NETMOD Working Group                                               Q. Wu
Internet-Draft                                                 B. Claise
Updates: 8407 (if approved)                                       Huawei
Intended status: Standards Track                                  P. Liu
Expires: 24 December 2022                                          Z. Du
                                                            China Mobile
                                                            M. Boucadair
                                                                  Orange
                                                            22 June 2022


                       Node Tags in YANG Modules
                     draft-ietf-netmod-node-tags-08

Abstract

   This document defines a method to tag nodes that are associated with
   operation and management data in YANG modules.  This method for
   tagging YANG nodes is meant to be used for classifying either data
   nodes or instances of data nodes from different YANG modules and
   identifying their characteristic data.  Tags may be registered as
   well as assigned during the definition of the module, assigned by
   implementations, or dynamically defined and set by users.

   This document also provides guidance to future YANG data model
   writers; as such, this document updates RFC 8407.

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 24 December 2022.

Copyright Notice

   Copyright (c) 2022 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
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Sample Use Cases for Node Tags  . . . . . . . . . . . . . . .   5
   4.  Node Tag Values . . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  IETF Tags . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  Vendor Tags . . . . . . . . . . . . . . . . . . . . . . .   6
     4.3.  User Tags . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.4.  Reserved Tags . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Node Tag Management . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  Module Design Tagging . . . . . . . . . . . . . . . . . .   7
     5.2.  Implementation Tagging  . . . . . . . . . . . . . . . . .   7
     5.3.  User Tagging  . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Node Tags Module Structure  . . . . . . . . . . . . . . . . .   7
     6.1.  Node Tags Module Tree . . . . . . . . . . . . . . . . . .   7
   7.  Node Tags YANG Module . . . . . . . . . . . . . . . . . . . .   8
   8.  Guidelines to Model Writers . . . . . . . . . . . . . . . . .  12
     8.1.  Define Standard Tags  . . . . . . . . . . . . . . . . . .  12
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  YANG Data Node Tag Prefixes Registry  . . . . . . . . . .  13
     9.2.  IETF YANG Data Node Tags Registry . . . . . . . . . . . .  14
     9.3.  Updates to the IETF XML Registry  . . . . . . . . . . . .  15
     9.4.  Updates to the YANG Module Names Registry . . . . . . . .  15
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  16
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  16
   12. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  17
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  17
     13.2.  Informative References . . . . . . . . . . . . . . . . .  18
   Appendix A.  Example: Additional Auxiliary Data Property
           Information . . . . . . . . . . . . . . . . . . . . . . .  19
   Appendix B.  Instance Level Tunnel Tagging Example  . . . . . . .  20
   Appendix C.  NETCONF Example  . . . . . . . . . . . . . . . . . .  22
   Appendix D.  Non-NMDA State Module  . . . . . . . . . . . . . . .  23
   Appendix E.  Targeted Data Fetching Example . . . . . . . . . . .  27
   Appendix F.  Changes between Revisions  . . . . . . . . . . . . .  29
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  31




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1.  Introduction

   The use of tags for classification and organization purposes is
   fairly ubiquitous, not only within IETF protocols, but globally in
   the Internet (e.g., "#hashtags").  For the specific case of YANG data
   models, a module tag is defined as a string that is associated with a
   module name at the module level [RFC8819].

   Many data models have been specified by various Standards Developing
   Organizations (SDOs) and the Open Source community, and it is likely
   that many more will be specified.  These models cover many of the
   networking protocols and techniques.  However, data nodes defined by
   these technology-specific data models might represent only a portion
   of fault, configuration, accounting, performance, and security
   (FCAPS) management information ([FCAPS]) at different levels and
   network locations, but also categorized in various different ways.
   Furthermore, there is no consistent classification criteria or
   representations for a specific service, feature, or data source.

   This document defines tags for both nodes in the schema tree and
   instance nodes in the data tree and shows how they can be associated
   with nodes within a YANG module, which:

   *  Provide dictionary meaning for specific targeted data nodes;

   *  Indicate a relationship between data nodes within the same YANG
      module or from different YANG modules;

   *  Identify auxiliary data properties related to data nodes;

   *  Identify key performance metric related data nodes and the
      absolute XPath expression identifying the element path to the
      nodes.

   To that aim, this document defines a YANG module [RFC7950] that
   augments the YANG Module Tags ([RFC8819]) to provide a list of node
   entries to add or remove node tags as well as to view the set of node
   tags associated with specific data nodes or instance of data nodes
   within YANG modules.  This new module is: "ietf-node-tags"
   (Section 7).

   Typically, NETCONF clients can discover node tags supported by a
   NETCONF server by means of the <get-data> operation on the
   operational datastore (Section 3.1 of [RFC8526]) via the "ietf-node-
   tags" module.  Alternatively, <get-schema> operation can be used to
   retrieve tags for nodes in the schema tree in any data module.  These
   node tags can be used by a NETCONF [RFC6241] or RESTCONF [RFC8040]
   client to classify either data nodes or instance of these data nodes



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   from different YANG modules and identify characteristic data and
   associated path to the nodes or node instances.  Therefore, the
   NETCONF/ RESTCONF client can query specific configuration or
   operational state on a server corresponding to characteristic data.

   Similar to YANG module tags defined in [RFC8819], these node tags
   (e.g., tags for node in the schema node) may be registered or
   assigned during the module definition, assigned (e.g., tags for nodes
   in the data tree) by implementations, or dynamically defined and set
   by users.  The contents of node tags from the operational state view
   are constructed using the following steps:

   1.  System tags (i.e., tags of "system" origin) that assigned during
       the module definition time are added;

   2.  User-configured tags (i.e., tags of "intended" origin) that
       dynamically defined and set by users at runtime;

   3.  Any tag that is equal to a masked-tag is removed.

   This document defines an extension statement to indicate tags for
   data nodes.  YANG metadata annotations are also defined in [RFC7952]
   as a YANG extension.  The value of YANG metadata annotations is
   attached to a given data node instance and decided and assigned by
   the server and sent to the client (e.g., the origin value indicates
   to the client the origin of a particular data node instance) while
   tags for data node in the schema tree defined in Section 7 are
   retrieved centrally via the "ietf-node-tags" module and can be
   dynamically set by the client.

   This document also defines an IANA registry for tag prefixes and a
   set of globally assigned tags (Section 9).

   Section 8 provides guidelines for authors of YANG data models.  This
   document updates [RFC8407].

   The YANG data model in this document conforms to the Network
   Management Datastore Architecture defined in [RFC8342].

2.  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.





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   The following terms are defined in [RFC7950] and are not redefined
   here:

   *  Data Node

   *  Data Tree

   *  Schema Tree

   This document defines the following term:

   Node Tag:  Tag for YANG nodes used for classifying either data nodes
      or instances of data nodes from different YANG modules and
      identifying their characteristic data.

   The meanings of the symbols in tree diagrams are defined in
   [RFC8340].

3.  Sample Use Cases for Node Tags

   The following lists a set of use cases to illustrate the use of node
   tags.  This section does not intend to be exhaustive.

   An example of the use of tags is to search discrete categories of
   YANG nodes that are scattered across the same or different YANG
   modules supported by a device.  For example, if instances of these
   nodes in YANG modules are adequately tagged and set by a first client
   ("client A") via the "ietf-node-tags" module (Section 7) and
   retrieved by another client ("client B") from the operational
   datastore, then "client B" can obtain the path to the tagged nodes
   and subscribe only to network performance related data node instances
   in the operational datastore supported by a device.

   "Client B" can also subscribe to updates from the operational
   datastore using the "ietf-node-tags" module.  Any tag changes in the
   updates will then resynchronize to the "client B".

   Also, tag classification is useful for users searching data nodes
   repositories.  A query restricted to the "ietf:counter" data node tag
   in the "ietf-node-tags" module can be used to return only the YANG
   nodes that are associated with the counter.  Without tags, a user
   would need to know the name of all the IETF YANG data nodes or
   instances of data nodes in different YANG modules.

   Future management protocol extensions could allow for filtering
   queries of configuration or operational state on a server based on
   tags (for example, return all operational state related to system
   management).



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4.  Node Tag Values

   All node tags (except in some cases of user tags as described in
   Section 4.3) begin with a prefix indicating who owns their
   definition.  An IANA registry (Section 9.1) is used to register node
   tag prefixes.  Initially, three prefixes are defined.

   No further structure is imposed by this document on the value
   following the registered prefix, and the value can contain any YANG
   type 'string' characters except carriage returns, newlines, tabs, and
   spaces.

   Except for the conflict-avoiding prefix, this document is
   purposefully not specifying any structure on (i.e., restricting) the
   tag values.  The intent is to avoid arbitrarily restricting the
   values that designers, implementers, and users can use.  As a result
   of this choice, designers, implementers, and users are free to add or
   not add any structure they may require to their own tag values.

4.1.  IETF Tags

   An IETF tag is a node tag that has the prefix "ietf:".

   All IETF node tags are registered with IANA in the registry defined
   in Section 9.2.

4.2.  Vendor Tags

   A vendor tag is a tag that has the prefix "vendor:".

   These tags are defined by the vendor that implements the module, and
   are not registered with IANA.  However, it is RECOMMENDED that the
   vendor includes extra identification in the tag to avoid collisions,
   such as using the enterprise or organization name following the
   "vendor:" prefix (e.g., vendor:entno:vendor-defined-classifier).

4.3.  User Tags

   User tags are defined by a user/administrator and are not registered
   by IANA.

   Any tag with the prefix "user:" is a user tag.  Furthermore, any tag
   that does not contain a colon (":", i.e., has no prefix) is also a
   user tag.  Users are not required to use the "user:" prefix; however,
   doing so is RECOMMENDED.






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4.4.  Reserved Tags

   Section 9.1 describes the IANA registry of tag prefixes.  Any prefix
   not included in that registry is reserved for future use, but tags
   starting with such a prefix are still valid tags.

5.  Node Tag Management

   Tags may be associated with a data node within a YANG module in a
   number of ways.  Typically, tags may be defined and associated at the
   module design time, at implementation time without the need of a live
   server, or via user administrative control.  As the main consumers of
   node tags are users, users may also remove any tag from a live
   server, no matter how the tag became associated with a data node
   within a YANG module.

5.1.  Module Design Tagging

   A data node definition MAY indicate a set of node tags to be added by
   a module's implementer.  These design time tags are indicated using
   'node-tag' extension statement.

   If the data node is defined in an IETF Standards Track document, node
   tags MUST be IETF Tags (Section 4.1).  Thus, new data nodes can drive
   the addition of new IETF tags to the IANA registry defined in
   Section 9.2, and the IANA registry can serve as a check against
   duplication.

5.2.  Implementation Tagging

   An implementation MAY include additional tags associated with data
   nodes within a YANG module.  These tags SHOULD be IETF ((i.e.,
   registered) ) or vendor tags.

5.3.  User Tagging

   Node tags of any kind, with or without a prefix, can be assigned and
   removed by the user from a server using normal configuration
   mechanisms.  In order to remove a node tag from the operational
   datastore, the user adds a matching "masked-tag" entry for a given
   node within the 'ietf-node-tags' module.

6.  Node Tags Module Structure

6.1.  Node Tags Module Tree

   The tree associated with the "ietf-node-tags" module is as follows:




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   module: ietf-node-tags
   augment /tags:module-tags/tags:module:
     +--rw node-tags
        +--rw node* [id]
           +--rw id           nacm:node-instance-identifier
           +--rw tags* [tag]
           |  +--rw tag       tags:tag
           |  +--rw type?     identityref
           +--rw masked-tag*  tags:tag

                Figure 1: YANG Module Node Tags Tree Diagram

7.  Node Tags YANG Module

   The "ietf-node-tags" module imports types from [RFC8819] and
   [RFC8341].

   <CODE BEGINS> file "ietf-node-tags@2022-02-04.yang"
   module ietf-node-tags {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-node-tags";
     prefix ntags;

     import ietf-netconf-acm {
       prefix nacm;
       reference
       "RFC 8341: Network Configuration Access Control
                  Model";
     }
     import ietf-module-tags {
       prefix tags;
       reference
       "RFC 8819: YANG Module Tags ";
     }

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

       Editor: Qin Wu
               <mailto:bill.wu@huawei.com>

       Editor: Benoit Claise
               <mailto:benoit.claise@huawei.com>

       Editor: Peng Liu



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               <mailto:liupengyjy@chinamobile.com>

       Editor: Zongpeng Du
               <mailto:duzongpeng@chinamobile.com>

       Editor: Mohamed Boucadair
               <mailto:mohamed.boucadair@orange.com>";
      // RFC Ed.: replace XXXX with actual RFC number and
      // remove this note.
     description
       "This module describes a mechanism associating
        tags with YANG node within YANG modules. Tags may be IANA
        assigned or privately defined.

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

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

        This version of this YANG module is part of RFC XXXX
        (https://datatracker.ietf.org/html/rfcXXXX); see the RFC itself
        for full legal notices.";

      // RFC Ed.: update the date below with the date of RFC publication
      // and RFC number and remove this note.
     revision 2022-02-04 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: Node Tags in YANG Modules";
     }
     identity node-tag-type {
      description
        "Base identity for node tag type.";
     }
     identity metric {
      base node-tag-type;
      description
        "Identity for metric tag type.";
     }
     identity delay {
      base node-tag-type;
      description



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        "Identity for delay metric tag type.";
     }
     identity jitter {
      base node-tag-type;
      description
        "Identity for jitter metric tag type.";
     }
     identity loss {
      base node-tag-type;
      description
        "Identity for loss metric tag type.";
     }
     identity counter {
      base node-tag-type;
      description
        "Identity for counter metric tag type.";
     }
     identity summary {
      base node-tag-type;
      description
        "Identity for summary metric tag type.";
     }
     identity gauge {
      base node-tag-type;
      description
        "Identity for gauge metric tag type.";
     }
     identity unknown {
      base node-tag-type;
      description
        "Identity for unkown metric tag type.";
     }
     identity agg {
      base node-tag-type;
      description
        "Identity for aggregated metric tag type.";
     }
     extension node-tag {
       argument tag;
       description
         "The argument 'tag' is of type 'tag'. This extension statement
          is used by module authors to indicate node tags that should
          be added automatically by the system. As such,  the origin of
          the value for the pre-defined tags should be set to 'system'.";
     }

     augment "/tags:module-tags/tags:module" {
       description



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         "Augment the Module Tags module with node tag
          attributes.";
       container node-tags {
         description
           "Contains the list of nodes or node instances and their associated
            node tags.";
         list node {
           key "id";
           description
             "Includes a list of nodes and their associated
              node tags.";
           leaf id {
             type nacm:node-instance-identifier;
             description
               "The YANG data node name or data node instance name.";
           }
          list tags {
            key "tag";
             description
               "Lists the tags associated with the node within
                the YANG  module.

                See the IANA 'YANG node Tag Prefixes' registry
                for reserved prefixes and the IANA 'IETF YANG Data
                Node Tags' registry for IETF tags.

                The 'operational' state view of this list is
                constructed using the following steps:

                1) System tags (i.e., tags of 'system' origin) are
                   added.
                2) User configured tags (i.e., tags of 'intended'
                   origin) are added.
                3) Any tag that is equal to a masked-tag is removed.";
             reference
               "RFC XXXX: node Tags in YANG Data
                          Modules, Section 9";
           leaf tag {
             type tags:tag;
             description
               "Node tag corresponding to type of node tag.";
           }
          leaf type {
            type identityref {
            base node-tag-type;
           }
           description
             "Type of node tag.";



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           }
          }
           leaf-list masked-tag {
             type tags:tag;
             description
               "The list of tags that should not be associated with the
                node within the YANG module. The user can remove
                (mask) tags from the operational state datastore by
                adding them to this list. It is not an error to add tags
                to this list that are not associated with the data
                node within YANG  module, but they have no operational
                effect.";
           }
          }
         }
      }
     }
   <CODE ENDS>

8.  Guidelines to Model Writers

   This section updates [RFC8407] by providing text that may be regarded
   as a new subsection to Section 4 of that document.  It does not
   change anything already present in [RFC8407].

8.1.  Define Standard Tags

   A module MAY indicate, using node tag extension statements, a set of
   node tags that are to be automatically associated with node within
   the module (i.e., not added through configuration).

   module example-module-A {
     //...
     import ietf-node-tags { prefix ntags; }

     container top {
       list X {
         leaf foo {
            ntags:node-tag "ietf:summary";
         }
         leaf bar {
           ntags:node-tag "ietf:loss";
         }
       }
     }
     // ...
   }




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                  Figure 2: An Example of Data Object Tag

   The module writer can use existing standard node tags, or use new
   node tags defined in the data node definition, as appropriate.  For
   IETF standardized modules, new node tags MUST be assigned in the IANA
   registry defined in Section 9.2.

9.  IANA Considerations

9.1.  YANG Data Node Tag Prefixes Registry

   This document requests IANA to create "YANG node Tag Prefixes"
   subregistry in "YANG node Tag" registry.

   Prefix entries in this registry should be short strings consisting of
   lowercase ASCII alpha-numeric characters and a final ":" character.

   The allocation policy for this registry is Specification Required
   [RFC8126].  The Reference and Assignee values should be sufficient to
   identify and contact the organization that has been allocated the
   prefix.  There is no specific guidance for the Designated Expert and
   there is a presumption that a code point should be granted unless
   there is a compelling reason to the contrary.

   The initial values for this registry are as follows:

  +----------+----------------------------------+-----------+----------+
  | Prefix   | Description                      | Reference | Assignee |
  +----------+----------------------------------+-----------+----------+
  | ietf:    | IETF Tags allocated in the IANA  | [This     | IETF     |
  |          | IETF YANG node Tags              | document] |          |
  |          | registry                         |           |          |
  |          |                                  |           |          |
  | vendor:  | Non-registered tags allocated by | [This     | IETF     |
  |          | the module's implementer.        | document] |          |
  |          |                                  |           |          |
  | user:    | Non-registered tags allocated by | [This     | IETF     |
  |          | and for the user.                | document] |          |
  +----------+----------------------------------+-----------+----------+

                            Figure 3: Table 1

   Other standards organizations (SDOs) wishing to allocate their own
   set of tags should request the allocation of a prefix from this
   registry.






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9.2.  IETF YANG Data Node Tags Registry

   This document requests IANA to create "IETF Node Tags" subregistry in
   "YANG node Tag" registry.  This subregistry appears below "YANG node
   Tag Prefixes" registry.

   This subregistry allocates tags that have the registered prefix
   "ietf:".  New values should be well considered and not achievable
   through a combination of already existing IETF tags.

   The allocation policy for this subregistry is IETF Review [RFC8126].
   The Designated Expert is expected to verify that IANA assigned tags
   conform to Net-Unicode as defined in [RFC5198], and shall not need
   normalization.

   The initial values for this subregistry are as follows:

   +----------------------------+--------------------------+-----------+
   | Node Tag                    | Description              | Reference |
   +----------------------------+--------------------------+-----------+
   |                            |                          |           |
   | ietf:metric                |Represent metric data     | [This     |
   |                            |(e.g., ifstatistics)      | document] |
   |                            |associated with specific  |           |
   |                            |node (e.g.,               |           |
   |                            |interfaces)               |           |
   |                            |                          |           |
   | ietf:delay                 |Represents the delay metric           |
   |                            |data associated with      | [This     |
   |                            |specific node.            | document] |
   |                            |                          |           |
   | ietf:jitter                |Represents the jitter metric [This    |
   |                            |data asociated with       |document]  |
   |                            |specific node.            |           |
   |                            |                          |           |
   | ietf:loss                  |Represents the loss metric| [This     |
   |                            |data associated with      | document] |
   |                            |specific node.            |           |
   |                            |                          |           |
   | ietf:counter               |Represents any metric value           |
   |                            |associated with specific  |           |
   |                            |node that monotonically   |  [This    |
   |                            |increases over time,      | document] |
   |                            |starting from zero.       |           |
   |                            |                          |           |
   | ietf:gauge                 |Represents current        |           |
   |                            |measurements associated   | [This     |
   |                            |with specific node        |document]  |



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   |                            |that may increase,        |           |
   |                            |decrease or stay constant.|           |
   |                            |                          |           |
   | ietf:summary               |Represents the metric value [This     |
   |                            |associated with specific  | document] |
   |                            |node that measures        |           |
   |                            |distributions of discrete |           |
   |                            |events without knowing    |           |
   |                            |predefined range.         |           |
   |                            |                          |           |
   | ietf:unknown               |Represents the metric value [This     |
   |                            |associated with specific  | document] |
   |                            |node that can not         |           |
   |                            |determine the type of metric.         |
   |                            |                          |           |
   |ietf:agg                    |Relates to aggregated metric [This    |
   |                            |value associated with     | document] |
   |                            |specific node (i.e.,      |           |
   |                            |aggregated statistics)    |           |
   +----------------------------+--------------------------+-----------+

                          Figure 4: Table 2

   A data node can contain one or multiple node tags.Data node to be
   tagged with the initial value in Table 2 can be one of 'container',
   'leaf-list', 'list', or 'leaf' data node.  All tag values described
   in Table 2 can be inherited down the containment hierarchy if Data
   nodes tagged with those tag values is one of 'container', 'leaf-
   list', 'list'.

9.3.  Updates to the IETF XML Registry

   This document registers the following namespace URI in the "ns"
   subregistry within the "IETF XML Registry" [RFC3688]:

      URI: urn:ietf:params:xml:ns:yang:ietf-node-tags
      Registrant Contact: The IESG.
      XML: N/A; the requested URI is an XML namespace.

9.4.  Updates to the YANG Module Names Registry

   This document registers the following YANG module in the YANG Module
   Names registry [RFC6020] within the "YANG Parameters" registry:








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      name: ietf-node-tags
      namespace: urn:ietf:params:xml:ns:yang:ietf-node-tags
      prefix: ntags
      reference: RFC XXXX
      maintained by IANA: N

10.  Security Considerations

   The YANG module specified in this document defines 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, e.g., the presence of tags
   may reveal information about the way in which data nodes or node
   instances are used and therefore providing access to private
   information or revealing an attack vector should be restricted.  Note
   that appropriate privilege and security levels need to be applied to
   the addition and removal of user tags to ensure that a user receives
   the correct data.

   This document adds the ability to associate node tag with data nodes
   or instances of data nodes within the YANG modules.  This document
   does not define any actions based on these associations, and none are
   yet defined, and therefore it does not by itself introduce any new
   security considerations.

   Users of the node tag meta-data may define various actions to be
   taken based on the node tag meta-data.  These actions and their
   definitions are outside the scope of this document.  Users will need
   to consider the security implications of any actions they choose to
   define, including the potential for a tag to get 'masked' by another
   user.

11.  Acknowledgements

   The authors would like to thank Ran Tao for his major contributions
   to the initial modeling and use cases.







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   The authors would also like to acknowledge the comments and
   suggestions received from Juergen Schoenwaelder, Andy Bierman, Lou
   Berger,Jaehoon Paul Jeong, Wei Wang, Yuan Zhang, Ander Liu, YingZhen
   Qu, Boyuan Yan, Adrian Farrel, and Mahesh Jethanandani.

12.  Contributors

         Liang Geng
         Individual
         32 Xuanwumen West St, Xicheng District
         Beijing  10053

13.  References

13.1.  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>.

   [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>.

   [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>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [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>.





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   [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>.

   [RFC8407]  Bierman, A., "Guidelines for Authors and Reviewers of
              Documents Containing YANG Data Models", BCP 216, RFC 8407,
              DOI 10.17487/RFC8407, October 2018,
              <https://www.rfc-editor.org/info/rfc8407>.

   [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>.

   [RFC8819]  Hopps, C., Berger, L., and D. Bogdanovic, "YANG Module
              Tags", RFC 8819, DOI 10.17487/RFC8819, January 2021,
              <https://www.rfc-editor.org/info/rfc8819>.

13.2.  Informative References

   [FCAPS]    International Telecommunication Union, "X.700 : Management
              framework for Open Systems Interconnection (OSI) for CCITT
              applications",  , September 1992,
              <http://www.itu.int/rec/T-REC-X.700-199209-I/en>.

   [RFC5198]  Klensin, J. and M. Padlipsky, "Unicode Format for Network
              Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008,
              <https://www.rfc-editor.org/info/rfc5198>.

   [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>.

   [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>.

   [RFC7952]  Lhotka, L., "Defining and Using Metadata with YANG",
              RFC 7952, DOI 10.17487/RFC7952, August 2016,
              <https://www.rfc-editor.org/info/rfc7952>.






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   [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>.

   [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>.

   [RFC8526]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "NETCONF Extensions to Support the Network
              Management Datastore Architecture", RFC 8526,
              DOI 10.17487/RFC8526, March 2019,
              <https://www.rfc-editor.org/info/rfc8526>.

   [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>.

   [RFC8792]  Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
              "Handling Long Lines in Content of Internet-Drafts and
              RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
              <https://www.rfc-editor.org/info/rfc8792>.

   [RFC9195]  Lengyel, B. and B. Claise, "A File Format for YANG
              Instance Data", RFC 9195, DOI 10.17487/RFC9195, February
              2022, <https://www.rfc-editor.org/info/rfc9195>.

   [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>.

Appendix A.  Example: Additional Auxiliary Data Property Information

   This section gives an example of how Auxiliary Data Property Module
   could be defined.  It demonstrates how auxiliary data property
   configuration parameters can be conditionally augmented to the
   generic node list.  The example is not intended as a complete module
   for Auxiliary Data Property configuration.






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  module ex-auxiliary-data-property {
    yang-version 1.1;
     namespace "http://example.com/auxiliary-data-property";
     prefix "dp";

     import ietf-module-tags {
       prefix tags;
     }
     import ietf-node-tags {
       prefix ntags;
     }
     identity critical {
      base ntags:node-tag-type;
      description
      "Identity for critical node tag type.";
     }
     augment "/tags:module-tags/tags:module/ntags:node-tags/ntags:"
       + "node/ntags:tags" {
       when 'derived-from-or-self(ntags:type, "dp:critical")';
       description "Extend ietf-node-tags module for auxiliary data property.";
       leaf value {
         type string;
           description
           "The auxiliary information corresponding
            to data node instance tagged with 'critical'
            node tag type.";
       }
       // other auxiliary data property config params, etc.
     }
   }

Appendix B.  Instance Level Tunnel Tagging Example

   In the example shown in the following figure,the 'tunnel-svc' data
   node is a list node defined in a 'example-tunnel-pm' module and has 7
   child nodes: 'name','create-time','modified-time','average-
   latency','packet-loss','min-latency','max-latency' leaf node.  In
   these child nodes, the 'name' leaf node is the key leaf for the
   'tunnel-svc' list.  Following is the tree diagram [RFC8340] for the
   "example-tunnel-pm" module:











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           +--rw tunnel-svc* [name]
           |   +--rw name                      string
           |   +--ro create-time               yang:date-and-time
           |   +--ro modified-time             yang:date-and-time
           |   +--ro average-latency           yang:gauge64
           |   +--ro packet-loss               yang:counter64
           |   +--ro min-latency               yang:gauge64
           |   +--ro max-latency               yang:gauge64

   To help identify specific data for a customer, users tags on specific
   instances of the data nodes are created as follows:

    <rpc message-id="103"
         xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
      <edit-data xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-nmda"
                 xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
        <datastore>ds:running</datastore>
        <config>
        <module-tag>
         <module>
         <name>example-tunnel-pm</name>
          <node-tags
            xmlns="urn:ietf:params:xml:ns:yang:ietf-node-tags">
          <node>
            <id>
             /tp:tunnel-svc[name='foo']/tp:packet-loss
            </id>
            <tags>
            <tag>user:customer1_example_com</tag>
            </tags>
            <tags>
            <tag>ietf:critical</tag>
            </tags>
          </node>
          <node>
            <id>
              /tp:tunnel-svc[name='bar']/tp:modified-time
           </id>
            <tags>
            <tag>user:customer2_example_com</tag>
            </tags>
          </node>
        </node-tags>
       </module>
       </module-tag>
        </config>
      </edit-data>
    </rpc>



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   Note that the 'ietf:critical' tag is addtional new tag value that
   needs to be allocated from "IETF Node Tags" subregistry in
   Section 9.2.

Appendix C.  NETCONF Example

   The following is a NETCONF example result from a query of node tags
   list.  For the sake of brevity only a few module and associated data
   node results are provided.  The example uses the folding defined in
   [RFC8792].









































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 =============== NOTE: '\' line wrapping per RFC 8792 ================

 <ns0:data xmlns:ns0="urn:ietf:params:xml:ns:netconf:base:1.0">
  <t:module-tags xmlns:t="urn:ietf:params:xml:ns:yang:ietf-module-tags">
     <t:module>
        <t:name>ietf-interfaces</t:name>
        <s:node-tags
          xmlns:s="urn:ietf:params:xml:ns:yang:ietf-node-tags">
         <s:node>
          <s:id>
           /if:interfaces/if:interface/if:statistics/if:in-errors
          </s:id>
          <s:tags>
          <s:tag>ietf:metric</s:tag>
          </s:tags>
          <s:tags>
          <s:tag>ietf:loss</s:tag>
          </s:tags>
          <s:tags>
          <s:tag>ietf:agg</s:tag>
          </s:tags>
         </s:node>
       </s:node-tags>
     </t:module>
     <t:module>
        <t:name>ietf-ip</t:name>
        <s:node-tags
          xmlns:s="urn:ietf:params:xml:ns:yang:ietf-node-tags">
         <s:node>
         <s:id>/if:interfaces/if:interface/ip:ipv4/ip:mtu</s:id>
         <s:tags>
         <s:tag>ietf:metric</s:tag>
         </s:tags>
        </s:node>
       </s:node-tags>
     </t:module>
   </t:module-tags>
 </ns0:data>

                 Figure 5: Example NETCONF Query Output

Appendix D.  Non-NMDA State Module

   As per [RFC8407], the following is a non-NMDA module to support
   viewing the operational state for non-NMDA compliant servers.






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   <CODE BEGINS> file "ietf-node-tags-state@2022-02-03.yang"
   module ietf-node-tags-state {
     yang-version 1.1;
     namespace
           "urn:ietf:params:xml:ns:yang:ietf-node-tags-state";
     prefix ntags-s;

     import ietf-netconf-acm {
       prefix nacm;
       reference
       "RFC 8341: Network Configuration Access Control
                  Model";
     }
     import ietf-module-tags {
       prefix tags;
     }
     import ietf-module-tags-state {
       prefix tags-s;
       reference
       "RFC 8819: YANG Module Tags ";
     }
     organization
       "IETF NetMod Working Group (NetMod)";

     contact
      "WG Web: <https://datatracker.ietf.org/wg/netmod/>
       WG List:<mailto:netmod@ietf.org>

       Editor: Qin Wu
               <mailto:bill.wu@huawei.com>

       Editor: Benoit Claise
               <mailto:benoit.claise@huawei.com>

       Editor: Peng Liu
               <mailto:liupengyjy@chinamobile.com>

       Editor: Zongpeng Du
               <mailto:duzongpeng@chinamobile.com>

       Editor: Mohamed Boucadair
               <mailto:mohamed.boucadair@orange.com>";
      // RFC Ed.: replace XXXX with actual RFC number and
      // remove this note.
     description
       "This module describes a mechanism associating data node
        tags with YANG data node within YANG modules. Tags may be
        IANA assigned or privately defined.



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

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

        This version of this YANG module is part of RFC XXXX
        (https://datatracker.ietf.org/html/rfcXXXX); see the RFC
        itself for full legal notices.";

      // RFC Ed.: update the date below with the date of RFC publication
      // and RFC number and remove this note.
     revision 2022-02-04 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: Node Tags in YANG Data
                    Modules";
     }
     identity node-tag-type {
      description
        "Base identity for node tag type.";
     }
     augment "/tags-s:module-tags-state/tags-s:module" {
       description
         "Augments the Module Tags module with node tag
          attributes.";
       container node-tags {
         config false;
         status deprecated;
         description
           "Contains the list of data nodes and their
            associated self describing tags.";
         list node {
           key "id";
           status deprecated;
           description
             "Lists the data nodes and their associated self
              describing tags.";
           leaf id {
             type nacm:node-instance-identifier;
             mandatory true;
             status deprecated;
             description



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               "The YANG data node name.";
           }
          list tags {
             key "tag";
             status deprecated;
             description
               "Lists the tags associated with the data node within
                the YANG  module.

                See the IANA 'YANG node Tag Prefixes' registry
                for reserved prefixes and the IANA 'IETF YANG Data
                Node Tags' registry for IETF tags.

                The 'operational' state view of this list is
                constructed using the following steps:

                1) System tags (i.e., tags of 'system' origin) are
                   added.
                2) User configured tags (i.e., tags of 'intended'
                   origin) are added.
                3) Any tag that is equal to a masked-tag is removed.";
             reference
               "RFC XXXX: Node Tags in YANG Data
                          Modules, Section 9";
           leaf tag {
             type tags:tag;
             status deprecated;
             description
               "Node tag corresponding to type of node tag.";
            }
           leaf type {
            type identityref {
            base node-tag-type;
            }
           status deprecated;
           description "type of the node tag.";
           }
        }
           leaf-list masked-tag {
             type tags:tag;
             status deprecated;
             description
               "The list of tags that should not be associated with the
                data node within the YANG module. The user can remove
                (mask) tags from the operational state datastore by
                adding them to this list. It is not an error to add
                tags to this list that are not associated with the
                data node within YANG module, but they have no



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                operational effect.";
           }
         }
       }
     }
   }
   <CODE ENDS>

Appendix E.  Targeted Data Fetching Example

   The following provides tagged data node Fetching example.  The
   subscription "id" values of 22 used below is just an example.  In
   production, the actual values of "id" might not be small integers.

   +-----------+                        +-----------+
   | Subscriber|                        | Publisher |
   +-----+-----+                        +-----+-----+
         |                                    |
         |      Node Tagging Fetching         |
         |    (id, node-tag = metric)         |
         |<-----------------------------------+
         |                                    |
         |     establish-subscription         |
         +----------------------------------->|
         |                                    |
         |       RPC Reply: OK, id = 22       |
         |<-----------------------------------+
         |                                    |
         |    Notification Message (for 22)   |
         |<-----------------------------------+
         |                                    |

   The subscriber can query node tag list from operational datastore in
   the network device using "ietf-node-tags" module defined in this
   document and fetch tagged data node instances and associated data
   path to the datastore node.  The node tag information instruct the
   receiver to subscribe tagged data node (e.g., performance metric data
   nodes) using standard subscribed notification mechanism [RFC8639].













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   =============== NOTE: '\' line wrapping per RFC 8792 ================

   <?xml version="1.0" encoding="UTF-8"?>
       <t:module-tags
         xmlns:t="urn:ietf:params:xml:ns:yang:ietf-module-tags">
          <t:module>
             <t:name>ietf-interfaces</t:name>
             <s:node-tags
               xmlns:s="urn:ietf:params:xml:ns:yang:ietf-node-tags">
              <s:node>
               <s:id>/if:interfaces/if:interface/if:in-errors</s:id>
               <s:tags>
               <s:tag>ietf:metric</s:tag>
               </s:tags>
               <s:tags>
               <s:tag>ietf:loss</s:tag>
               </s:tags>
              </s:node>
              </s:node-tags>
         </t:module>
       </module-tags>

                 Figure 6: List of Available Target Objects


   With node tag information returned,e.g., in the 'get-data' operation,
   the subscriber identifies tagged data node and associated data path
   to the datastore node and sends a standard establish-subscription RPC
   [RFC8639] to subscribe tagged data nodes that are interests to the
   client application from the publisher.  The publisher returns
   specific data node types of operational state (e.g., in-errors
   statistics data) subscribed by the client as follows:



















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   =============== NOTE: '\' line wrapping per RFC 8792 ================

    <netconf:rpc message-id="101"
        xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
      <establish-subscription
          xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifica\
          tions"
          xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
        <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">
          /if:interfaces/if:interface/if:statistics/if:in-errors
        </yp:datastore-xpath-filter>
        <yp:periodic>
          <yp:period>500</yp:period>
        </yp:periodic>
      </establish-subscription>
    </netconf:rpc>

Appendix F.  Changes between Revisions

   Editorial Note (To be removed by RFC Editor)

   v07 - v08

   *  Make objective clearly, cover tags for both nodes in the schema
      tree and nodes in the data tree.

   *  Document clearly which tags can be cached and how applications are
      supposed to resynchronize and pull in any update in section 3.

   *  Clarify Instance level tag is not used to guide retrieval
      operations in section 3.

   *  Distinguish Instance level tag from Metadata annotation in the
      introduction section.

   *  Distinguish Schema Level tag from Instance level tag in the
      introduction section and section 3.

   *  Schema Level tag used in xpath query has be clarified in section
      3.

   *  Other editorial changes.




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   v06 - v07

   *  Update use case in section 3 to remove object and subobject
      concept and massive related words.

   *  Change the title into Node Tags in YANG Modules.

   *  Update Model Tag design in section 5.1 based on Balazs's comments.

   *  Add Instance level tunnel tagging example in the Appendix.

   *  Add 'type' parameter in the base model and add one more model
      extension example in the Appendix.

   *  Consolidate opm-tag extension, metric-type extension and multi-
      source-tag extension into one generic yang extension.

   *  Remove object tag and property tag.

   *  Other Appendix Updates.

   v05 - v06

   *  Additional Editorial changes;

   *  Use the folding defined in [RFC8792].

   v04 - v05

   *  Add user tag formating clarification;

   *  Provide guidance to the Designated Expert for evaluation of YANG
      node Tag registry and YANG node Tag prefix registry.

   *  Update the figure 1 and figure 2 with additional tags.

   *  Security section enhancement for user tag managment.

   *  Change data node name into name in the module.

   *  Other Editorial changes to address Adrian's comments and comments
      during YANG docotor review.

   *  Open issue: Are there any risks associated with an attacker adding
      or removing tags so that a requester gets the wrong data?

   v03 - v04




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   *  Remove histogram metric type tag from metric type tags.

   *  Clarify the object tag and property tag,metric tag are mutual
      exlusive.

   *  Clarify to have two optional node tags (i.e.,object tag and
      property tag) to indicate relationship between data nodes.

   *  Update targeted data node collection example.

   v02 - v03

   *  Additional Editorial changes.

   *  Security section enhancement.

   *  Nits fixed.

   v01 - v02

   *  Clarify the relation between data node, object tag, property tag
      and metric tag in figure 1 and figure 2 and related description;

   *  Change Metric Group into Metric Type in the YANG model;

   *  Add 5 metric types in section 7.2;

   v00 - v01

   *  Merge node tag use case section into introduction section as a
      subsection;

   *  Add one glossary section;

   *  Clarify the relation between data node, object tag, property tag
      and metric tag in node Tags Use Case section;

   *  Add update to RFC8407 in the front page.

Authors' Addresses

   Qin Wu
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing
   Jiangsu, 210012
   China
   Email: bill.wu@huawei.com



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Internet-Draft               YANG Node Tags                    June 2022


   Benoit Claise
   Huawei
   De Kleetlaan 6a b1
   1831 Diegem
   Belgium
   Email: benoit.claise@huawei.com


   Peng Liu
   China Mobile
   32 Xuanwumen West St, Xicheng District
   Beijing
   Email: liupengyjy@chinamobile.com


   Zongpeng Du
   China Mobile
   32 Xuanwumen West St, Xicheng District
   Beijing
   Email: duzongpeng@chinamobile.com


   Mohamed Boucadair
   Orange
   35000 Rennes
   France
   Email: mohamed.boucadair@orange.com
























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