8174) when, and only when, they appear in all
     capitals, as shown here.

     Copyright (c) 2021 2022 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject to
     the license terms contained in, the Simplified Revised BSD License set
     forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (https://trustee.ietf.org/license-info).

     This version of this YANG module is part of RFC XXXX
     (https://www.rfc-editor.org/info/rfcXXXX); 9196
     (https://www.rfc-editor.org/info/rfc9196); see the RFC itself
     for full legal notices.";

  // RFC Ed.: replace XXXX with actual RFC number and remove this
  // note.

  revision 2021-10-12 2022-01-21 {
    description
      "Initial version
       NOTE TO RFC EDITOR:
       (1)Please replace the above revision date to
         the date of RFC publication when published.
       (2) Please replace the date in the file name
         (ietf-system-capabilities@2021-10-12.yang)
         to the date of RFC publication.
       (3) Please replace the following reference
         with RFC number when published
         (i.e. RFC xxxx)."; version";
    reference
      "RFC XXXX: 9196: YANG Modules describing Describing Capabilities for Systems
       and Datastore Update Notifications";
  }

  container system-capabilities {
    config false;
    description
      "System capabilities.
       Capability values specified here at the system level
       are valid for all datastores and are used when the
       capability is not specified on at the datastore level
       or for specific data nodes.";
    /*
     * "Augmentation point for system level system-level capabilities."
     */
    list datastore-capabilities {
      key "datastore";
      description
        "Capabilities values per datastore.

         For non-NMDA servers/publishers servers/publishers, 'config false' data is
         considered as if it was were part of the running datastore.";
      leaf datastore {
        type leafref {
          path
            "/yanglib:yang-library/yanglib:datastore/yanglib:name";
        }
        description
          "The datastore for which capabilities are defined.
           Only one specific datastore can be specified specified,
           e.g., ds:conventional, which ds:conventional must not be used, as it
           represents a set of configuration datastores, must not be used."; datastores.";
      }
      list per-node-capabilities {
        description
          "Each list entry specifies capabilities for the selected
           data nodes.  The same capabilities apply for to the data nodes
           in the subtree below the selected nodes.

           The system SHALL order the entries according to their
           precedence. The order of the entries MUST NOT change
           unless the underlying capabilities also change.

           Note that the longest patch matching can be achieved
           by ordering more specific matches before less
           specific ones.";
        choice node-selection {
          description
            "A method to select some or all nodes within a
             datastore.";
          leaf node-selector {
            type nacm:node-instance-identifier;
            description
              "Selects the data nodes for which capabilities are
               specified. The special value '/' denotes all data
               nodes in the datastore, consistent with the path
               leaf node on page 41 of [RFC8341].";
            reference
              "RFC 8341: Network Configuration Access Control Model";
          }
        }
        /*
         * "Augmentation point for datastore datastore- or data node level data-node-level
         * capabilities."
         */
      }
    }
  }
}
            ]]></artwork>
          </figure>
        <t>&lt;CODE ENDS></t>

]]></sourcecode>

      </section>
    </section>
    <section anchor="notification-capabilities_model" title="Notification numbered="true" toc="default">
      <name>Notification Capabilities Model"> Model</name>
      <t>
        The YANG module "ietf-notification-capabilities" provides YANG-Push information related capability information. to the YANG-Push capability.
      </t>
      <section title="Tree Diagram"> numbered="true" toc="default">
        <name>Tree Diagram</name>
        <t>
          The following tree diagram <xref target="RFC8340"/> target="RFC8340" format="default"/>
          provides an overview of the data model.
        </t>
        <t>
            <figure>
              <artwork><![CDATA[
        <sourcecode name="" type="yangtree"><![CDATA[
module: ietf-notification-capabilities
  augment /sysc:system-capabilities:
    +--ro subscription-capabilities
       +--ro max-nodes-per-update?               uint32
       +--ro periodic-notifications-supported?   notification-support
       +--ro (update-period)?
       |  +--:(minimum-update-period)
       |  |  +--ro minimum-update-period?        uint32
       |  +--:(supported-update-period)
       |     +--ro supported-update-period*      uint32
       +--ro on-change-supported?                notification-support
       |       {yp:on-change}?
       +--ro minimum-dampening-period?           uint32
       |       {yp:on-change}?
       +--ro supported-excluded-change-type*     union
               {yp:on-change}?
  augment /sysc:system-capabilities/sysc:datastore-capabilities
            /sysc:per-node-capabilities:
    +--ro subscription-capabilities
       +--ro max-nodes-per-update?               uint32
       +--ro periodic-notifications-supported?   notification-support
       +--ro (update-period)?
       |  +--:(minimum-update-period)
       |  |  +--ro minimum-update-period?        uint32
       |  +--:(supported-update-period)
       |     +--ro supported-update-period*      uint32
       +--ro on-change-supported?                notification-support
       |       {yp:on-change}?
       +--ro minimum-dampening-period?           uint32
       |       {yp:on-change}?
       +--ro supported-excluded-change-type*     union
               {yp:on-change}?
]]></artwork>
            </figure>
        </t>
]]></sourcecode>
      </section>
      <section title="YANG Module" anchor="ietf-notification-capabilities.yang"> anchor="ietf-notification-capabilities.yang" numbered="true" toc="default">
        <name>YANG Module</name>
        <t>This YANG module imports a feature and typedefs from <xref target="RFC8641"/> target="RFC8641" format="default"/>
        and also imports the "ietf-system-capabilities" specified in this document.
        </t>
          <figure>
            <artwork><![CDATA[
<CODE BEGINS> file "ietf-notification-capabilities@2021-10-12.yang"

        <sourcecode name="ietf-notification-capabilities@2022-01-21.yang" type="yang" markers="true"><![CDATA[
module ietf-notification-capabilities {
  yang-version 1.1;
  namespace
    "urn:ietf:params:xml:ns:yang:ietf-notification-capabilities";
  prefix notc;

  import ietf-yang-push {
    prefix yp;
    description
      "This module requires ietf-yang-push to be implemented.";
    reference
      "RFC 8641: Subscription to YANG Notifications for
       Datastore Updates";
  }
  import ietf-system-capabilities {
    prefix sysc;
    description
      "This module requires ietf-system-capabilities to be
       implemented.";
    reference
      "RFC XXXX: 9196: YANG Modules describing Describing Capabilities for Systems
       and Datastore Update Notifications";
  }

  // RFC Ed.: replace the above XXXX with actual RFC number
  // and remove this note.

  organization
    "IETF NETCONF (Network Configuration) Working Group";
  contact
    "WG Web:   <https://datatracker.ietf.org/wg/netconf/>
     WG List:  <mailto:netconf@ietf.org>

     Editor:   Balazs Lengyel
               <mailto:balazs.lengyel@ericsson.com>";
  description
    "This module specifies YANG-Push [RFC 8641] related publisher
     capabilities. capabilities related to
     YANG-Push (RFC 8641).

     The module contains:

     - a specification of which the data nodes that support 'on-change' or
     'periodic' notifications.

     - capabilities related to the throughput of notification data
     that the publisher can support.  (Note that for a specific
     subscription, the publisher MAY allow only longer periods
     or smaller updates depending on, e.g., actual load conditions.)

     Capability values can be specified on at the system/publisher
     level, at the datastore level level, or for specific data nodes of
     a specific datastore (and their contained sub-trees), subtrees), as defined
     in the ietf-system-capabilities module.

     If different data nodes covered by a single subscription
     have different values for a specific capability, then using
     values that are only acceptable for some of these data nodes,
     but not for others, may result in the rejection of the
     subscription.

     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 (RFC 2119)
     (RFC 8174) when, and only when, they appear in all
     capitals, as shown here.

     Copyright (c) 2021 2022 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject to
     the license terms contained in, the Simplified Revised BSD License set
     forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (https://trustee.ietf.org/license-info).

     This version of this YANG module is part of RFC XXXX
     (https://www.rfc-editor.org/info/rfcXXXX); 9196
     (https://www.rfc-editor.org/info/rfc9196); see the RFC itself
     for full legal notices.";

  // RFC Ed.: replace XXXX with actual RFC number and remove this
  // note.

  revision 2021-10-12 2022-01-21 {
    description
      "Initial version";
    reference
      "RFC XXXX: 9196: YANG Modules describing Describing Capabilities for Systems
       and Datastore Update Notifications";
  }

  // RFC Ed.: replace XXXX with actual RFC number and remove this
  // note.

  grouping subscription-capabilities {
    description
      "Capabilities related to YANG-Push subscriptions
       and notifications";
    container subscription-capabilities {
      description
        "Capabilities related to YANG-Push subscriptions
         and notifications";
      typedef notification-support {
        type bits {
          bit config-changes {
            description
              "The publisher is capable of sending
               notifications for 'config true' nodes for the
               relevant scope and subscription type.";
          }
          bit state-changes {
            description
              "The publisher is capable of sending
               notifications for 'config false' nodes for the
               relevant scope and subscription type.";
          }
        }
        description
          "Type for defining whether 'on-change' or
           'periodic' notifications are supported for all data nodes,
           'config false' data nodes, 'config true' data nodes, or
           no data nodes.

           If the bit

           The bits config-changes or state-changes is have no effect
           when they are set for a datastore, datastore or for a set of nodes
           that does not contain nodes with the indicated config value, this has no
           effect,
           value.  In those cases, the effect is the same as if no
           support was declared. E.g.  One example of this is indicating
           support for state-changes for a candidate datastore that
           has no effect.";
      }

      leaf max-nodes-per-update {
        type uint32 {
          range "1..max";
        }
        description
          "Maximum number of data nodes that can be sent
           in an update. The publisher MAY support more data nodes, nodes
           but SHOULD support at least this number.

           May be used to avoid the 'update-too-big' error
           during subscription.";
        reference
          "RFC 8641: Subscription to YANG Notifications for
           Datastore Updates, the 'update-too-big' error/identity";
      }
      leaf periodic-notifications-supported {
        type notification-support;
        description
          "Specifies whether the publisher is capable of
           sending 'periodic' notifications for the selected
           data nodes nodes, including any subtrees that may exist
           below them.";
        reference
          "RFC 8641: Subscription to YANG Notifications for
           Datastore Updates, 'periodic' subscription concept";
      }
      choice update-period {
        description
          "Supported update period value or values for
           'periodic' subscriptions.";
        leaf minimum-update-period {
          type uint32;
          units "centiseconds";
          description
            "Indicates the minimal update period that is
             supported for a 'periodic' subscription.

             A subscription request to the selected data nodes with
             a smaller period than what this leaf specifies is
             likely to result in a 'period-unsupported' error.";
          reference
            "RFC 8641: Subscription to YANG Notifications for
             Datastore Updates, the period leaf in the ietf-yang-push
             YANG module";
        }
        leaf-list supported-update-period {
          type uint32;
          units "centiseconds";
          description
            "Supported update period values for a 'periodic'
             subscription.

             A subscription request to the selected data nodes with a
             period not included in the leaf-list will result in a
             'period-unsupported' error.";
          reference
            "RFC 8641: Subscription to YANG Notifications for
             Datastore Updates, the period leaf in the ietf-yang-push
             YANG module";
        }
      }
      leaf on-change-supported {
        if-feature "yp:on-change";
        type notification-support;
        description
          "Specifies whether the publisher is capable of
           sending 'on-change' notifications for the selected
           data nodes and the subtree below them.";
        reference
          "RFC 8641: Subscription to YANG Notifications for Datastore
           Updates, on-change concept";
      }
      leaf minimum-dampening-period {
        if-feature "yp:on-change";
        type uint32;
        units "centiseconds";
        description
          "The minimum dampening-period dampening period supported for 'on-change'
           subscriptions for the selected data nodes.

           If this value is present and greater than zero,
           that implies dampening is mandatory.";
        reference
          "RFC 8641: Subscription to YANG Notifications for
           Datastore Updates, the dampening-period leaf in the
           ietf-yang-push YANG module";
      }
      leaf-list supported-excluded-change-type {
        if-feature "yp:on-change";
        type union {
          type enumeration {
            enum none {
              value -2;
              description
                "None of the change types can be excluded.";
            }
            enum all {
              value -1;
              description
                "Any combination of change types can be excluded.";
            }
          }
          type yp:change-type;
        }
        description
          "The change types that can be excluded in
           YANG-Push subscriptions for the selected data nodes.";
        reference
          "RFC 8641: Subscription to YANG Notifications for Datastore
           Updates, the change-type typedef in the ietf-yang-push
           YANG module";
      }
    }
  }

  augment "/sysc:system-capabilities" {
    description
      "Add system level capabilities";
    uses subscription-capabilities {
      refine
        "subscription-capabilities/supported-excluded-change-type" {
        default "none";
      }
    }
  }

  augment "/sysc:system-capabilities/sysc:datastore-capabilities"
        + "/sysc:per-node-capabilities" {
    description
      "Add datastore and node level node-level capabilities";
    uses subscription-capabilities {
      refine
        "subscription-capabilities/supported-excluded-change-type" {
        default "none";
      }
    }
  }
}
            ]]></artwork>
          </figure>
            ]]></sourcecode>
        <t>&lt;CODE ENDS></t> ENDS&gt;</t>
      </section>
    </section>
    <section anchor="security" title="Security Considerations"> numbered="true" toc="default">
      <name>Security Considerations</name>
      <t>
         The YANG modules specified in this document define a schema for data
         that is designed to be accessed via network management protocols such
         as NETCONF <xref target="RFC6241"/> target="RFC6241" format="default"/> or RESTCONF <xref target="RFC8040"/> target="RFC8040" format="default"/>
         or as YANG instance data.
		 The lowest NETCONF layer is the secure transport layer, and the
		 mandatory-to-implement secure transport is Secure Shell (SSH)
		 <xref target="RFC6242"/>. target="RFC6242" format="default"/>. The lowest RESTCONF layer is HTTPS, and
		 the mandatory-to-implement secure transport is TLS <xref target="RFC8446"/>. target="RFC8446" format="default"/>.
      </t>
      <t>
         The Network Configuration Access Control Model (NACM) [RFC8341] <xref target="RFC8341"/>
         provides the means to restrict access for particular NETCONF or
         RESTCONF users to a preconfigured subset of all available NETCONF or
         RESTCONF protocol operations and content.
      </t>

      <t>
         This document outlines a framework for conveying system capability
		 information that is inherently flexible and extensible.  While the full
		 set of use cases is not known now, they may range as wide as conveying
		 the minimum update period for periodic subscription updates and what
		 protocols might be used for such notifications.  Knowledge of this type
		 of value might, for example, allow an attacker to gain insight into how
		 long unauthorized configuration changes might be active prior to detection, detection
		 and what communications channels might be disrupted to extend the period
		 of non-detection.  Documents adding additional capabilities via augmenting
		 this module are encouraged to document the security considerations of the

		 new YANG nodes, according to the guidance in BCP 216. 216 <xref target="RFC8407"/>.
      </t>
      <t> All protocol-accessible data nodes in augmented modules are read-only
	    and cannot be modified. The data in these modules is not security sensitive. Access control may be configured, configured to avoid exposing the any read-only data. data that is defined by the augmenting module
  documentation as being security sensitive.
      </t>
      <t>When that data is in file format, the data should be protected against
      modification or unauthorized access using normal file handling file-handling mechanisms.
		The data in file format also inherits all the security considerations of
		<xref target="I-D.ietf-netmod-yang-instance-file-format"/> target="RFC9195"/>, which has includes additional
		considerations about read protections; protections and distinguishes between data at
		rest and in motion.
      </t>
    </section>
    <section anchor="iana" title="IANA Considerations"> numbered="true" toc="default">
      <name>IANA Considerations</name>
      <section title="The numbered="true" toc="default">
        <name>The IETF XML Registry"> Registry</name>
        <t>This document registers two the following URIs in the IETF "IETF XML
          registry
          Registry" <xref target="RFC3688"/>. Following the format in
          <xref target="RFC3688"/>, the following registrations are
          requested:</t>
        <t><figure><artwork>
   URI: urn:ietf:params:xml:ns:yang:ietf-system-capabilities
   Registrant Contact: The NETCONF WG of the IETF.
   XML: target="RFC3688" format="default"/>:</t>
<dl spacing="compact">
   <dt>URI:</dt><dd> urn:ietf:params:xml:ns:yang:ietf-system-capabilities</dd>
   <dt>Registrant Contact:</dt><dd>The IESG.</dd>
   <dt>XML:</dt><dd> N/A, the requested URI is an XML namespace.
        </artwork></figure></t>
        <t><figure><artwork>
   URI: urn:ietf:params:xml:ns:yang:ietf-notification-capabilities
   Registrant Contact: The NETCONF WG of the IETF.
   XML: namespace.</dd>
</dl>
<dl spacing="compact">
   <dt>URI:</dt><dd> urn:ietf:params:xml:ns:yang:ietf-notification-capabilities</dd>
   <dt>Registrant Contact:</dt><dd>The IESG.</dd>
   <dt>XML:</dt><dd> N/A, the requested URI is an XML namespace.
        </artwork></figure></t> namespace.</dd>
</dl>
      </section>
      <section title="The numbered="true" toc="default">
        <name>The YANG Module Names Registry"> Registry</name>
        <t>This document registers two the following YANG modules in the
          YANG
          "YANG Module Names Names" registry <xref target="RFC6020"/>.
          Following the format in <xref target="RFC6020"/>, the
          following registrations are requested:</t>
        <t><figure><artwork>
   name:       ietf-system-capabilities
   namespace:  urn:ietf:params:xml:ns:yang:ietf-system-capabilities
   prefix:     sysc
   reference: target="RFC6020" format="default"/>:</t>
<dl spacing="compact">
   <dt>name:</dt><dd>       ietf-system-capabilities</dd>
   <dt>namespace:</dt><dd>  urn:ietf:params:xml:ns:yang:ietf-system-capabilities</dd>
   <dt>prefix:</dt><dd>     sysc</dd>
   <dt>reference:</dt><dd>  RFC XXXX
        </artwork></figure></t>
        <t><figure><artwork>
   name:       ietf-notification-capabilities
   namespace:
        urn:ietf:params:xml:ns:yang:ietf-notification-capabilities
   prefix:     notc
   reference: 9196</dd>
</dl>
<dl spacing="compact">
   <dt>name:</dt><dd>       ietf-notification-capabilities</dd>
   <dt>namespace:</dt><dd>
        urn:ietf:params:xml:ns:yang:ietf-notification-capabilities</dd>
   <dt>prefix:</dt><dd>     notc</dd>
   <dt>reference:</dt><dd>  RFC XXXX
        </artwork></figure></t>
      </section> 9196</dd>
</dl>
      </section>
    <section title="Acknowledgments">
        <t>For their valuable comments, discussions, and feedback, we wish to
        acknowledge Andy Bierman, Juergen Schoenwaelder, Rob Wilton, Kent Watsen,
        Eric Voit, Joe Clarke, Martin Bjorklund, Ladislav Lhotka, Qin Wu,
        Mahesh Jethanandani, Ran Tao, Reshad Rahman and other members of the Netmod WG.</t>
    </section>
  </middle>
  <back>
    <references title="Normative References">
      <?rfc include='reference.I-D.ietf-netmod-yang-instance-file-format'?>
      <?rfc include='reference.RFC.2119'?>
      <?rfc include='reference.RFC.3688'?>
      <?rfc include='reference.RFC.6020'?>
      <?rfc include='reference.RFC.8174'?>
      <?rfc include="reference.RFC.8341"?>
      <?rfc include="reference.RFC.8342"?>
      <?rfc include="reference.RFC.8525"?>
      <?rfc include='reference.RFC.8639'?>
      <?rfc include='reference.RFC.8641'?>
    <references>
      <name>References</name>
      <references>
        <name>Normative References</name>

<reference anchor="RFC9195" target="https://www.rfc-editor.org/info/rfc9195">
<front>
<title>A File Format for YANG Instance Data</title>
<author initials='B' surname='Lengyel' fullname='Balazs Lengyel'>
<organization />
</author>
<author initials='B' surname='Claise' fullname='Benoit Claise'>
<organization />
</author>
<date year='2022' month='February' />
</front>
<seriesInfo name="RFC" value="9195"/>
<seriesInfo name="DOI" value="10.17487/RFC9195"/>
</reference>

        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.3688.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6020.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8341.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8342.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8525.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8639.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8641.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6241.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6242.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8040.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8446.xml"/>

      </references>
      <references>
        <name>Informative References</name>

        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8407.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8340.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8792.xml"/>
      </references>
    <references title="Informative References">
      <?rfc include='reference.RFC.6241'?>
      <?rfc include='reference.RFC.6242'?>
      <?rfc include="reference.RFC.8040"?>
      <?rfc include="reference.RFC.8340"?>
      <?rfc include="reference.RFC.8446"?>
      <?rfc include="reference.RFC.8792"?>
    </references>
    <?rfc needLines="100"?>
    <section title="Instance data example #1"> numbered="true" toc="default">
      <name>Instance Data Example #1</name>
      <t>The following examples use artwork folding
           <xref target="RFC8792"/> target="RFC8792" format="default"/> for better formatting.</t>
      <t>
        The following instance data example describes the notification
        capabilities of a hypothetical "acme-router". The router implements
        the running and operational datastores.
        Every change can be reported "on-change" from the running datastore,
        but only "config false" nodes and some "config false" data can be reported on-change from the
        operational datastore.
        Interface statistics are not reported "on-change", "on-change"; only two important counters. counters are.
        Datastore subscription capabilities are not reported "on-change", as they
        never change on the acme-router during run time. runtime.
      </t>
      <figure align="center" anchor="acme-router-notification-capabilities"
          title="Notification anchor="acme-router-notification-capabilities">
        <name>Notification Capabilities with data node specific settings">
          <artwork align="left" name="acme-router-notification-capabilities.xml"><![CDATA[ Settings Specific to the Data Node</name>
        <sourcecode name="acme-router-notification-capabilities.xml" type="xml"><![CDATA[
========== NOTE: '\' line wrapping per RFC 8792) ===========

<?xml version="1.0" encoding="UTF-8"?>
<instance-data-set xmlns=\
    "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data">
  <name>acme-router-notification-capabilities</name>
  <content-schema>
    <module>ietf-system-capabilities@2021-10-12</module>
    <module>ietf-notification-capabilities@2021-10-12</module>
    <module>ietf-system-capabilities@2022-01-21</module>
    <module>ietf-notification-capabilities@2022-01-21</module>
  </content-schema>
  <description>Defines the notification capabilities of an
    acme-router. The router only has running and operational
    datastores. Every change can be reported on-change from the
    running datastore, but only "config false" nodes and some
    "config false" data can be reported on-change from the
    operational datastore. Statistics
    are not reported on-change except for two important counters,
    where a small dampening period is mandated.
  </description>
  <content-data>
    <system-capabilities \
     xmlns="urn:ietf:params:xml:ns:yang:ietf-system-capabilities" \
     xmlns:notc=\
       "urn:ietf:params:xml:ns:yang:ietf-notification-capabilities" \
     xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
     <notc:subscription-capabilities>
      <notc:minimum-update-period>500</notc:minimum-update-period>
      <notc:max-nodes-per-update>2000</notc:max-nodes-per-update>
      <notc:minimum-dampening-period>100</notc:minimum-dampening-period>
      <notc:minimum-dampening-period>\
         100\
      </notc:minimum-dampening-period>
      <notc:periodic-notifications-supported>\
         config-changes state-changes\
      </notc:periodic-notifications-supported>
      <notc:on-change-supported>\
         config-changes state-changes\
      </notc:on-change-supported>
      <notc:supported-excluded-change-type>\
         all\
      </notc:supported-excluded-change-type>
     </notc:subscription-capabilities>
      <datastore-capabilities>
        <datastore>ds:operational</datastore>
        <per-node-capabilities>
          <node-selector>\
              /if:interfaces/if:interface[if:name='lo']\
          </node-selector>
          <notc:subscription-capabilities>
            <notc:on-change-supported/>
            <notc:periodic-notifications-supported/>
          </notc:subscription-capabilities>
        </per-node-capabilities>
        <per-node-capabilities>
          <node-selector>\
              /if:interfaces/if:interface/if:statistics/if:in-octets\
          </node-selector>
          <notc:subscription-capabilities>
            <notc:minimum-dampening-period>10
              </notc:minimum-dampening-period>
            <notc:on-change-supported>\
              state-changes\
            </notc:on-change-supported>
          </notc:subscription-capabilities>
        </per-node-capabilities>
        <per-node-capabilities>
          <node-selector>\
          /if:interfaces/if:interface/if:statistics/if:out-octets\
          </node-selector>
          <notc:subscription-capabilities>
            <notc:minimum-dampening-period>10
              </notc:minimum-dampening-period>
            <notc:on-change-supported>\
              state-changes\
            </notc:on-change-supported>
          </notc:subscription-capabilities>
        </per-node-capabilities>
        <per-node-capabilities>
          <node-selector>\
              /if:interfaces/if:interface/if:statistics\
          </node-selector>
          <notc:subscription-capabilities>
            <notc:on-change-supported/>
          </notc:subscription-capabilities>
        </per-node-capabilities>
      </datastore-capabilities>
    </system-capabilities>
  </content-data>
</instance-data-set>
          ]]></artwork>
          ]]></sourcecode>
      </figure>
      </t>
    </section>
    <section title="Instance data example #2"> numbered="true" toc="default">
      <name>Instance Data Example #2</name>
      <t>The following examples use artwork folding
        <xref target="RFC8792"/> target="RFC8792" format="default"/> for better formatting.</t>
      <t>
        The following instance data example describes the notification
        capabilities of a hypothetical "acme-switch". The switch implements
        the running, candidate candidate, and operational
        datastores.

	Every change can be reported "on-change" from the
         running datastore, nothing can be reported on-change from the candidate datastore datastore, and all
         "config false" data can be reported on-change from the operational datastore.
        "periodic"
        "Periodic" subscriptions are supported for running and
        operational,
        operational but not for candidate datastores.
      </t>
      <figure align="center" anchor="acme-switch-notification-capabilities" title="Notification anchor="acme-switch-notification-capabilities">
        <name>Notification Capabilities with datastore level settings">
          <artwork align="left" name="acme-switch-notification-capabilities.xml"><![CDATA[ Datastore-Level Settings</name>

        <sourcecode name="acme-switch-notification-capabilities.xml" type="xml"><![CDATA[
========== NOTE: '\' line wrapping per RFC 8792) ===========

<?xml version="1.0" encoding="UTF-8"?>
<instance-data-set xmlns=\
    "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data">
  <name>acme-switch-notification-capabilities</name>
  <content-schema>
    <module>ietf-system-capabilities@2021-10-12</module>
    <module>ietf-notification-capabilities@2021-10-12</module>
    <module>ietf-system-capabilities@2022-01-21</module>
    <module>ietf-notification-capabilities@2022-01-21</module>
  </content-schema>
  <description>Notification capabilities of acme-switch.
    Acme-switch implements the running, candidate candidate, and operational
    datastores. Every change can be reported on-change from the
    running datastore, nothing from the candidate datastore and
    all "config false" data from the operational datastore. Periodic
    subscriptions are supported for running and operational, but not
    for candidate datastore.
  </description>
  <content-data>
    <system-capabilities \
     xmlns="urn:ietf:params:xml:ns:yang:ietf-system-capabilities" \
     xmlns:notc=\
       "urn:ietf:params:xml:ns:yang:ietf-notification-capabilities" \
     xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
     <notc:subscription-capabilities>
      <notc:minimum-update-period>500</notc:minimum-update-period>
      <notc:max-nodes-per-update>2000</notc:max-nodes-per-update>
      <notc:minimum-dampening-period>100</notc:minimum-dampening-period>
      <notc:minimum-dampening-period>\
        100\
      </notc:minimum-dampening-period>
      <notc:periodic-notifications-supported>\
        config-changes state-changes\
      </notc:periodic-notifications-supported>
     </notc:subscription-capabilities>
     <datastore-capabilities>
       <datastore>ds:operational</datastore>
       <per-node-capabilities>
         <node-selector>/</node-selector>
         <notc:subscription-capabilities>
           <notc:on-change-supported>\
             state-changes\
           </notc:on-change-supported>
         </notc:subscription-capabilities>
       </per-node-capabilities>
     </datastore-capabilities>
     <datastore-capabilities>
       <datastore>ds:candidate</datastore>
       <per-node-capabilities>
         <node-selector>/</node-selector>
         <notc:subscription-capabilities>
           <notc:on-change-supported/>
           <notc:periodic-notifications-supported/>
         </notc:subscription-capabilities>
       </per-node-capabilities>
     </datastore-capabilities>
     <datastore-capabilities>
      <datastore>ds:running</datastore>
       <per-node-capabilities>
         <node-selector>/</node-selector>
         <notc:subscription-capabilities>
           <notc:on-change-supported>\
             config-changes\
           </notc:on-change-supported>
         </notc:subscription-capabilities>
       </per-node-capabilities>
     </datastore-capabilities>
    </system-capabilities>
  </content-data>
</instance-data-set>
          ]]></artwork>
          ]]></sourcecode>
      </figure>
      </t>
    </section>
    <section title="Changes between revisions">
      <t>   Note to RFC Editor (To be removed by RFC Editor)</t>
      <t>v20 - v21
        <list style="symbols">
          <t>IESG review</t>
        </list>
      </t>
      <t>v19 - v20
        <list style="symbols">
          <t>IESG review</t>
        </list>
      </t>
      <t>v18 - v19
        <list style="symbols">
          <t>IESG review</t>
        </list>
      </t>
      <t>v17 - v18
        <list style="symbols">
          <t>IESG review</t>
        </list>
      </t>
      <t>v16 - v17
        <list style="symbols">
          <t>AD review comments addressed</t>
        </list>
      </t>
      <t>v15 - v16
        <list style="symbols">
          <t>Two editorial comments from document shepherd</t>
        </list>
      </t>
      <t>v14 - v15
        <list style="symbols">
          <t>Address the last comments from document shepherd</t>
        </list>
      </t>
      <t>v13 - v14
        <list style="symbols">
          <t>Updated according to sheperds review</t>
          <t>Added to import, which imported modules need to be implemented.</t>
          <t>Added notes to the RFC editor</t>
          <t>Re-arrange the sections, for a better reading flow</t>
          <t>Many editorial changes</t>
          <t>Replace YANG module prefix</t>
        </list>
      </t>
      <t>v12 - v13
        <list style="symbols">
          <t>Rearranged order of notification capability leafs into 3 groups:
          generic, specific to periodic subscriptions, specific to on-change.</t>
          <t>Introduced artwork folding in the examples</t>
          <t>Updated to follow draft-ietf-netmod-yang-instance-file-format-10</t>
          <t>Various editing changes</t>
        </list>
      </t>
      <t>v11 - v12
        <list style="symbols">
          <t>Updated max-nodes-per-update description</t>
          <t>Reformatted YANG models with pyang -f yang --keep-comments --yang-line-length 69</t>
        </list>
      </t>
      <t>v10 - v11
        <list style="symbols">
          <t>Updated examples</t>
          <t>Updated typedef notification-support</t>
        </list>
      </t>
      <t>v09 - v10
        <list style="symbols">
          <t>Removed description text from imports about the need for
          implementing the imported module.</t>
          <t>Changed notification-support to bits with shorter names</t>
          <t>Assigned enum values to supported-excluded-change-type</t>
          <t>Made node-selector a choice to allow for future alternative
          selection methods.</t>
          <t>Changed precedence of per-node-capabilities entries.
          Precedence is now according to the position of entries in
          the list.</t>
        </list>
      </t>
      <t>v08 - v09
        <list style="symbols">
          <t>Split the YANG module into two: ietf-system-capabilities
          and ietf-notification-capabilities. Restructured/updated the draft
          accordingly.</t>
        </list>
      </t>
      <t>v07 - v08
        <list style="symbols">
          <t>Prepared the YANG model to include other non-YANG-Push
          related capabilities.</t>
          <t>Renamed the top level container to system-capabilities</t>
          <t>Added a container subscription-capabilities to the grouping
          subscription-capabilities to contain all subscription
          related capabilities</t>
          <t>Updated examples according to
            draft-ietf-netmod-yang-instance-file-format-06.</t>
        </list>
      </t>
      <t>v06 - v07
        <list style="symbols">
          <t>Updated examples according to
            draft-ietf-netmod-yang-instance-file-format-05.</t>
        </list>
      </t>
      <t>v05 - v06
        <list style="symbols">
          <t>Providing the capability data is only a "SHOULD" recommendation.
          Some reviewers wanted MUST some wanted much less.</t>
          <t>The YANG module import statements now indicate the imported modules
          that must be implemented not just available as import as requested by
          the YangDoctors review.</t>
        </list>
      </t>
      <t>v04 - v05
        <list style="symbols">
          <t>Added new capabilities periodic-notifications-supported numbered="false" toc="default">
      <name>Acknowledgments</name>
      <t>For their valuable comments, discussions, and
            supported-excluded-change-type.</t>
          <t>Restructured YANG module to make the node-selector's usage similar
            to how NACM uses it: "/" means the whole datastore.</t>
          <t>Small corrections, spelling, rewording</t>
          <t>Replaced the term server with the term publisher except in cases
            where feedback, we speak about datastores and functionality based on
            get, getconfig operations. In this latter case it is really the
            server functionality that is discussed.</t>
        </list>
      </t>
      <t>v03 - v04
        <list style="symbols">
          <t>Clarified recommended support for on-change notifications about
            the datastore-subscription-capabilities.</t>
        </list>
      </t>
      <t>v02 - v03
        <list style="symbols">
          <t>Allow throughput related capabilities to be defined on top,
            datastore or data node level. Described that specific capability
            values always override generic ones.</t>
          <t>Indicate that non-NMDA servers can also use this model.</t>
          <t>Updated according wish to draft-ietf-netmod-yang-instance-file-format-04</t>
        </list>
      </t>
      <t>v01 - v02
        <list style="symbols">
          <t>Added instance data examples</t>
          <t>On-change capability can be defined per datastore</t>
          <t>Added "if-feature yp:on-change" where relevant</t>
          <t>Unified units used</t>
        </list>
      </t>
      <t>v00 - v01
        <list style="symbols">
          <t>Add more capabilities: minimum period, supported period
            max-number
        acknowledge <contact fullname="Andy Bierman"/>, <contact fullname="Juergen Schoenwaelder"/>, <contact fullname="Rob Wilton"/>, <contact fullname="Kent Watsen"/>,
        <contact fullname="Eric Voit"/>, <contact fullname="Joe Clarke"/>, <contact fullname="Martin Bjorklund"/>, <contact fullname="Ladislav Lhotka"/>, <contact fullname="Qin Wu"/>,
        <contact fullname="Mahesh Jethanandani"/>, <contact fullname="Ran Tao"/>, <contact fullname="Reshad Rahman"/>, and other members of objects, min dampening period,
            dampening supported</t>
        </list>
      </t> the Netmod Working Group.</t>
    </section>
  </back>
</rfc>
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