Augmented-by Addition to the YANG Library
draft-ietf-netconf-yang-library-augmentedby-08

NETCONF                                                           Z. Lin
Internet-Draft                                                 B. Claise
Intended status: Standards Track                                  Huawei
Expires: 4 January 2026                         I. D. Martinez-Casanueva
                                                              Telefonica
                                                             3 July 2025

               Augmented-by Addition to the YANG Library
             draft-ietf-netconf-yang-library-augmentedby-08

Abstract

   This document augments the ietf-yang-library to provide the
   augmented-by list.  It facilitates the process of obtaining all
   dependencies between YANG modules, by querying the network management
   server's YANG library.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Source for this draft and an issue tracker can be found at
   https://github.com/Zephyre777/draft-lincla-netconf-yang-library-
   augmentation.

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
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   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 4 January 2026.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Data Mesh Architecture  . . . . . . . . . . . . . . . . .   6
     3.2.  Data Catalog  . . . . . . . . . . . . . . . . . . . . . .   7
   4.  The "ietf-yang-library-augmentedby" YANG module . . . . . . .   9
     4.1.  Data Model Overview . . . . . . . . . . . . . . . . . . .   9
       4.1.1.  Tree View . . . . . . . . . . . . . . . . . . . . . .   9
       4.1.2.  YANG Module . . . . . . . . . . . . . . . . . . . . .   9
     4.2.  Implementation Instructions . . . . . . . . . . . . . . .  12
       4.2.1.  The scope of augmented-by . . . . . . . . . . . . . .  12
       4.2.2.  An example of YANG module augmented-by result . . . .  13
   5.  Implementation Status . . . . . . . . . . . . . . . . . . . .  14
     5.1.  Netopeer2 at IETF119 Hackathon  . . . . . . . . . . . . .  14
     5.2.  Netopeer2 at IETF120 Hackathon  . . . . . . . . . . . . .  15
     5.3.  Libyangpush Find-dependency . . . . . . . . . . . . . . .  15
     5.4.  Device Implementations  . . . . . . . . . . . . . . . . .  15
   6.  Changes . . . . . . . . . . . . . . . . . . . . . . . . . . .  15
     6.1.  draft-lincla-netconf-yang-library-augmentation: Changes
            from 00 to 01  . . . . . . . . . . . . . . . . . . . . .  15
     6.2.  draft-lincla-netconf-yang-library-augmentedby version
            00 . . . . . . . . . . . . . . . . . . . . . . . . . . .  16
     6.3.  draft-lincla-netconf-yang-library-augmentedby: Changes from
            00 to 01 . . . . . . . . . . . . . . . . . . . . . . . .  16
     6.4.  draft-lincla-netconf-yang-library-augmentedby: Changes from
            01 to 02 . . . . . . . . . . . . . . . . . . . . . . . .  16
     6.5.  draft-ietf-netconf-yang-library-augmentedby version 00  .  16
     6.6.  draft-ietf-netconf-yang-library-augmentedby: Changes from
            00 to 01 . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.7.  draft-ietf-netconf-yang-library-augmentedby: Changes from
            01 to 02 . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.8.  draft-ietf-netconf-yang-library-augmentedby: Changes from
            02 to 03 . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.9.  draft-ietf-netconf-yang-library-augmentedby: Changes from
            03 to 04 . . . . . . . . . . . . . . . . . . . . . . . .  17

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     6.10. draft-ietf-netconf-yang-library-augmentedby: Changes from
            04 to 05 . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.11. draft-ietf-netconf-yang-library-augmentedby: Changes from
            05 to 06 . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.12. draft-ietf-netconf-yang-library-augmentedby: Changes from
            06 to 07 . . . . . . . . . . . . . . . . . . . . . . . .  18
     6.13. draft-ietf-netconf-yang-library-augmentedby: Changes from
            07 to 08 . . . . . . . . . . . . . . . . . . . . . . . .  18
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  18
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  19
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  19
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  20
   Appendix A.  Full Tree View of ietf-yang-library  . . . . . . . .  22
   Appendix B.  YANG module validation with yanglint . . . . . . . .  23
     B.1.  An ietf-yang-library yang-library data XML example  . . .  24
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  25
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  25
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  25

1.  Introduction

   The YANG library [RFC8525] provides information about the data model
   supported by the server.  This is presented as an inventory of YANG
   modules.  It helps a client with listing all datastores supported by
   a network management server and the schema that is used by each of
   these datastores.

   According to Section 4.2.8 and 5.6.3 in [RFC7950], augment defines
   additional nodes to the module while deviations change (add, modify,
   delete) properties (sub-statements) to other module's schema nodes.
   They provide crucial information about the YANG data model
   composition, and is referred to as reverse dependency in this
   document: this means the behavior of a schema node depends on
   external modifications, creating flow backward from the augmenting/
   deviation module to the base module.

   Currently it is difficult to obtain the YANG schema tree (defined in
   Section 3 in [RFC7950]) without obtaining and parsing all the YANG
   modules from a management server.  The deviation list defined in YANG
   library enables client to obtain the module reverse dependency
   without having to get and parse all YANG modules.  However, the
   augmentation list is not defined in it.

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   Since both augmentation and deviation work as YANG module
   dependencies, it is reasonable to document them the same way in the
   YANG library.  Having both augmentation and deviation directly
   available in the YANG library provides an easy and light-weight
   solution for determining the reverse dependencies.

   Therefore, this document proposes a YANG module that augments the
   YANG library to include the YANG module augmentation information.

1.1.  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 terminology from [RFC8525] is used in this document

   The term "client" is used as defined in [RFC6241] for NETCONF and
   [RFC8040] for RESTCONF.

   The term "YANG schema tree" is used as defined in the terminology in
   [RFC7950]

   The term 'NMDA' which is defined as the title of [RFC8342] is used in
   this document.

   Tree diagrams in this document use the notation defined in [RFC8340]
   .

   This document defines the folloing term:

   *  Reverse Dependency: The dependency YANG modules that provide
      modification to the behavior of a base YANG module's schema node,
      creating flow backward from the augmenting/deviation module to the
      base module, while they are not specified in the base module as
      opposed to the 'import' or 'include'.

2.  Motivation

   When using YANG modules, it is necessary to make sure that all its
   dependencies are presented.  [RFC7950] identifies four types of
   dependencies between YANG modules:

   *  Import: the "import" statement allows a module or submodule to
      reference definitions defined in other modules.

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   *  Include: the "include" statement is used in a module to identify
      each submodule that belongs to it.

   *  Augment: the augmentation defines the location in the data model
      hierarchy where additional nodes are inserted.

   *  Deviation: the "deviation" statement defines a fragment of a
      module that the server does not implement.

   The import and include are direct dependencies which can be obtained
   by parsing the YANG module source code, while the augmentation and
   deviation are reverse dependencies which are defined in another
   module.

   For the reverse dependencies, since they are defined externally, it
   is not possible to discover them by parsing the YANG module.  The
   current way to discover the reverse dependencies is to query all YANG
   modules from the server and parse them.  This is a lengthy process,
   which must be repeated for each client that requires this
   information.

   According to the definition of the module ietf-yang-library defined
   in [RFC8525], the "deviation" list describes that a module is
   deviated by which other modules.  If the YANG library could directly
   report all reverse dependencies, it would provide a much easier and
   light-weight solution to find module all dependencies, compared to
   obtaining and parsing all modules.

   The YANG library only provides the deviation list, without
   augmentations.  With augmentations being more widely used and
   defined, and with use cases to automate network management,
   augmentations become essential information for clients to better
   understand the network management server module relationships.  Thus,
   the YANG library should be extended to also provide the augmentation
   information.

   From the perspective of the operational efficiency, it is easy to
   adapt the device implementation to include augmentation, since
   augmentation and deviation work similarly.

3.  Use Cases

   As the demand for YANG-based telemetry [RFC8641] arises, there is a
   need for real-time knowledge of a specific YANG module's dependency
   list when a specific YANG-Push notification for a given subscription
   is received.

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   The alternative for a YANG-Push receiver is to collect and store the
   entire module set for every single server who could be streaming
   data.  This approach is not always practical due to the following
   reasons:

   *  A YANG-push receiver will not know which YANG-Push publisher sent
      the subscribed YANG content until the first notification is
      received.

   *  For a YANG-Push receiver => from which YANG-Push publisher the
      subscribed YANG content is going to be received is not known until
      the first notification is being received.

   *  Querying all the YANG modules is time-consuming and add overhead
      considering that only a subset of the YANG nodes of the management
      server are subscribed to.

   This section introduces two use cases that reflect the motivation for
   extending the YANG library.  One targets solving dependency problems
   in a data mesh architecture while the other aims at building a data
   catalog that makes YANG module information easily accessible.

3.1.  Data Mesh Architecture

   A network analytics architecture that integrates YANG-Push and Kafka
   is introduced in draft: An Architecture for YANG-Push to Apache Kafka
   Integration [I-D.ietf-nmop-yang-message-broker-integration].  This
   open-source project encompasses contributions such as Support of
   Versioning in YANG Notifications Subscription
   [I-D.ietf-netconf-yang-notifications-versioning] or Support of
   Network Observation Timestamping in YANG Notifications
   [I-D.netana-netconf-notif-envelope], among others.

   The purpose of this project is to provide adequate information to the
   YANG-Push notifications so that the module and its dependencies can
   be parsed and retrieved automatically from the vantage point.  The
   architecture relies on the information of YANG dependencies to
   realize, to solve the problem of missing YANG semantics when
   notifications are transformed or indexed in Time Series Database.  As
   a solution to provide the missing YANG semantics, a schema registry
   is introduced to store YANG modules and all their relationships
   (Direct and reverse dependencies).  The schema is obtained by NETCONF
   <get-schema> operation (defined in Section 3.1 of [RFC6022]) of the
   subscribed YANG schema tree, which is obtained by parsing the
   <subscription-started> message of each YANG-Push subscription.

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   When obtaining the dependency modules of a YANG module, an
   independent process containing multiple <get-schema> operations
   [RFC6022] is launched after each new YANG-Push subscription module
   has been known.  However, the complexity remains at:

   *  How dependencies of YANG modules are found (so that the YANG-Push
      subscription message has the complete set of module dependencies
      for its subscribed YANG schema tree)?

   *  How do we conduct <get-schema>?

   Currently, the method used for obtaining modules and finding module
   dependencies is getting the full set of supported YANG modules from
   the network device.  This process is very heavy because in practice,
   each device may implement hundreds of YANG modules, requiring up to
   several minutes to complete the YANG modules retrieval.  Besides, the
   need for parsing all YANG modules and finding all the dependencies
   adds an extra delay.  Obtaining all dependencies through this method
   makes the operation very costly, since after each subscribed module
   is learned, the operation of getting the full set of modules needs to
   be performed again.

   Therefore, considering the Network Observability real-time aspects,
   this extra delay in collecting (and processing) the dependencies
   through the approach of getting the full set of modules is not
   realistic.

   It's more efficient to get dependencies only for the required
   modules.

   By using the provided the augmentation information in ietf-yang-
   library, the YANG-Push receiver can directly obtain the YANG reverse
   dependencies by obtaining the contents of the YANG library, saving
   collection (and processing time) at the YANG-Push receiver and
   therefore helping with the real-time aspects of Network Observability
   and enabling closed-loop actions.

3.2.  Data Catalog

   Finding the YANG modules implemented by a network management server
   is paramount for configuring and monitoring the status of a network.
   However, since the inception of YANG the network industry has
   experienced a tsunami of YANG modules developed by SDOs, open-source
   communities, and network vendors.  This heterogeneity of YANG
   modules, that vary from one network device model to another, makes
   the management of a multi-vendor network a big challenge for
   operators.  [Martinez-Casanueva2023]

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   In this regard, a data catalog provides a registry of the datasets
   exposed by remote data sources for consumers to discover data of
   interest.  Besides the location of the dataset (i.e., the data
   source), the data catalog registers additional metadata such as the
   data model (or schema) followed in the dataset or even related terms
   defined in a business glossary.

   Data catalog solutions typically implement collectors that ingest
   metadata from the data sources themselves and external metadata
   sources.  For example, a Kafka Schema Registry is a metadata source
   that provides metadata about the data models followed by some data
   stored in a Kafka topic.

   In this sense, a YANG-enabled network device can be considered as
   another kind of data source, which the Data Catalog can pull metadata
   from.  For instance, the data catalog can include a connector that
   fetches metadata about the YANG modules implemented by the network
   device.  Combining these metadata with other such as the business
   concept "interface", would enable data consumers to discover which
   datasets related to the concept "interface" are exposed by the
   network device.

   Network devices that implement YANG library expose metadata about
   which YANG modules are implemented, and which are only imported.
   However, what a data consumer needs at the end are the YANG modules
   implemented by the device, hence, the combination of implemented YANG
   modules with other YANG modules that might deviate or augment the
   formers.

   Coming back to the example of datasets related to the "interface"
   concept, say we have a network device that implements the ietf-
   interfaces module [RFC8343] and the ietf-ip module [RFC8344], where
   the latter augments the former.  For a data catalog to collect these
   metadata, a connector would retrieve YANG library data from the
   target device.  However, the current version of YANG library would
   not satisfy the use case as it would tell that the device implements
   both ietf-interfaces and ietf-ip modules, but will miss the augment
   dependency between them.

   The current workaround is in combination with the YANG library data
   to additionally obtain both YANG modules and process them to discover
   that there is an augment dependency.  This adds extra burden on the
   connector, which is forced to combine multiple metadata collection
   mechanisms.  This process could be softened by extending YANG library
   to also capture augment dependencies, in a similar fashion to
   deviation dependencies.

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4.  The "ietf-yang-library-augmentedby" YANG module

   This YANG module augments the ietf-yang-library module by adding the
   augmented-by leaf-list in the "yang-library/module-set" and "yang-
   library/modules-state".  The name of list "augmented-by" indicates by
   which modules that the current module is being directly augmented.

   The "yang-library/module-state" is augmented despite its "deprecated"
   state to cope with the situation when container "modules-state" is
   used for compatibility reason with ietf-yang-library defined in
   [RFC7895].  Both the NMDA[RFC8342] and non-NMDA compliant additions
   are defined in the same YANG module for simplicity for users and
   implementors.

   For the scope of "augmented-by", this draft only considers the direct
   augmentation relationship.  The recursive result of augmentation or
   transitive dependency for module specified along the XPath, is out of
   the scope of this draft.  Section 4.2 has given the implementation
   instructions.

4.1.  Data Model Overview

4.1.1.  Tree View

   The following is the YANG tree diagram for model ietf-yang-library-
   augmentedby.

   module: ietf-yang-library-augmentedby

     augment /yanglib:yang-library/yanglib:module-set/yanglib:module:
       +--ro augmented-by*   -> ../../yanglib:module/name
     augment /yanglib:modules-state/yanglib:module:
       +--ro augmented-by*   -> ../../yanglib:module/name

4.1.2.  YANG Module

   The YANG module source code of ietf-yang-library-augmentedby in which
   augmentation to the ietf-yang-library of [RFC8525] is defined.

   <CODE BEGINS> file "ietf-yang-library-augmentedby@2025-05-28.yang"
   module ietf-yang-library-augmentedby {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-yang-library-augmentedby";
     prefix yanglib-aug;

     import ietf-yang-library {
       prefix yanglib;
       reference

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         "RFC 8525: YANG Library";
     }

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

        Author:   Zhuoyao Lin
                  <mailto:zhuoyao.lin1@huawei-partners.com>
                  Benoit Claise
                  <mailto:benoit.claise@huawei.com>
                  Ignacio Dominguez Martinez-Casanueva
                  <matilto:ignacio.dominguezmartinez@telefonica.com>";

     description
       "This module augments the ietf-yang-library defined in
        [RFC8525] to provide not only the deviation list, but also
        the augmented-by list, in order to give sufficient
        information about the YANG modules reverse dependency. It
        facilitates the process of obtaining the entire
        dependencies of YANG module.

        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) 2025 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).
        This version of this YANG module is part of RFC XXXX; see the
        RFC itself for full legal notices.  ";

     revision 2025-05-28 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: Augmented-by Addition to the YANG Library";

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     }

     grouping augmented-by {
       description
         "Augment the augmented-by leaf-list from module info with the
         module-augmented-by grouping" ;

       leaf-list augmented-by {
         type leafref {
           path "../../yanglib:module/yanglib:name";
         }

         description
           "Leaf-list of the augmentation used by this server to
            modify the conformance of the module associated with
            this entry.  Note that the same module can be used for
            augmented-by for multiple modules, so the same
            entry MAY appear within multiple 'module' entries.

            This reference MUST NOT (directly or indirectly)
            refer to the module being augmented.

            Robust clients may want to make sure that they handle a
            situation where a module augments itself (directly or
            indirectly) gracefully.";
       }
     }

     augment "/yanglib:yang-library/yanglib:module-set/yanglib:module" {
       description
         "Augments the augmented-by leaf-list from module info with the
          augmented-by grouping.

          The 'augmented-by' leaf-list should only consider those YANG
          modules that directly augment the YANG module associated
          with this entry, and the augmenting and augmented modules
          should be defined in the same module-set.

          The 'directly augment' is identified by the relationship
          between the augment module and the target node's parent
          module that it augments to. Only the direct parent module
          of the target node is augmented, and the rest of the parent
          modules defined in the schema tree are only indirect
          dependencies but not augmented modules. (Refer to
          'Target node' definition in Section 7.17 of RFC7950)
          " ;
         uses augmented-by;
     }

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     augment "/yanglib:modules-state/yanglib:module" {
       status deprecated;
       description
         "Augments the augmented-by leaf-list from module info with the
          augmented-by grouping.

          The 'augmented-by' leaf-list should only consider those YANG
          modules that directly augment the YANG module associated
          with this entry, and the augmenting and augmented modules
          should be defined in the same module-set.

          The 'directly augment' is identified by the relationship
          between the augment module and the target node's parent
          module that it augments to. Only the direct parent module
          of the target node is augmented, and the rest of the parent
          modules defined in the schema tree are only indirect
          dependencies but not augmented modules. (Refer to
          'Target node' definition in Section 7.17 of RFC7950)
          " ;
         uses augmented-by;
     }

   }
   <CODE ENDS>

4.2.  Implementation Instructions

4.2.1.  The scope of augmented-by

   This section explains the scope of augmented-by.

   The "augmented-by" leaf-list should only consider those YANG modules
   that directly augment the YANG module in question in the ietf-yang-
   library, and the augmenting and augmented modules should be defined
   in the same module-set.

   The "direct augment" is identified by the relationship between the
   augment module and the target node's parent module that it augments
   to.  Only the direct parent module of the target node is augmented,
   and the rest of the parent modules defined in the schema tree are
   only indirect dependencies but not augmented modules.  (Refer to
   "Target node" definition in Section 7.17 of [RFC7950])

   In the case when a YANG application requires recursive dependency or
   specific schema tree dependency, the search logic should be
   implemented by the application itself.

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   A YANG example with the expected augmented-by result is provided in
   Section 4.2.2.

4.2.2.  An example of YANG module augmented-by result

   This section provides a module-set to explain the definition of
   "direct augment" stated in Section 4.2.1.

   There are Modules A, B, C, which have the following relationships:

   *  Module A is the base module with container "foo-a"

   *  Module B augments "/a:foo-a" with container "foo-b"

   *  Module C augments "/a:foo-a/b:foo-b" with leaf "leaf-c"

   In this example, while the XPath that Module C augments to contains
   container "foo-a" defined in Module A, the actual target node it
   directly augments to is "foo-b" in Module B.  Therefore, Module C is
   not an augmentation for Module A and does not appear in the
   "augmented-by" leaf-list of Module A.  Only Module B, which is
   directly augmenting to "foo-a", is an "augmented-by" for Module A.

   The augmented-by XML result for Modules A, B and C is the following:

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   <CODE BEGINS>
   file "example_augmentedby_result.xml"
   <yang-library xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library">
     <content-id>1</content-id>
     <module-set>
       <name>module-set1</name>
       <module>
         <name>a-module</name>
         <revision>2025-06-18</revision>
         <namespace>urn:ietf:params:xml:ns:yang:a-module</namespace>
         <augmented-by
         xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library-augmentedby">b-module</augmented-by>
       </module>
       <module>
         <name>b-module</name>
         <revision>2025-06-18</revision>
         <namespace>urn:ietf:params:xml:ns:yang:b-module</namespace>
         <augmented-by
         xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library-augmentedby">c-module</augmented-by>
       </module>
       <module>
         <name>c-module</name>
         <revision>2025-06-18</revision>
         <namespace>urn:ietf:params:xml:ns:yang:c-module</namespace>
       </module>
     </module-set>
   </yang-library>
   <modules-state xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library">
     <module-set-id>0</module-set-id>
   </modules-state>
   <CODE ENDS>

5.  Implementation Status

   Note to the RFC-Editor: Please remove this section before publishing
   (This follows the template in RFC7942).

5.1.  Netopeer2 at IETF119 Hackathon

   Zhuoyao Lin did the prototype implementation of the augmented-by list
   feature of this draft and demonstrated it based on Netopeer2 in IETF
   119 Hackathon.

   Netopeer2 is a NETCONF server & client implementation developed by
   CESNET.  Source code is here: [NTP17].  The actual feature is
   implemented by extending the libyang [LY16] and sysrepo [SR16] which
   are the base libraries for Netopeer2 to support populating the
   augmented-by list.

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5.2.  Netopeer2 at IETF120 Hackathon

   Zhuoyao Lin did a docker image of netopeer2 that integrates the
   augmented-by feauture in sysrepo and libyang.  The result is
   presented at IETF 120 hackathon.

   The source code can be obtained here: [NP24]

5.3.  Libyangpush Find-dependency

   Zhuoyao Lin did an implementation of find-dependency based on the
   ietf-yang-library with augmented-by feature in the YANG-Push message
   parser library libyangpush.  The result is presented in IETF 120
   hackathon.

   The source code can be obtained here: [NP24]

5.4.  Device Implementations

   This section introduced the device implementations status [NA25] of
   this document from vendors like Huawei, Cisco, 6Wind.

   The list of Router Images supporting (upcoming and already
   implemented) the ietf-yang-library-augmentedby YANG module proposed
   in this document is following:

   *  Huawei VRP R025C00 for NE8000 and NE40 (2025-10-15).
      https://support.huawei.com/

   *  Cisco IOS XR 25.3.1 (2025-08-31). https://software.cisco.com/

   *  Huawei VRP R024C10 for MA5800T-X17 (2025-06-30).
      https://support.huawei.com/

   *  6WIND VSR 3.10. https://www.6wind.com/

6.  Changes

6.1.  draft-lincla-netconf-yang-library-augmentation: Changes from 00 to
      01

   The list name has been updated from "augmentation" to "augmented-by",
   in order to represent the usage clearly.

   The leafref has been changed from absolute path "/yanglib:yang-
   libraray/yanglib:module-set/yanglib:module/yanglib:name" to relative
   path "../../yanglib:module/yanglib:name".  The YANG validation in the
   appendix B shows that this path can work as expected.

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   Section 5 Implementation and section 6 Changes has been added.

6.2.  draft-lincla-netconf-yang-library-augmentedby version 00

   Updated the Use case content in Section 3.1.  Add explanation: the
   scope of use case "Data Mesh Architecture" is limited to configured
   subscription.

   Updated Implementation status content.

6.3.  draft-lincla-netconf-yang-library-augmentedby: Changes from 00 to
      01

   Updated affiliations

   Update content of Section 3.1 Data Mesh use case.  Explain the
   limitation of applying get-all-schemas solution under the background
   of using UDP-notif of configured subscription, and how the feature
   proposed in the draft can improve the solution.

   Full review of document.  Nits and refinement of sections.

6.4.  draft-lincla-netconf-yang-library-augmentedby: Changes from 01 to
      02

   Rewrite Section 2 Motivation.

   Update Section 6 Changes's subsection title.

   Update the Section 7 security consideration and section 8 IANA
   Considerations.

   Added in the appendix the Impact Analysis of ietf-yang-library and
   proposal for the RFC8525bis draft.

6.5.  draft-ietf-netconf-yang-library-augmentedby version 00

   Resubmitted the draft name from:

   draft-lincla-netconf-yang-library-augmentedby-02

   to:

   draft-ietf-netconf-yang-library-augmentedby-00

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6.6.  draft-ietf-netconf-yang-library-augmentedby: Changes from 00 to 01

   Correct the yanglint validation invalid example.

   Updated the explaination to the yanglint validation example
   principle.

   Delete Section "ietf-yang-library Impact Analysis, as an evaluation
   for RFC8525bis".  The idea of updating the RFC8525 is paused.

6.7.  draft-ietf-netconf-yang-library-augmentedby: Changes from 01 to 02

   Update and rephrase the Introduction section.

   Add Section 4.2 Implementation Instructions.  Address in
   Section 4.2.1 that the definition of "augmented-by" only consider the
   direct augment.  A YANG example for explaining this purpose has been
   put into Section 4.2.2.

   Draft refinement.

   Reference update.

6.8.  draft-ietf-netconf-yang-library-augmentedby: Changes from 02 to 03

   Merge review comment from Thomas.

6.9.  draft-ietf-netconf-yang-library-augmentedby: Changes from 03 to 04

   Update module content ietf-yang-library-augmentedby: Organise the
   augmentation content to grouping; Add augmentation to modules-state
   container.

   Appendix B is deleted.

6.10.  draft-ietf-netconf-yang-library-augmentedby: Changes from 04 to
       05

   Update ietf-yang-library-augmentedby module revision.

6.11.  draft-ietf-netconf-yang-library-augmentedby: Changes from 05 to
       06

   Merged Jean, Thomas and Alex's editorial feedback.

   Merged Andy's review.

   Changed contents are listed following:

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   *  Section 1: Rewrite introduction.  Added definition for 'reverse
      dependency'.  Avoid possible misleading expression about reverse
      dependency and external dependency.

   *  Section 2: Editorial Changes.

   *  Section 3: Merged editorial feedback from Alex, mainly for
      Section 3.1.

   *  Section 4: Move the full tree diagram to appendix A; Correct the
      YANG file date; Update the description statement in YANG module to
      provide implementation instructions information; Improve the text
      of implementation instruction and the direct augment example.

   *  Appendix: For Appendix A: The ietf-yang-library full tree view has
      been moved to Appendix A.  For Appendix B: The yanglint validation
      example has been moved from Appendix A to Appendix B.  The invalid
      yanglint example has been removed.  Set up texted has been added
      before the validation example.

6.12.  draft-ietf-netconf-yang-library-augmentedby: Changes from 06 to
       07

   Change the reference in IANA Consideration to 'RFC-to-be'.

6.13.  draft-ietf-netconf-yang-library-augmentedby: Changes from 07 to
       08

   Merged Per's review and comments.

7.  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.

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   The readable node defined 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 this data node.  The following is the explanation of
   data node's sensitivity/vulnerability:

   The "augmented-by" list in this YANG module could reveal all modules
   that are augmenting one module.  It could help attacker identify the
   relationship between modules and server implementations known bugs.
   Server vulnerabilities may include but not restricted to: 1.  Too
   many augmented-by records cause buffer overflow. 2.  The augmented-by
   list helps identify through the inter-relation of modules how to
   cause the server to crash or significantly degrade device
   performance.

8.  IANA Considerations

   This document registers one URI in the "IETF XML Registry" [RFC3688].
   Following the format in [RFC3688], the following registration has
   been made.

   URI: urn:ietf:params:xml:ns:yang:ietf-yang-library-augmentedby

   Registration Contact: The NETCONF WG of the IETF.

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

   This document registers one YANG module in the "YANG Module Names"
   registry [RFC6020]

   name: ietf-yang-library-augmentedby

   namespace: urn:ietf:params:xml:ns:yang:ietf-yang-library-augmentedby

   prefix: yanglib-aug

   reference: RFC-to-be

9.  References

9.1.  Normative References

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

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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>.

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

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

   [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>.

   [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>.

   [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>.

   [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>.

   [RFC8343]  Bjorklund, M., "A YANG Data Model for Interface
              Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
              <https://www.rfc-editor.org/info/rfc8343>.

   [RFC8344]  Bjorklund, M., "A YANG Data Model for IP Management",
              RFC 8344, DOI 10.17487/RFC8344, March 2018,
              <https://www.rfc-editor.org/info/rfc8344>.

   [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>.

9.2.  Informative References

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   [I-D.ietf-netconf-yang-notifications-versioning]
              Graf, T., Claise, B., and A. H. Feng, "Support of
              Versioning in YANG Notifications Subscription", Work in
              Progress, Internet-Draft, draft-ietf-netconf-yang-
              notifications-versioning-08, 5 April 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netconf-
              yang-notifications-versioning-08>.

   [I-D.ietf-nmop-yang-message-broker-integration]
              Graf, T., "An Architecture for YANG-Push to Apache Kafka
              Integration", Work in Progress, Internet-Draft, draft-
              ietf-nmop-yang-message-broker-integration, 3 July 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-nmop-
              yang-kafka-integration>.

   [I-D.netana-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-netana-netconf-notif-
              envelope, <https://datatracker.ietf.org/doc/html/draft-
              netana-netconf-notif-envelope>.

   [LY16]     Vasko, M., "libyang", BSD-3-Clause license, November 2016,
              <https://github.com/CESNET/libyang.git>.

   [Martinez-Casanueva2023]
              Martinez-Casanueva, I. D., Gonzalez-Sanchez, D., Bellido,
              L., Fernandez, D., and D. R. Lopez, "Toward Building a
              Semantic Network Inventory for Model-Driven Telemetry",
              DOI 10.1109/MCOM.001.2200222, March 2023,
              <https://doi.org/10.1109/MCOM.001.2200222>.  IEEE
              Communications Magazine

   [NA25]     "IETF YANG-Push - Implementations", <https://www.network-
              analytics.org/yp/implementations.html>.

   [NP24]     Lin, Z., "Netopeer2-docker-ietf120", July 2024,
              <https://github.com/network-
              analytics/libyangpush/tree/feature/draft_augmentedby>.

   [NTP17]    Vasko, M., "Netopeer2", BSD-3-Clause license, May 2017,
              <https://github.com/CESNET/netopeer2>.

   [RFC6022]  Scott, M. and M. Bjorklund, "YANG Module for NETCONF
              Monitoring", RFC 6022, DOI 10.17487/RFC6022, October 2010,
              <https://www.rfc-editor.org/info/rfc6022>.

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   [RFC7895]  Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module
              Library", RFC 7895, DOI 10.17487/RFC7895, June 2016,
              <https://www.rfc-editor.org/info/rfc7895>.

   [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>.

   [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>.

   [RFC8525]  Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
              and R. Wilton, "YANG Library", RFC 8525,
              DOI 10.17487/RFC8525, March 2019,
              <https://www.rfc-editor.org/info/rfc8525>.

   [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>.

   [SR16]     Vasko, M., "sysrepo", BSD-3-Clause license, January 2016,
              <https://github.com/sysrepo/sysrepo.git>.

Appendix A.  Full Tree View of ietf-yang-library

   The following is the YANG tree diagram [RFC8340] for module ietf-
   yang-library after adding augmentation from module ietf-yang-library-
   augmentedby.  The RPCs and notifications are included as well.

  module: ietf-yang-library
    +--ro yang-library
    |  +--ro module-set* [name]
    |  |  +--ro name                  string
    |  |  +--ro module* [name]
    |  |  |  +--ro name                        yang:yang-identifier
    |  |  |  +--ro revision?                   revision-identifier
    |  |  |  +--ro namespace                   inet:uri
    |  |  |  +--ro location*                   inet:uri
    |  |  |  +--ro submodule* [name]
    |  |  |  |  +--ro name        yang:yang-identifier
    |  |  |  |  +--ro revision?   revision-identifier
    |  |  |  |  +--ro location*   inet:uri
    |  |  |  +--ro feature*                    yang:yang-identifier
    |  |  |  +--ro deviation*                  -> ../../module/name
    |  |  |  +--ro yanglib-aug:augmented-by*
                                       -> ../../yanglib:module/name

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    |  |  +--ro import-only-module* [name revision]
    |  |     +--ro name         yang:yang-identifier
    |  |     +--ro revision     union
    |  |     +--ro namespace    inet:uri
    |  |     +--ro location*    inet:uri
    |  |     +--ro submodule* [name]
    |  |        +--ro name        yang:yang-identifier
    |  |        +--ro revision?   revision-identifier
    |  |        +--ro location*   inet:uri
    |  +--ro schema* [name]
    |  |  +--ro name          string
    |  |  +--ro module-set*   -> ../../module-set/name
    |  +--ro datastore* [name]
    |  |  +--ro name      ds:datastore-ref
    |  |  +--ro schema    -> ../../schema/name
    |  +--ro content-id    string
    x--ro modules-state
       x--ro module-set-id    string
       x--ro module* [name revision]
          x--ro name                yang:yang-identifier
          x--ro revision            union
          +--ro schema?             inet:uri
          x--ro namespace           inet:uri
          x--ro feature*            yang:yang-identifier
          x--ro deviation* [name revision]
          |  x--ro name        yang:yang-identifier
          |  x--ro revision    union
          x--ro conformance-type    enumeration
          x--ro submodule* [name revision]
          |  x--ro name        yang:yang-identifier
          |  x--ro revision    union
          |  +--ro schema?     inet:uri
          +--ro yanglib-aug:augmented-by*   -> ../../yanglib:module/name

    notifications:
      +---n yang-library-update
      |  +--ro content-id    -> /yang-library/content-id
      x---n yang-library-change
         x--ro module-set-id    -> /modules-state/module-set-id

Appendix B.  YANG module validation with yanglint

   This section gives an example of the yang-library content that the
   user can try themselves with yanglint.  This is created to
   demonstrate and validate the correct syntax.  The example should be
   compiled with YANG modules ietf-yang-library and ietf-yang-library-
   augmentedby as schemas.

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   The examples provided are ietf-yang-library 'yang-library' data XML
   file containing the augmented-by field.

B.1.  An ietf-yang-library yang-library data XML example

   The yang-library XML example concerns the following module-set:

   There are module1, module2, module3, which have the following
   relationships:

   *  Module 1 is the base module with container "foo1"

   *  Module 2 augments "/module1:foo1" with container "foo2"

   *  Module 3 augments "/module1:foo1" with leaf "leaf3"

   All three YANG modules are defined in the same module-set name 'ms1'
   to be able to augment or be augmented by the others.  Otherwise, the
   yanglint validation should fail.

   The example is following:

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   <CODE BEGINS> file "example_valid.xml"
   <yang-library xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library">
     <content-id>1</content-id>
     <module-set>
       <name>ms1</name>
       <module>
         <name>module1</name>
         <revision>2024-02-29</revision>
         <namespace>urn:ietf:params:xml:ns:yang:module1</namespace>
         <augmented-by
         xmlns="urn:ietf:params:xml:ns:yang:
         ietf-yang-library-augmentedby">module2</augmented-by>
         <augmented-by
         xmlns="urn:ietf:params:xml:ns:yang:
         ietf-yang-library-augmentedby">module3</augmented-by>
       </module>
       <module>
         <name>module2</name>
         <revision>2024-02-29</revision>
         <namespace>urn:ietf:params:xml:ns:yang:module2</namespace>
       </module>
       <module>
         <name>module3</name>
         <revision>2024-02-29</revision>
         <namespace>urn:ietf:params:xml:ns:yang:module3</namespace>
       </module>
     </module-set>
   </yang-library>
   <modules-state xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library">
       <module-set-id>0</module-set-id>
   </modules-state>
   <CODE ENDS>

Contributors

   The following people all contributed to creating this document:

Acknowledgments

   The author would like to thank Jan Lindblad and Jean Quilbeuf for
   their help during the design of the YANG module, and Thomas Graf, Rob
   Wilton, Andy Bierman, Jean Quilbeuf, Alex Huang Feng, Per Andersson
   for their valuable review and comments.

Authors' Addresses

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   Zhuoyao Lin
   Huawei
   Townsend Street, 4th Floor George's Court
   Dublin
   Ireland
   Email: zhuoyao.lin1@huawei-partners.com

   Benoit Claise
   Huawei
   Email: benoit.claise@huawei.com

   Ignacio Dominguez Martinez-Casanueva
   Telefonica
   Ronda de la Comunicacion, S/N
   Madrid 28050
   Spain
   Email: ignacio.dominguezmartinez@telefonica.com

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