Yang-Push Notification Capabilities
draft-ietf-netconf-notification-capabilities-03

Document Type Active Internet-Draft (netconf WG)
Last updated 2019-08-13
Replaces draft-lengyel-netconf-notification-capabilities
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NETCONF                                                       B. Lengyel
Internet-Draft                                                  Ericsson
Intended status: Standards Track                                A. Clemm
Expires: February 14, 2020                                     Futurewei
                                                               B. Claise
                                                     Cisco Systems, Inc.
                                                         August 13, 2019

                  Yang-Push Notification Capabilities
            draft-ietf-netconf-notification-capabilities-03

Abstract

   This document proposes a YANG module that allows a server to specify
   server capabilities related to "Subscription to YANG Datastores"
   (Yang-Push).  It proposes to use YANG Instance Data to document this
   information and make it already available at implementation time, but
   also allow it to be reported at runtime.

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 February 14, 2020.

Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (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
   to this document.  Code Components extracted from this document must

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   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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Notification Capability Model . . . . . . . . . . . . . . . .   4
     3.1.  Tree Diagram  . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  YANG Module . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
     5.1.  The IETF XML Registry . . . . . . . . . . . . . . . . . .  12
     5.2.  The YANG Module Names Registry  . . . . . . . . . . . . .  12
   6.  Open Issues . . . . . . . . . . . . . . . . . . . . . . . . .  12
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  13
   Appendix A.  Instance data examples . . . . . . . . . . . . . . .  14
   Appendix B.  Changes between revisions  . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Terminology

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

   The terms Yang-Push, On-change subscription and Periodic subscription
   are used as defined in [I-D.ietf-netconf-yang-push]

   On-change Notification Capability: The capability of the server to
   support On-change subscriptions.

   The term Server is used as defined in [RFC8342]

   Implementation-time information: Information about the server's
   behavior that is made available during the implementation of the
   server, available from a source other then a running server.

   Runtime-information: Information about the server's behavior that is
   available from the running server via management protocols such as
   NETCONF [RFC6241] or RESTCONF [RFC8040].

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2.  Introduction

   As defined in [I-D.ietf-netconf-yang-push] a server may allow clients
   to subscribe to updates from a datastore and subsequently push such
   update notifications to the client.  Notifications may be sent
   periodically or on-change (more or less immediately after each
   change).

   A server supporting YANG-Push has a number of capabilities defined in
   [I-D.ietf-netconf-yang-push] that are often determined during the
   implementation of the server.  These include:

   o  Supported (reporting) periods for periodic subscriptions

   o  Maximum number of objects that can be sent in an update

   If the optional on-change feature is supported, additionally:

   o  Supported dampening periods for on-change subscriptions

   o  The set of data nodes for which on-change notification is
      supported

   Servers MAY have limitations in how many update notifications and how
   many datastore node updates they can send out in a certain time-
   period.

   In some cases, a publisher supporting on-change notifications will
   not be able to push updates for some object types on-change.  Reasons
   for this might be that the value of the datastore node changes
   frequently (e.g. in-octets counter), that small object changes are
   frequent and meaningless (e.g., a temperature gauge changing 0.1
   degrees), or that the implementation is not capable of on-change
   notification for a particular object.  In those cases, it will be
   important for client applications to have a way to identify for which
   objects on-change notifications are supported and for which ones not.

   Faced with the reality that support for on-change notification does
   not mean that such notifications will be sent for any specific data
   node, client/management applications can not rely on the on-change
   functionality unless the client has some means to identify for which
   objects on-change notifications are supported.  YANG models are meant
   to be used as an interface contract.  Without identification of the
   data nodes actually supporting on-change, this contract would be
   incomplete.

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   This document proposes a YANG module that allows a client to discover
   YANG-Push related capabilities both at implementation-time and run-
   time.

   Implementation time information is needed by Network Management
   System (NMS) implementers.  During NMS implementation for any
   functionality that depends on the notifications the information about
   on change notification capability is needed.  If the information is
   not available early in some document, but only as instance data from
   the network node once it is deployed, the NMS implementation will be
   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 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 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.

   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 operator needs to plan his
   management practices and NMS implementation before he even decides to
   buy the specific network node type.  Moreover the decision to buy the
   node type sometimes depends on these management possibilities.

   Run-time information is needed:

   o  for any "purely model driven" client, e.g. a NETCONF-browser.  As
      long as it has a valid model to read the capability information,
      it does not care which data nodes send notification, it will just
      handle what is available.

   o  in case the capability might change during run-time e.g. due to
      licensing, HW constraints etc.

   o  to check that early, implementation time capability information
      about the capabilities is indeed what the server implements (is
      the supplied documentation correct?)

3.  Notification Capability Model

   It is a goal to provide Yang-Push notification capability information
   in a format that is:

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   o  vendor independent

   o  formal

   o  identical for implementation-time and run-time

   The YANG module ietf-notification-capabilities is defined to provide
   the information.  It contains:

      a set of capabilities related to the amount of notifications the
      server can send out

      specification of which data nodes support on-change notifications.

      Capability values can be specified on server level, datastore
      level or on specific data nodes (and their contained sub-tree) of
      a specific datastore.  Capability values on a smaller, more
      specific part of the server's data always override more generic
      values.

      On-change capability is not specified on a server level as
      different datastores usually have different on-change
      capabilities.  On a datastore level on-change capability for
      configuration and state data can be specified separately.

   The information SHALL be provided in two ways both following the
   ietf-notification-capabilities module:

   o  For the implementation-time use-case: It SHALL be provided by the
      implementer as YANG instance data file complying to
      [I-D.ietf-netmod-yang-instance-file-format].  The file SHALL be
      available already in implementation time retrievable in a way that
      does not depend on a live network node.  E.g. download from
      product Website.

   o  For the run-time use-case: It SHALL be available via NETCONF
      [RFC6241] or RESTCONF [RFC8040] from the live server during
      runtime.  As these capabilities might change during run-time,
      implementations that support the YANG-Push on-change feature,
      SHOULD support sending on-change notifications about this module.

3.1.  Tree Diagram

   The following tree diagram [RFC8340] provides an overview of the data
   model.

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module: ietf-notification-capabilities
  +--ro datastore-subscription-capabilities
     +--ro (update-period)?
     |  +--:(minimum-update-period)
     |  |  +--ro minimum-update-period?     uint32
     |  +--:(supported-update-period)
     |     +--ro supported-update-period*   uint32
     +--ro max-objects-per-update?          uint32
     +--ro minimum-dampening-period?        uint32 {yp:on-change}?
     +--ro datastore-capabilities* [datastore]
        +--ro datastore                          union
        +--ro (update-period)?
        |  +--:(minimum-update-period)
        |  |  +--ro minimum-update-period?       uint32
        |  +--:(supported-update-period)
        |     +--ro supported-update-period*     uint32
        +--ro max-objects-per-update?            uint32
        +--ro minimum-dampening-period?          uint32 {yp:on-change}?
        +--ro on-change-supported-for-config?    boolean {yp:on-change}?
        +--ro on-change-supported-for-state?     boolean {yp:on-change}?
        +--ro per-node-capabilities* [node-selector]
           +--ro node-selector             nacm:node-instance-identifier
           +--ro (update-period)?
           |  +--:(minimum-update-period)
           |  |  +--ro minimum-update-period?    uint32
           |  +--:(supported-update-period)
           |     +--ro supported-update-period*  uint32
           +--ro max-objects-per-update?         uint32
           +--ro minimum-dampening-period?       uint32 {yp:on-change}?
           +--ro on-change-supported             boolean {yp:on-change}?

3.2.  YANG Module

   <CODE BEGINS> file "ietf-notification-capabilities@2019-08-13.yang"

module ietf-notification-capabilities {
  yang-version 1.1;
  namespace
    "urn:ietf:params:xml:ns:yang:ietf-notification-capabilities";
  prefix inc;

  import ietf-netconf-acm  { prefix nacm; }
  import ietf-yang-push    { prefix yp; }
  import ietf-yang-library {
    prefix yanglib;
    description
      "Requires revision 2019-01-04 or a revision derived from it.";
  }

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  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 related server
     capabilities.

     The module contains
     - capabilities related to the amount of notifications the
     server can send out. (Note that for a specific subscription
     the server MAY still allow only longer periods or smaller
     updates depending on e.g. actual load conditions.)
     - specification of which data nodes support on-change
     notifications.

     Capability values on a
     smaller, more specific part of the server's data always override
     more generic values. The hierarchy of specifications from generic
     to more specific is:
      1) top level values valid for all datastores
      2) values for a specific datastore (including the special
        'all' datastore identifier)
      3) Value for a specific data node and its contained sub-tree
        in one of the datastores. Such capability values are inherited
        down the containment tree unless a more specific value is
        provided, as described in 4)
      4) A contained, smaller, more specific sub-tree in a specific
        datastore (could be a single leaf)

      Any capability value MAY be absent if a more generic capability
      value is already provided or if the server is not capable of
      providing a value.

     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) 2019 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

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     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 BSD License
     set forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (http://trustee.ietf.org/license-info).

     This version of this YANG module is part of RFC XXXX; see
     the RFC itself for full legal notices.";

  revision 2019-08-13 {
    description
      "Initial version";
    reference
      "RFC XXX: Yang-Push Notification Capabilities";
  }

  container datastore-subscription-capabilities {
    config false;
    description
      "YANG-Push related server capabilities";

    grouping datastore-subscription-throughput-capabilities {
      description "Capability values that affect the amount of
        notifications the server can send out.";

      choice update-period {
        description
          "Supported update-period values.";
        leaf minimum-update-period {
          type uint32;
          units "centiseconds";
          description
            "Minimum update period supported for a
            periodic subscription.";
        }

        leaf-list supported-update-period {
          type uint32;
          units "centiseconds";
          description
            "Specific supported update period values
            for a periodic subscription.";
        }
      }

      leaf max-objects-per-update {
        type uint32 {

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              range "1..max";
        }
        description
          "Maximum number of objects that can be sent
           in an update.";
      }

      leaf minimum-dampening-period {
        if-feature yp:on-change ;
        type uint32;
        units "centiseconds";
        description
          "The minimum dampening period supported for on-change
           subscriptions.";
      }
    }

    uses datastore-subscription-throughput-capabilities {
      description "Top level throughput capabilities.
        These values can be overridden by values provided per
        datastore or for individual data nodes in a datastore.";
    }

    list datastore-capabilities {
      key datastore ;
      description "Capabilities values per datastore.
        For non-NMDA servers the config=false data is considered
        as if it was part of the running datastore.

        Indicates per datastore throughput capabilities.

        Indicates per datastore the data nodes for which the
        server is capable of sending on-change notifications.
        If a datastore implemented by the server is not specified
        in this list and there is no list element for 'all' datastores
        the datastore does not support any on-change notifications.

        On-change notifications SHALL be sent for a config=true
        data node if one of the following is true:
        - if it is a top level data-node and is not specified in the
        per-node-capabilities list and on-change-supported-for-config
        is true; or
        - notifications are sent for its parent data node and it is
        not specified in the per-node-capabilities list; or
        - it is specified in the per-node-capabilities list and has
        an on-change-supported value true.

        On-change notifications SHALL be sent for a config=false

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        data node if one of the following is true:
        - if it is a top level data-node (a config=false data node with
        a config=true parent SHALL be treated as a top level data node)
        and is not specified in the per-node-capabilities list and
        on-change-supported-for-state is true; or
        - notifications are sent for its parent data node
        which is also config=false and it is not specified in the
        per-node-capabilities list; or
        - it is specified in the per-node-capabilities list and has
        an on-change-supported value true";

      leaf datastore {
        type union {
          type leafref {
            path /yanglib:yang-library/yanglib:datastore/yanglib:name ;
          }
          type enumeration {
            enum all ;
          }
        }
        must '. != "all" or count(..) = "1" ' {
          error-message
            "If 'all' is present individual datastores cannot be " +
              "specified.";
        }
        description "The datastore for which capabilities are defined.";
      }

      uses datastore-subscription-throughput-capabilities {
        description "Throughput capabilities for a datastore.
          These values will override top level values and can be
          overridden by values provided for individual data nodes
          in a datastore.";
      }

      leaf on-change-supported-for-config {
        if-feature yp:on-change ;
        type boolean;
        default "true";
        description
          "Specifies the default value for
           top level config=true data nodes for the
           on-change-supported capability.";
      }

      leaf on-change-supported-for-state {
        if-feature yp:on-change ;
        type boolean;

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        default "false";
        description
          "Specifies the default value for
           top level config=false data nodes for the
           on-change-supported capability.";
      }

      list per-node-capabilities {
        key "node-selector";
        description
          "A list of data nodes that have either a throughput or
           on-change-notification capability specifically defined.

           Should be used only when specific data nodes support
           capabilities that are different from capabilities
           of their parent nodes or the default for the datastore.";

        leaf node-selector {
          type nacm:node-instance-identifier;
          description
            "Selects the data nodes for which
             a capability is specified.";
        }

        uses datastore-subscription-throughput-capabilities {
          description "Throughput capabilities for a specific data node.
            These values will override top level or datastore
            specific values.";
        }

        leaf on-change-supported {
          if-feature yp:on-change ;
          type boolean;
          mandatory true;
          description
            "Specifies whether the server is capable of
             sending on-change notifications for the selected
             data nodes.";
        }
      }
    }
  }
}

   <CODE ENDS>

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4.  Security Considerations

   The YANG module specified in this document defines a schema for data
   that is designed to be accessed via network management protocols such
   as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer
   is the secure transport layer, and the mandatory-to-implement secure
   transport is Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer
   is HTTPS, and the mandatory-to-implement secure transport is TLS
   [RFC8446].

   The Network Configuration Access Control Model (NACM) [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.

   The data in this module is not security sensitive.

5.  IANA Considerations

5.1.  The IETF XML Registry

   This document registers one URI in the IETF XML registry [RFC3688].
   Following the format in [RFC3688], the following registrations are
   requested:

      URI: urn:ietf:params:xml:ns:yang:ietf-notification-capabilities
      Registrant Contact: The NETCONF WG of the IETF.
      XML: N/A, the requested URI is an XML namespace.

5.2.  The YANG Module Names Registry

   This document registers one YANG module in the YANG Module Names
   registry [RFC7950].  Following the format in [RFC7950], the the
   following registrations are requested:

  name:       ietf-notification-capabilities
  namespace:  urn:ietf:params:xml:ns:yang:ietf-notification-capabilities
  prefix:     inc
  reference:  RFC XXXX

6.  Open Issues

      -

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7.  References

7.1.  Normative References

   [I-D.ietf-netconf-yang-push]
              Clemm, A. and E. Voit, "Subscription to YANG Datastores",
              draft-ietf-netconf-yang-push-25 (work in progress), May
              2019.

   [I-D.ietf-netmod-yang-instance-file-format]
              Lengyel, B. and B. Claise, "YANG Instance Data File
              Format", draft-ietf-netmod-yang-instance-file-format-04
              (work in progress), August 2019.

   [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>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

7.2.  Informative 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>.

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   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

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

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

Appendix A.  Instance data examples

   The following example is instance-data describing the notification
   capabilities of a hypothetical "acme-switch".  The switch implements
   the running, candidate and operational datastores.  Every change can
   be reported on-change from running, nothing from candidate and all
   config=false data from operational.

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 <?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>
   <module>ietf-notification-capabilities@2019-08-13.yang</module>
   <!-- revision date, contact, etc. -->
   <description>Notification capabilities of acme-switch.
     Acme-switch implements the running, candidate and operational
     datastores. Every change can be reported on-change from running,
     nothing from candidate and all config=false data from operational.
       </description>
   <content-data>
     <datastore-subscription-capabilities>
       <minimum-update-period>500</minimum-update-period>
       <max-objects-per-update>2000</max-objects-per-update>
       <minimum-dampening-period>100</minimum-dampening-period>
       <datastore-capabilities>
         <datastore xmlns="urn:ietf:params:xml:ns:yang:ietf-datastores">
           running
         </datastore>
         <!-- Neither on-change-supported-for-config nor
         on-change-supported-for-state are present as the
         default values are in effect. -->
       </datastore-capabilities>
       <!-- The candidate datastore is implemented, but not present
       here as it does not support any on-change notifications. -->
       <datastore-capabilities>
         <datastore xmlns="urn:ietf:params:xml:ns:yang:ietf-datastores">
           operational
         </datastore>
         <on-change-supported-for-config>
           false
         </on-change-supported-for-config>
         <on-change-supported-for-state>
           true
         </on-change-supported-for-state>
       </datastore-capabilities>
     </datastore-subscription-capabilities>
   </content-data>
 </instance-data-set>

         Figure 1: Notification Capabilities with default settings

   The following is the instance-data describing the notification
   capabilities of a hypothetical "acme-router".  The router implements
   the running, and operational datastores.  Every change can be
   reported on-change from running, but only config=true nodes and some

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   config=false data from operational.  Interface statistics are not
   reported on-change only 2 important counters.

<?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>
  <module>ietf-notification-capabilities@2019-08-13.yang</module>
  <!-- revision date, contact, etc. -->
  <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 running, but
    only config=true nodes and some config=false data from operational.
    Statistics are not reported on-change only 2 important counters,
    for these a smaller dampening period is possible.
      </description>
  <content-data>
    <datastore-subscription-capabilities
     xmlns="urn:ietf:params:xml:ns:yang:ietf-notification-capabilities">
      <minimum-update-period>500</minimum-update-period>
      <max-objects-per-update>2000</max-objects-per-update>
      <minimum-dampening-period>100</minimum-dampening-period>
      <datastore-capabilities>
        <datastore xmlns="urn:ietf:params:xml:ns:yang:ietf-datastores">
          running
        </datastore>
      </datastore-capabilities>
      <datastore-capabilities>
        <datastore xmlns="urn:ietf:params:xml:ns:yang:ietf-datastores">
          operational
        </datastore>
        <on-change-supported-for-state>
          true
        </on-change-supported-for-state>
        <per-node-capabilities>
          <node-selector>
            /if:interfaces/if:interface/if:statistics</node-selector>
          <on-change-supported>false</on-change-supported>
        </per-node-capabilities>
        <per-node-capabilities>
          <node-selector>
            /if:interfaces/if:interface/if:statistics/if:in-octets
          </node-selector>
          <minimum-dampening-period>10</minimum-dampening-period>
          <on-change-supported>true</on-change-supported>
        </per-node-capabilities>
        <per-node-capabilities>
          <node-selector>

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            /if:interfaces/if:interface/if:statistics/if:out-octets
          </node-selector>
          <on-change-supported>true</on-change-supported>
          <minimum-dampening-period>10</minimum-dampening-period>
        </per-node-capabilities>
      </datastore-capabilities>
    </datastore-subscription-capabilities>
  </content-data>
</instance-data-set>

   Figure 2: Notification Capabilities with data node specific settings

Appendix B.  Changes between revisions

   v02 - v03

   o  Allow throughput related capabilities to be defined on top,
      datastore or data node level.  Described that specific capability
      values always override generic ones.

   o  Indicate that non-NMDA servers can also use this model.

   o  Updated according to draft-ietf-netmod-yang-instance-file-
      format-04

   v01 - v02

   o  Added instance data examples

   o  On-change capability can be defined per datastore

   o  Added "if-feature yp:on-change" where relevant

   o  Unified units used

   v00 - v01

   o  Add more capabilities: minimum period, supported period max-number
      of objects, min dampening period, dampening supported

Authors' Addresses

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   Balazs Lengyel
   Ericsson
   Magyar Tudosok korutja 11
   1117 Budapest
   Hungary

   Email: balazs.lengyel@ericsson.com

   Alexander Clemm
   Futurewei
   2330 Central Expressway
   Santa Clara, CA 95050
   USA

   Email: ludwig@clemm.org

   Benoit Claise
   Cisco Systems, Inc.
   De Kleetlaan 6a b1
   1831 Diegem
   Belgium

   Email: bclaise@cisco.com

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