Subscription to Notifications in a Distributed Architecture
draft-ietf-netconf-distributed-notif-19

NETCONF                                                          T. Zhou
Internet-Draft                                                  G. Zheng
Intended status: Standards Track                                  Huawei
Expires: 16 October 2026                                         E. Voit
                                                           Cisco Systems
                                                                 T. Graf
                                                                Swisscom
                                                             P. Francois
                                                               INSA-Lyon
                                                           14 April 2026

      Subscription to Notifications in a Distributed Architecture
                draft-ietf-netconf-distributed-notif-19

Abstract

   This document describes extensions to the YANG notifications
   subscription to allow metrics being published directly from
   processors on line cards to target receivers, while subscription is
   still maintained at the route processor in a distributed forwarding
   system of a network node.

Requirements Language

   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.

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 16 October 2026.

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Copyright Notice

   Copyright (c) 2026 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 include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminologies . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Motivation and Solution Overview  . . . . . . . . . . . . . .   4
   4.  Solution Detail . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Subscription Decomposition  . . . . . . . . . . . . . . . . .   7
   6.  Publication Composition . . . . . . . . . . . . . . . . . . .   8
   7.  Subscription State Change Notifications . . . . . . . . . . .   8
   8.  Publisher Configurations  . . . . . . . . . . . . . . . . . .   8
   9.  YANG Tree . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   10. YANG Module . . . . . . . . . . . . . . . . . . . . . . . . .   9
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   12. Implementation Status . . . . . . . . . . . . . . . . . . . .  12
     12.1.  Huawei VRP . . . . . . . . . . . . . . . . . . . . . . .  12
     12.2.  6WIND VSR  . . . . . . . . . . . . . . . . . . . . . . .  13
   13. Operational Considerations  . . . . . . . . . . . . . . . . .  13
   14. Security Considerations . . . . . . . . . . . . . . . . . . .  13
   15. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  14
   16. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   17. References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     17.1.  Normative References . . . . . . . . . . . . . . . . . .  14
     17.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   The mechanism to support a subscription of a continuous and
   customized stream of updates from a YANG datastore [RFC8342] is
   defined in [RFC8639] and [RFC8641].  Requirements for Subscription to
   YANG Datastores are defined in [RFC7923].

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   By streaming YANG-Push notifications from publishers to receivers,
   much better performance and fine-grained sampling can be achieved
   than with a polling-based mechanism.  In a distributed forwarding
   system on a network node, the packet forwarding is delegated to
   multiple processors on line cards.  In order not to overwhelm the
   route processor resources, it is not uncommon that data records are
   published directly from processors on line cards to target receivers
   to further increase efficiency on the routing system.

   This document complements the general subscription requirements
   defined in Section 4.2.1 of [RFC7923] by adding the paragraph: A
   Subscription Service MAY support the ability to export from multiple
   software processes on a single routing system and expose the
   information which software process produced which message.

2.  Terminologies

   The following terms are defined in [RFC8639] and are not redefined
   here:

   Subscriber

   Publisher

   Receiver

   Subscription

   The following terms are used with "ietf-notification-capabilities" in
   Section 3 of [RFC9196] and are not redefined here:

   Notification Capabilities

   In addition, this document defines the below terms.  Some of these
   terms are distinguished between Network Node versus Component and
   Parent versus Agent to distinguish their role within the distributed
   system.  Network Node and Component is used to distinguish wherever
   the system component is reachable outside the distributed system or
   not.  Parent and Agent is used to distinguish wherever it manages or
   is being managed within the distributed system.

   Component: Refers to a network device component, such as a processor
   on a line card within a distributed routing system.

   Network Node Subscription: The Subscription requested by the
   Subscriber as described in Sections 2.4 and 2.5 of [RFC8639].  It may
   be decomposed into multiple Component Subscriptions.

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   Component Subscription: The Subscription that defines a data source
   which is managed and controlled by a single Publisher.

   Network Node Notification Capabilities: The overall notification
   capabilities that the group of Publishers can expose to the
   Subscriber as defined in Section 5.1 of [RFC9196] for the distributed
   system.  This includes which YANG nodes can be subscribed at which
   minimum-update-period for periodical subscriptions respectively which
   minimum-dampening-period for on-change subscriptions.

   Component Notification Capabilities: The notification capabilities
   that each Publisher exposes to the Publisher Parent.  This includes
   which YANG nodes with which minimum-update-period for periodical
   subscriptions respectively which minimum-dampening-period for on-
   change subscriptions can be subscribed on which Component.

   Publisher Parent: The component of a Publisher that interacts with
   the Subscriber to deal with the Network Node Subscription.  It
   decomposes the Network Node Subscription to multiple Component
   Subscriptions and interacts with the Publisher Agents.

   Publisher Agent: The component of a Publisher that interacts with the
   Publisher Parent to deal with the Component Subscription and pushing
   the data to the Receiver.

   Network Node: Is the network node of a distributed system which
   contains one or more Publishers that obtains the data from the YANG
   datastore and pushes it to the Receiver.

   Message Publisher: The Publisher that pushes the message to the
   Receiver.

   Message Publisher ID: A 32-bit identifier of the publishing process
   that is locally unique to the Network Node.  With this identifier the
   publishing process from where the message was published from can be
   uniquely identified.  Receivers SHOULD use the transport session and
   the Publisher ID field to separate different publisher streams
   originating from the same network Node.

3.  Motivation and Solution Overview

   In a distributed forwarding system of a Network Node much YANG data
   is subscribed to many Components, processors on line cards, but
   published from a single route processor instead.  This creates an
   unnecessary overhead at the route processor and a potential
   bottleneck.  Publishing the YANG data directly from the Components
   avoids this inefficiency.

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   This document proposes that subscribed YANG data can be published
   from Components for Section 2.5 of YANG-Push configured subscriptions
   [RFC8639].  The route processor is only involved in maintaining and
   decomposing the Subscription, which includes notifying the Receiver
   which Subscription is being published from which Component with
   subscription state change notifications.

   To enable Receivers to map notification messages to a particular
   Publisher, the Message Publisher ID in the transport message header
   of the YANG notification message is introduced.  In case of UDP
   transport, this is described in Section 3.2 of
   [I-D.ietf-netconf-udp-notif].  With unique sequence-numbers per
   publishing process described in Section 3.2.1 of
   [I-D.ietf-netconf-notif-envelope], each message can uniquely be
   identified, loss recognized and related to a transport session and
   publishing process.

4.  Solution Detail

   Figure 1 below shows the distributed data export framework.

   A collector usually includes two components,

   *  the Subscriber generates the subscription instructions to express
      what and how the Receiver wants to receive the data;

   *  the Receiver is the target for the data publication.

   For one subscription, there can be one or more Receivers.  And the
   Subscriber does not necessarily share the same IP address as the
   Receivers.

   In this framework, the Publisher pushes messages to the Receiver
   according to the subscription.  The Publisher is either in the Parent
   or Agent role.  The Publisher Parent knows all the capabilities that
   his Agents can provide and exposes the Network Node Notification
   Capabilities to the collector.  The Subscriber maintains the Network
   Node Subscription at the Publisher Parent and disassembles the
   Network Node Subscription to multiple Component Subscriptions,
   depending upon which source data is needed.  The Component
   Subscriptions are then distributed to the corresponding Publisher
   Agents on route and processors on line cards.

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   Publisher Agents collect metrics according to the Component
   Subscription, add its metadata, encapsulates, and pushes messages.
   Messages may require segmentation depending on the amount of YANG
   data subscribed and maximum transmission unit of the interface where
   the message is published from.  Implementations MUST NOT rely on IP
   fragmentation to carry large messages.  The Receiver then
   decapsulates packets and reassembles notifications accordingly.

                +-----------------------------------------+
                |        Collector        |-------------+ |
                |                        +------------+ | |
                |      +------------+    || Receiver  | | |
                |      | Subscriber |    |--------------+ |
                |      +-----^-+----+    +------^-----^   |
                |            | |                |     |   |
                +-----------------------------------------+
                 Network Node| |                |     |
                 Notification| | Network Node   |     |
                 Capabilities| | Subscription   |     |
                +-----------------------------------------+
                |            | |                |     |   |
                |            | |   Subscription |     |   |
                |            | |  State Changes |     |   |
                |            | |                |     |   |
                |   +--------+-v-------------------+  |   |
                |   |       Publisher(Parent)      |  |   |
                |   +--------^-+-------------------+  |   |
                |            | |                      |   |
                |            | |                      |   |
                |Component   | |                 Push |   |
                |Notification| | Component            |   |
                |Capabilities| | Subscription         |   |
                |   +--------+-v-------------------+  |   |
                |   |       Publisher(Agent)       +--+   |
                |   +------------------------------+      |
                |                                         |
                |            Network Node                 |
                +-----------------------------------------+

              Figure 1: The Distributed Data Export Framework

   Publisher Parent and Publisher Agents interact with each other in
   several ways:

   *  Publisher Agents need to register with the Parent at the beginning
      of their process life cycle.

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   *  Contracts are created and maintained throughout the subscription
      lifecycle between the Publisher Parent and each Agent and on its
      Component Notification Capabilities, and the format for
      notification data structure.

   *  The Publisher Parent relays the component subscriptions to the
      Publisher Agents.

   *  The Publisher Agents announce the status of their Component
      Subscriptions to the Publisher Parent.  The status of the overall
      subscription is maintained by the Publisher Parent.  The Publisher
      Parent is responsible for notifying the subscriber in case of
      problems with the Component Subscriptions.

   The technical mechanisms or protocols used for the coordination of
   operational information between Publisher Parent and Agent is out of
   scope of this document.

5.  Subscription Decomposition

   The Collector can send subscription requests only to the Parent.
   This requires the Publisher Parent to:

   1.  expose the Network Node Notification Capabilities that can be
       served by multiple Publisher Agents;

   2.  disassemble the Network Node Subscription to multiple Component
       Subscriptions, and distribute them to the Publisher Agents of the
       corresponding metric sources from the YANG schema tree so that
       they do not overlap; How the subscription is being distributed is
       implementation specific and not part of this document.

   3.  notify changes related to the existing subscriptions to the
       different Publisher Agents.

   And the Publisher Agent to:

   *  Inherit the Network Node Subscription properties from Publisher
      Parent for its Component Subscription;

   *  share the same life-cycle as the Network Node Subscription;

   *  share the same Subscription ID as the Network Node Subscription.

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6.  Publication Composition

   The Publisher Agent collects data and encapsulates the packets per
   Component Subscription.  The format and structure of the data records
   are defined by the YANG schema, so that the decomposition at the
   Receiver can benefit from the structured and hierarchical data
   records.

   The Receiver can associate the YANG data records with Subscription ID
   [RFC8639] to the subscribed subscription.  Additionally, it can use
   the Message Publisher ID to determine the corresponding publisher
   process.

   The "subscription-started" and "subscription-modified" notification
   defined in [RFC8639] and "push-update" and "push-change-update"
   notification defined in [RFC8641] MUST also include a list of Message
   Publisher IDs to notify the current Publishers for the corresponding
   Network Node Subscription.

7.  Subscription State Change Notifications

   In addition to sending event records to Receivers, the Parent MUST
   also send subscription state change notifications [RFC8639] when
   events related to subscription management have occurred.  All the
   subscription state change notifications MUST be delivered by the
   Parent.

   When the subscription decomposition result changes, the
   "subscription-modified" notification MUST be sent to indicate the new
   list of Publisher Agents.

8.  Publisher Configurations

   This document assumes that all Publisher Agents are preconfigured to
   push data.  Publisher Agents that send data are selected based on the
   subscription decomposition result.

   From the Receivers perspective, all Publisher Agents share the same
   source IP address for data export.  How connectivity is established
   within the distributed system architecture is out of scope of this
   document.  For connectionless data transport such as UDP based
   transport [I-D.ietf-netconf-udp-notif] the same Layer 4 source port
   for data export can be used.  For connection based data transport
   such as HTTPS based transport [I-D.ietf-netconf-https-notif], each
   Publisher Agent MUST be able to acknowledge packet retrieval from
   Receivers, and therefore requires a dedicated Layer 4 source port per
   software process.

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   The specific configuration on transports is described in the
   respective documents.

9.  YANG Tree

   module: ietf-distributed-notif

     augment /sn:subscriptions/sn:subscription:
       +--ro message-publisher-id*   uint32
     augment /sn:subscription-started:
       +--ro message-publisher-id*   uint32
     augment /sn:subscription-modified:
       +--ro message-publisher-id*   uint32
     augment /yp:push-update:
       +--ro message-publisher-id?   uint32
     augment /yp:push-change-update:
       +--ro message-publisher-id?   uint32

      Figure 2: YANG tree diagram for 'ietf-distributed-notif' module.

10.  YANG Module

   This YANG module imports definitions from [RFC8639] and [RFC8641].

   <CODE BEGINS> file "ietf-distributed-notif@2026-04-13.yang"
   module ietf-distributed-notif {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-distributed-notif";
     prefix dn;

     import ietf-subscribed-notifications {
       prefix sn;
       reference
         "RFC 8639: Subscription to YANG Notifications";
     }
     import ietf-yang-push {
       prefix yp;
       reference
         "RFC 8641: Subscription to YANG Notifications for Datastore
         Updates";
     }

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

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        Authors:  Guangying Zheng
                  <mailto:zhengguangying@huawei.com>
                  Tianran Zhou
                  <mailto:zhoutianran@huawei.com>
                  Thomas Graf
                  <mailto:thomas.graf@swisscom.com>
                  Pierre Francois
                  <mailto:pierre.francois@insa-lyon.fr>
                  Eric Voit
                  <mailto:evoit@cisco.com>";
     description
       "Defines augmentation for ietf-subscribed-notifications to
        enable the distributed publication with single subscription.

        Copyright (c) 2026 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 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).

        All revisions of IETF and IANA published modules can be found
        at the YANG Parameters registry
        (https://www.iana.org/assignments/yang-parameters).

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

     revision 2026-04-13 {
       description
         "Initial version";
       reference
         "RFC XXXX: Subscription to Notifications in a Distributed
          Architecture";
     }

     grouping message-publisher-id {
       description
         "Provides a reusable message-publisher-id leaf.";
       leaf message-publisher-id {
         type uint32;
         config false;
         description
           "Identifies the Component software process which publishes
            notification messages (e.g., processor 1 on line card 1). This

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            field is used to notify the receiver which publisher process
            published which message. The identifier is locally unique to
            the Network Node.";
       }
     }

     grouping message-publisher-ids {
       description
         "Provides a reusable message-publisher-id-list leaf-list.";
       leaf-list message-publisher-id {
         type uint32;
         config false;
         description
           "Identifies the Component software process which publishes
            notification messages (e.g., processor 1 on line card 1). This
            field is used to notify the receiver which publisher processes
            are going to publish. The identifiers are locally unique to
            the Network Node.";
       }
     }

     augment "/sn:subscriptions/sn:subscription" {
       description
         "This augmentation allows the Message
          Publisher ID to be exposed for a subscription.";
       uses message-publisher-ids;
     }

     augment "/sn:subscription-started" {
       description
         "This augmentation adds the Message Publisher ID to the
          subscription-started subscription change notifications.";
       uses message-publisher-ids;
     }

     augment "/sn:subscription-modified" {
       description
         "This augmentation adds the Message Publisher ID to the
          subscription-modified subscription change notifications.";
       uses message-publisher-ids;
     }

     augment "/yp:push-update" {
       description
         "This augmentation adds the Message Publisher ID in the
          push-update notification.";
       uses message-publisher-id;
     }

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     augment "/yp:push-change-update" {
       description
         "This augmentation adds the Message Publisher ID in the
          push-change-update notification.";
       uses message-publisher-id;
     }
   }
   <CODE ENDS>

11.  IANA Considerations

   This document registers the following namespace URI in the IETF XML
   Registry [RFC3688]:

      URI: urn:ietf:params:xml:ns:yang:ietf-distributed-notif

      Maintained by IANA?  N

      Registrant Contact: The IESG.

      XML: N/A; the requested URI is an XML namespace.

   This document registers the following YANG module in the YANG Module
   Names registry [RFC3688]:

      Name: ietf-distributed-notif

      Maintained by IANA?  N

      Namespace: urn:ietf:params:xml:ns:yang:ietf-distributed-notif

      Prefix: dn

      Reference: RFC XXXX

12.  Implementation Status

   Note to the RFC-Editor: Please remove this section before publishing.

12.1.  Huawei VRP

   Huawei implemented the Subscription Decomposition described in this
   document for a YANG-Push publisher on UDP-based Transport for
   Configured Subscriptions [I-D.ietf-netconf-udp-notif] in their VRP
   platform.

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12.2.  6WIND VSR

   6WIND implemented the Subscription Decomposition described in this
   document for a YANG-Push publisher on UDP-based Transport for
   Configured Subscriptions [I-D.ietf-netconf-udp-notif] in their VSR
   platform.

13.  Operational Considerations

   This document enables that subscriptions can be distributed among
   multiple Component subscriptions.  The ietf-distributed-notif YANG
   Module (Section 10) extends the Subscription state change, push-
   update and push-change-update notifications.  In Subscription state
   change notifications it describes from which YANG-Push Publisher IDs
   notifications are going to be published from.  In push-update and
   push-change-update notifications it describes from which YANG-Push
   Publisher ID the notification was published from.

   Both is important for operations to monitor at the YANG-Push Receiver
   wherever all Components are publishing notifications and thanks to
   unique sequence-numbers per publishing process Section 3.2.1 of
   [I-D.ietf-netconf-notif-envelope] and timestamp per message
   Section 3.3.1 of [I-D.ietf-netconf-notif-envelope] delay and loss per
   message and publishing process can be calculated.

14.  Security Considerations

   This section uses the template described in Section 3.7 of
   [I-D.ietf-netmod-rfc8407bis].

   The 'ietf-distributed-notif' YANG module defines a data model that is
   designed to be accessed via YANG-based management protocols, such as
   NETCONF [RFC6241] and RESTCONF [RFC8040].  These YANG-based
   management protocols (1) have to use a secure transport layer (e.g.,
   SSH [RFC6242], TLS [RFC8446], and QUIC [RFC9000]) and (2) have to use
   mutual authentication.

   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.

   There are no data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., "config true", which is the
   default).

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   Some of the readable data nodes in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get, get-config, or
   Notification) to these data nodes.  Specifically, the following
   subtrees and data nodes have particular sensitivities/
   vulnerabilities:

   *  /sn:subscriptions/sn:subscription/dn:message-publisher-id

   *  /sn:subscription-started/dn:message-publisher-id

   *  /sn:subscription-modified/dn:message-publisher-id

   *  /sn:establish-subscription/dn:message-publisher-id

   The entries in the list above will show the identity of the
   originating Publisher process.  Exposure of this information may
   assist an attacker in mapping the distributed system or in injecting
   spoofed Notifications.  Implementations SHOULD ensure that access to
   this data is restricted and that Notifications are sent over secure
   and authenticated channels.

   Security Considerations defined in [RFC8639] do also apply for this
   document.

15.  Contributors

      Alexander Clemm
      Futurewai
      2330 Central Expressway
      Santa Clara
      California
      United States of America
      Email: ludwig@clemm.org

16.  Acknowledgements

   We thank Kent Watsen, Mahesh Jethanandani, Martin Bjorklund, Tim
   Carey, Qin Wu, Robert Wilton, Benoit Claise, Alex Huang Feng, Camilo
   Cardona, Juergen Schoenwaelder, Joel Halpern and Yingzhen Qu for
   their constructive suggestions for improving this document.

17.  References

17.1.  Normative References

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

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

   [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>.

   [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>.

   [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>.

   [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>.

   [RFC8639]  Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard,
              E., and A. Tripathy, "Subscription to YANG Notifications",
              RFC 8639, DOI 10.17487/RFC8639, September 2019,
              <https://www.rfc-editor.org/info/rfc8639>.

   [RFC8641]  Clemm, A. and E. Voit, "Subscription to YANG Notifications
              for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
              September 2019, <https://www.rfc-editor.org/info/rfc8641>.

   [RFC9196]  Lengyel, B., Clemm, A., and B. Claise, "YANG Modules
              Describing Capabilities for Systems and Datastore Update
              Notifications", RFC 9196, DOI 10.17487/RFC9196, February
              2022, <https://www.rfc-editor.org/info/rfc9196>.

17.2.  Informative References

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   [I-D.ietf-netconf-https-notif]
              Jethanandani, M. and K. Watsen, "An HTTPS-based Transport
              for YANG Notifications", Work in Progress, Internet-Draft,
              draft-ietf-netconf-https-notif-15, 1 February 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-
              https-notif-15>.

   [I-D.ietf-netconf-notif-envelope]
              Feng, A. H., Francois, P., Graf, T., and B. Claise,
              "Extensible YANG Model for YANG-Push Notifications", Work
              in Progress, Internet-Draft, draft-ietf-netconf-notif-
              envelope-04, 6 February 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-
              notif-envelope-04>.

   [I-D.ietf-netconf-udp-notif]
              Feng, A. H., Francois, P., Zhou, T., Graf, T., and P.
              Lucente, "UDP-based Transport for Configured
              Subscriptions", Work in Progress, Internet-Draft, draft-
              ietf-netconf-udp-notif-25, 28 January 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-
              udp-notif-25>.

   [I-D.ietf-netmod-rfc8407bis]
              Bierman, A., Boucadair, M., and Q. Wu, "Guidelines for
              Authors and Reviewers of Documents Containing YANG Data
              Models", Work in Progress, Internet-Draft, draft-ietf-
              netmod-rfc8407bis-28, 5 June 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
              rfc8407bis-28>.

   [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>.

   [RFC7923]  Voit, E., Clemm, A., and A. Gonzalez Prieto, "Requirements
              for Subscription to YANG Datastores", RFC 7923,
              DOI 10.17487/RFC7923, June 2016,
              <https://www.rfc-editor.org/info/rfc7923>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [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>.

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   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,
              <https://www.rfc-editor.org/info/rfc9000>.

Appendix A.  Examples

   This appendix is non-normative.

   Figure 3 shows a typical configured subscription to the Network Node
   with distributed data export capability.  Subscripton request has
   been removed for brevity.

   +-------------+                 +-------------+ +-------------+
   | Receiver    |                 |  Publisher  | |  Publisher  |
   |             |                 |  (Parent)   | |  (Agent)    |
   +------+------+                 +------+------+ +------+------+
          |                               |               |
          | subscription-started, id#39   |               |
          | Message Publisher ID [#1,#2]  |               |
          +<------------------------------+               |
          |                               |               |
          | notif-mesg, id#39             |               |
          | Message Publisher ID #1       |               |
          +<------------------------------+               |
          |                               |               |
          | notif-mesg, id#39             |               |
          | Message Publisher ID #2       |               |
          +<----------------------------------------------+
          |                               |               |
          |                               |               |
          |                               |               |

              Figure 3: Call Flow for Configured Subscription

   Before starting to push data, the "subscription-started" subscription
   state notification is sent to the Receiver.  The following example
   assumes the NETCONF transport has already established.  The
   notification indicates that the configured subscription is decomposed
   into two component subscriptions which will be published by two
   message Message Publisher IDs: #1 and #2.

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 <notification xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0">
   <eventTime>2007-09-01T10:00:00Z</eventTime>
   <subscription-started
       xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
       xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
     <identifier>39</identifier>
     <yp:datastore
         xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
     ds:operational
     </yp:datastore>
     <yp:datastore-xpath-filter
         xmlns:ex="https://example.com/sample-data/1.0">
       /ex:foo
     </yp:datastore-xpath-filter>
     <yp:periodic>
         <yp:period>250</yp:period>
     </yp:periodic>
     <message-publisher-id
     xmlns="urn:ietf:params:xml:ns:yang:ietf-distributed-notif>
        1
     </message-publisher-id>
     <message-publisher-id
     xmlns="urn:ietf:params:xml:ns:yang:ietf-distributed-notif>
        2
     </message-publisher-id>
   </subscription-started>
 </notification>

    Figure 4: "subscription-started" Subscription State Notification

   Then, both Publishers send notifications with the corresponding data
   record to the Receiver.

Authors' Addresses

   Tianran Zhou
   Huawei
   156 Beiqing Rd., Haidian District
   Beijing
   China
   Email: zhoutianran@huawei.com

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   Guangying Zheng
   Huawei
   101 Yu-Hua-Tai Software Road
   Nanjing
   Jiangsu,
   China
   Email: zhengguangying@huawei.com

   Eric Voit
   Cisco Systems
   United States of America
   Email: evoit@cisco.com

   Thomas Graf
   Swisscom
   Binzring 17
   CH- Zuerich 8045
   Switzerland
   Email: thomas.graf@swisscom.com

   Pierre Francois
   INSA-Lyon
   Lyon
   France
   Email: pierre.francois@insa-lyon.fr

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