NETMOD Working Group                                               Q. Wu
Internet-Draft                                                 B. Claise
Updates: 8407 (if approved)                                       Huawei
Intended status: Standards Track                                  P. Liu
Expires: 14 August 2022                                            Z. Du
                                                            China Mobile
                                                            M. Boucadair
                                                                  Orange
                                                        10 February 2022


                    Self-Describing Data Object Tags
                     draft-ietf-netmod-node-tags-05

Abstract

   This document defines a method to tag data objects associated with
   operation and management data in YANG modules.  The expectation is
   for this YANG data object tagging method to be used to classify data
   objects from different YANG modules and identify their
   characteristics data.  Tags may be registered as well as assigned
   during the module definition, assigned by implementations, or
   dynamically defined and set by users.  This document also provides
   guidance to future 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 14 August 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
     2.1.  Requirements Notation . . . . . . . . . . . . . . . . . .   4
     2.2.  Glossary  . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Self-Describing Data Object Tags: Massive Data Object
           Collection Use Case . . . . . . . . . . . . . . . . . . .   4
   4.  Data Object Tag Values  . . . . . . . . . . . . . . . . . . .   7
     4.1.  IETF Tags . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.2.  Vendor Tags . . . . . . . . . . . . . . . . . . . . . . .   7
     4.3.  User Tags . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.4.  Reserved Tags . . . . . . . . . . . . . . . . . . . . . .   8
   5.  Data Object Tag Management  . . . . . . . . . . . . . . . . .   8
     5.1.  Module Design Tagging . . . . . . . . . . . . . . . . . .   8
     5.2.  Implementation Tagging  . . . . . . . . . . . . . . . . .   9
     5.3.  User Tagging  . . . . . . . . . . . . . . . . . . . . . .   9
   6.  Data Object Tags Module Structure . . . . . . . . . . . . . .   9
     6.1.  Data Object Tags Module Tree  . . . . . . . . . . . . . .   9
   7.  YANG Module . . . . . . . . . . . . . . . . . . . . . . . . .  10
   8.  Guidelines to Model Writers . . . . . . . . . . . . . . . . .  13
     8.1.  Define Standard Tags  . . . . . . . . . . . . . . . . . .  13
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  YANG Data Object Tag Prefixes Registry  . . . . . . . . .  14
     9.2.  IETF YANG Data Object Tags Registry . . . . . . . . . . .  14
     9.3.  Updates to the IETF XML Registry  . . . . . . . . . . . .  16
     9.4.  Updates to the YANG Module Names Registry . . . . . . . .  17
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  17
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  18
   12. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  18
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  18
     13.2.  Informative References . . . . . . . . . . . . . . . . .  19
   Appendix A.  NETCONF Example  . . . . . . . . . . . . . . . . . .  20
   Appendix B.  Non-NMDA State Module  . . . . . . . . . . . . . . .  22
   Appendix C.  Targeted data object collection example  . . . . . .  25
   Appendix D.  Changes between Revisions  . . . . . . . . . . . . .  28
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  29




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1.  Introduction

   As described in [RFC8819], the use of tags for classification and
   organization is fairly ubiquitous not only within IETF protocols, but
   in the Internet itself (e.g., "#hashtags").  As a reminder, a module
   tag defined in [RFC8819] is a string associated with a module name at
   the module level.

   Many data models have been specified by various 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 objects defined by these technology-specific data
   models might represent a portion of fault, configuration, accounting,
   performance, and security (FCAPS) management information at different
   locations and categorised in various different ways.  Further, there
   is no consistent classification criteria or representation for a
   specific service, feature, or data source.

   This document defines self-describing data object tags and associates
   them with data objects within a YANG module, which:

   *  Provide dictionary meaning for specific targeted data objects.

   *  Indicate a relationship between data objects within the same YANG
      module or from different YANG modules.

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

   The self-describing data object tags can be used by the NETCONF/
   RESTCONF client to classify data objects from different YANG modules
   and identify characteristic data.  In addition, they can provide
   input, instructions, indications to selection filters and filter
   queries of configuration or operational state on a server based on
   these data object tags, e.g., return specific objects containing
   operational state related to system-management.  NETCONF clients can
   discover data objects with self-describing data object tags supported
   by a NETCONF server by means of the <get-schema> operation.  The
   self-describing data object tag capability can also be advertised
   using the capability notification model [I-D.netconf-notification-
   capabilities] by the NETCONF server or some websites where offline
   documents are kept.  Similar to YANG module tags defined [RFC8819],
   these data object tags may be registered or assigned during the
   module definition, assigned by implementations, or dynamically
   defined and set by users.






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   This document defines a YANG module [RFC7950] which augments the
   module tag model [RFC8819] and provides a list of data object entries
   to allow for adding or removing of self-describing tags as well as
   viewing the set of self-describing tags associated with specific data
   objects within YANG modules.

   This document defines three extension statements to be used to
   indicate self-describing tags that should be added by the module
   implementation automatically (i.e., outside of configuration).

   This document also defines an IANA registry for tag prefixes as well
   as 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].

   The meaning of the symbols can be found in [RFC8340].

2.  Terminology

2.1.  Requirements Notation

   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.

2.2.  Glossary

   OPM   Object, Property, Metric

   FCAPS  Fault, Capability, Accouting, Performance and Security

3.  Self-Describing Data Object Tags: Massive Data Object Collection Use
    Case

   Among data object tags, the 'opm' (object, property, metric) tags can
   be used to tackle massive data object collections, indicate
   relationships between data objects, and capture YANG data objects
   associated with performance metrics data modelled with YANG (as shown
   in Figure 1).






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                     /----\
                    /Object\
                    | Tag  |
                     \- +-/
                        |
              +---------V--------+    contain
              | YANG Data Node   <----------------+
              | /Data Object 1   |                |
              +--^-------------^-+                |
                 |contain      |contain           |
                 |             |                  |
     +-----------+---+ +- -----+-------+    +-----+---------+
     | YANG Data Node| | YANG Data Node|    | YANG Data Node|
     |/Sub Object 2  | | /Sub Object 3 |    | /Sub Object 4 |
     +-^-------------+ +^------^-------+    +^------^-----^-+
       |                |      |             |      |     |
       |                |    /-+-\           |    /-+-\   |
     /-+--\             |  /Metric \         |  /Metric \ |
    Property            |  |  Tag  |         |  |  Tag  | |
    \ Tag  /            |    \- -/           |    \- -/   |
     \----/             |                    |            |
                        |                    |            |
                        |                    |            |
                      /----\                 |            |
                     /Metric\              /-+--\      /-----\
                    |  Type  |            /Metric\   //  Multi\\
                     \  Tag /            |  Type  | |   Source  |
                      \- --/              \  Tag /   \\  Tag  //
                                           \- --/      \-----/

        Figure 1: The Relation between Object, Property, and Metric

   In Figure 1, data objects can contain other data objects called
   subobjects.  Both object and subobjects can be modeled as YANG data
   nodes [RFC7950].  Data objects that contain other data objects can be
   one of type 'container', 'leaf-list', and 'list' and are tagged with
   the object tag.  A subobject tagged with the property tag is a 'leaf'
   node.  Subobjects tagged with the metric tag can be one of
   'container', 'leaf-list', 'list', or 'leaf' data node.

   A data object may contain one single object tag, or one single
   property tag, or one single metric tag.  The data object tagged with
   the metric tag also can have one or multiple Metric Type tags and/or
   one single multi-source tag.

   The use of 'opm' tags is meant to help filter discrete categories of
   YANG data objects scattered across the same or different YANG modules
   supported by a device and capture all network performance data or all



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   property data in a single view of the data.  In Figure 2, the
   'tunnel-svc' data object is a container node defined in the 'tunnel-
   pm' module and can be seen as the root object for property tagged
   subobjects (e.g., 'tunnel-svc'/'create-time') and metric tagged
   subobjects (e.g., 'tunnel-svc'/'avg-latency').  The 'name', 'create-
   time', and 'modified-time' are property tagged subobjects under
   'tunnel-svc' container.  The 'avg-latency' and 'packet-loss' metrics
   are tagged subobjects under 'tunnel-svc' container node.  Consider
   the 'tunnel-svc' data object and the tunnel-svc/name data object as
   an example: the 'tunnel-svc' data object has one single object tag
   (i.e., 'ietf:object') while the tunnel-svc/name data object has one
   single property subobject tag (i.e., 'ietf:property').  In addition,
   not all metric subobjects need to be tagged, e.g., specific
   categories, such as loss-related metric subobjects, need to be tagged
   with a metric-type tag which can further reduce amount data to be
   fetched.

 +------------------------+--------------------------------+-----------+
 |      Data              |  Object    Property     Metric |  Multi-   |
 |      Object            |   Tag        Tag         Tag   |Source Tag |
 +------------------------+--------------------------------+-----------+
 |                        |  ietf:                         |           |
 |tunnel-svc              |  object                        |           |
 |                        |            ietf:               |           |
 |tunnel-svc/name         |            property            |           |
 |                        |            ietf:               |           |
 |tunnel-svc/create-time  |            property            |           |
 |                        |            ietf:               |           |
 |tunnel-svc/modified-time|            property            |           |
 |                        |                                |           |
 |tunnel-svc/avg-latency  |                        ietf:   | non-agg   |
 |                        |                        metric  |           |
 |tunnel-svc/packet-loss  |                        ietf:   | non-agg   |
 |                        |                        metric  |           |
 |tunnel-svc/min-latency  |                        ietf:   | non-agg   |
 |                        |                        metric  |           |
 |tunnel-svc/max-latency  |                        ietf:   | non-agg   |
 |                        |                        metric  |           |
 +------------------------+--------------------------------+-----------+

         Figure 2: Example of OPM Tags Used in the YANG Module

   If data objects in YANG modules are suitably tagged and learnt by the
   client from a live server, the client can retrieve paths to all
   targeted data objects and then use an XPath query defined
   [RFC8639][RFC8641] to list all tagged data objects which reflect
   network characteristics.




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4.  Data Object Tag Values

   All data object tags SHOULD begin with a prefix indicating who owns
   their definition.  An IANA registry (Section 9.1) is used to support
   registering data object tag prefixes.  Currently, 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.

   Again, 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 data object tag that has the prefix "ietf:".

   All IETF data object tags are registered with IANA in a registry
   defined Section 9.2 later in this document (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.  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:example.com:vendor-defined-classifier).

4.3.  User Tags

   A user tag is any tag that has the prefix "user:".  For the avoidance
   of confusion, the colon (":") when it appears for the first time, is
   always assumed to be the separator between a prefix and the rest of
   the tag.  And so, when a user tag does not have a prefix, it MUST NOT
   contain a colon.

   These tags are defined by the user/administrator and are not meant to
   be registered.  Users are not required to use the "user:" prefix;
   however, doing so is RECOMMENDED as it helps avoid collisions.






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4.4.  Reserved Tags

   Any tag not starting with the prefix "ietf:", "vendor:" or "user:"
   (Section 9.1 ) is reserved for future use.  These tag values are not
   invalid, but simply reserved in the context of specifications (e.g.,
   RFCs).

5.  Data Object Tag Management

   Tags may be associated with a data object 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
   data object tags are users, users may also remove any tag from a live
   server, no matter how the tag became associated with a data object
   within a YANG module.

5.1.  Module Design Tagging

   A data object definition MAY indicate a set of data object tags to be
   added by a module's implementer.  These design time tags are
   indicated using a set of extension statements which include:

   opm-tag extension statement:  Classifies management and operation
      data into object, property subobject, and metric subobject
      categories.  Both object and subobjects can be modeled as YANG
      data nodes [RFC7950].  Data objects that contain other data
      objects can be one of type 'container', 'leaf-list', and 'list'
      and are tagged with object tag.  A subobject tagged with the
      property tag is a 'leaf' node.  Subobjects tagged with the metric
      tag can be one of 'container', 'leaf-list', 'list', or 'leaf' data
      node.  A data object contains one single object tag, one single
      property tag, or one single metric tag.  A data object tagged with
      metric tag also can have one or multiple Metric type tag and/or
      one single multi-source tag.  See the examples depicted in
      Figure 2 and Figure 4.

   metric-type extension statement:  Provides metric data objects
      classifications (e.g., loss, jitter, delay, counter, gauge,
      summary, unknown) within the YANG module.

   multi-source-tag extension statement:  Identifies multi-source
      aggregation type (e.g., aggregated, non-aggregated) related to a
      metric subobject.  The 'aggregated' multi-source aggregation type
      allows a large number of measurements on metric subobjects from
      different sources of the same type (e.g., line card, each
      subinterface of aggregated Ethernet interface) to be combined into
      aggregated statistics and report as one metric subobject.  The



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      'non-aggregated' multi-source aggregation type allows measurement
      from each source of the same type (e.g., line card, each
      subinterface of aggregated Ethernet interface) to be reported
      separately.

   Among these extension statements, the metric-type and multi-source
   tag extension statements are context information that can be used to
   correlate data objects from the different modules.

   If the data node is defined in an IETF standards track document, the
   data object tags MUST be IETF Tags (Section 4.1).  Thus, new data
   object 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
   object within a YANG module.  These tags SHOULD be IETF Tags (i.e.,
   registered) or vendor tags.

5.3.  User Tagging

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

6.  Data Object Tags Module Structure

6.1.  Data Object Tags Module Tree

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

   module: ietf-data-object-tags
   augment /tags:module-tags/tags:module:
     +--rw data-object-tags
        +--rw data-object* [name]
           +--rw name  nacm:node-instance-identifier
           +--rw tag*         tags:tag
           +--rw masked-tag*  tags:tag

                  Figure 3: YANG Module Tags Tree Diagram





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7.  YANG Module

   This module imports types from [RFC8819],[RFC8341].

   <CODE BEGINS> file "ietf-data-object-tags@2022-02-04.yang"
   module ietf-data-object-tags {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-data-object-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<mailto:liupengyjy@chinamobile.com>
       Editor:  Zongpeng Du<mailto:duzongpeng@chinamobile.com>
       Editor:  Mohamed Boucadair<mailto:mohamed.boucadair@orange.com>";
     description
       "This module describes a mechanism associating self-describing
        tags with YANG data object 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 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



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        (https://datatracker.ietf.org/html/rfcXXXX); see the RFC itself
        for full legal notices.";

     revision 2022-02-04 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: Self-Describing Data Object Tags";
     }

     extension opm-tag {
       argument tag;
       description
         "The argument 'tag' is of type 'tag'. This extension statement
          is used by module authors to indicate the opm tags that should
          be added automatically by the system. 'opm-tag' is used to
          classify operation and management data objects into the three
          categories, object, property, and metric. Data Object can
          contain other data objects called subobjects. Both object and
          subobjects can be modeled as data nodes. The Data Object
          tagged with object tag can be one of container, leaf-list and
          list. The Data Object tagged with the Property tag is a leaf
          node. The Data Object tagged with the Metric tag can be one of
          container, leaf-list, list, leaf. The Data objects tagged with
          either property tag or metric tag are subobjects belonging to
          a specific root data object. Each Data Object may contain one
          single object tag, or one single property tag, or one single
          metric tag (these tags are mutually exclusive). As such, the
          origin of the value for the pre-defined tags should be set to
          'system'.";
     }

     extension metric-type {
       argument tag;
       description
         "The argument 'tag' is of type 'tag'. The metric type can be
          used to provide metric data object classification
          (e.g., loss, jitter, packet loss,counter, gauge,
          summary, unknown) within the YANG module.";
     }

     extension multi-source-tag {
       argument tag;
       description
         "The argument 'tag' is of type 'tag'. The multi-source-tag can be
          used to identify multi-source aggregation type(e.g.,aggregated,
          non-aggregated) related to a metric subobject.




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         The 'aggregated' multi-source aggregation type allows a large
         number of measurements on metric subobjects from different sources
         of the same type (e.g., line card, each subinterface of aggregated
         Ethernet interface) to be combined into aggregated statistics and
         reported as one metric subobject value. The 'non-aggregated'
         multi-source aggregation type allows measurement from each source
         of the same type (e.g., line card, each subinterface of aggregated
         Ethernet interface) to be reported separately.";
      }

     augment "/tags:module-tags/tags:module" {
       description
         "Augment the Module Tags module with data object tag attributes";
       container data-object-tags {
         description
           "Contains the list of data objects and their associated data
            object tags";
         list data-object {
           key "name";
           description
             "A list of data objects and their associated data object tags";
           leaf name {
             type nacm:node-instance-identifier;
             mandatory true;
             description
               "The YANG data object name.";
           }
           leaf-list tag {
             type tags:tag;
             description
               "Tags associated with the data object within the YANG module.
                See the IANA 'YANG Data Object Tag Prefixes' registry for
                reserved prefixes and the IANA 'IETF YANG Data Object 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.";
           }
           leaf-list masked-tag {
             type tags:tag;
             description
               "The list of tags that should not be associated with the data
                object within the YANG module. The user can remove (mask)



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                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 object within YANG
                module, but they have no operational effect.";
           }
         }
       }
     }
   }
   <CODE ENDS>

8.  Guidelines to Model Writers

   This section updates [RFC8407].

8.1.  Define Standard Tags

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

    module example-module-A {
           //...
           import ietf-data-node-tags { prefix ntags; }
           container top {
             ntags:opm-tag "ietf:object";
            list X {
              leaf foo {
              ntags:opm-tag "ietf:property";
               }
             leaf bar {
             ntags:opm-tag "ietf:metric";
             }
         }
       }
     // ...
    }

                     Figure 4: Data object tag example

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

9.  IANA Considerations




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9.1.  YANG Data Object Tag Prefixes Registry

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

   This registry allocates tag prefixes.  All YANG Data Object Tags
   should begin with one of the prefixes in this 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 Data Object 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 5: Table 1

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

9.2.  IETF YANG Data Object Tags Registry

   This document requests IANA to create "IETF OPM Tags","IETF Metric
   Type Tags","IETF Multiple Source Tags" three subregistries in "YANG
   Data Object Tag" registry.  These 3 subregistries appear below "YANG
   Data Object Tag Prefixes" registry.





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   Three subregistries allocate 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 these three subregistries 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 these three subregistries are as follows:

   +----------------------------+--------------------------+-----------+
   | OPM Tag                    | Description              | Reference |
   +----------------------------+--------------------------+-----------+
   |                            |                          |           |
   | ietf:object                |Represents Root object    | [This     |
   |                            |containing other data     |document]  |
   |                            |objects (e.g., interfaces)|           |
   |                            |                          |           |
   | ietf:property              |Represents a property     | [This     |
   |                            |data object(e.g., ifindex)| document] |
   |                            |associated with a specific|           |
   |                            |root object (e.g.,        |           |
   |                            |interfaces)               |           |
   |                            |                          |           |
   | ietf:metric                |Represent metric data     | [This     |
   |                            |object(e.g., ifstatistics)| document] |
   |                            |associated with specific  |           |
   |                            |root object(e.g.,         |           |
   |                            |interfaces)               |           |
   +----------------------------+--------------------------+-----------+
   +----------------------------+--------------------------+-----------+
   | Metric Type Tag           | Description               | Reference |
   +----------------------------+--------------------------+-----------+
   | ietf:delay                 |Represents the delay metric           |
   |                            |group to which the metric | [This     |
   |                            |data objects belong to.   | document] |
   |                            |                          |           |
   | ietf:jitter                |Represents the jitter metric [This    |
   |                            |group to which the metric |document]  |
   |                            |data objects belong to.   |           |
   |                            |                          |           |
   | ietf:loss                  |Represents the loss metric| [This     |
   |                            |group to which the metric | document] |
   |                            |data objects belong to.   |           |
   |                            |                          |           |
   | ietf:counter               |Represents any metric value           |
   |                            |associated with a metric  |           |



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   |                            |data object that monotonically[This   |
   |                            |increases over time,      | document] |
   |                            |starting from zero.       |           |
   |                            |                          |           |
   | ietf:gauge                 |Represents current        |           |
   |                            |measurements associated   | [This     |
   |                            |with a metric data object |document]  |
   |                            |that may increase,        |           |
   |                            |decrease or stay constant.|           |
   |                            |                          |           |
   | ietf:summary               |Represents the metric value [This     |
   |                            |associated with a metric  | document  |
   |                            |data object that measures |           |
   |                            |distributions of discrete |           |
   |                            |events without knowing    |           |
   |                            |predefined range.         |           |
   |                            |                          |           |
   | ietf:unknown               |Represents the metric value [This     |
   |                            |associated with metric    | document  |
   |                            |data object that can not  |           |
   |                            |determine the type of metric.         |
   +----------------------------+--------------------------+-----------+

   +----------------------------+--------------------------+-----------+
   | Multiple Source Tag        | Description              | Reference |
   +----------------------------+--------------------------+-----------+
   |ietf:agg                    |Relates to multiple sources [This     |
   |                            |aggregation type (i.e.,   | document] |
   |                            |aggregated statistics)    |           |
   |                            |                          |           |
   |ietf:non-agg                |Relates to multiple sources [This     |
   |                            |aggregation type (i.e.,   | document] |
   |                            |non-aggregated statistics)|           |
   +----------------------------+--------------------------+-----------+

                          Figure 6: Table 2

9.3.  Updates to the IETF XML Registry

   This document requests IANA to register a new URI in the "IETF XML
   Registry" [RFC3688].  Following the format in [RFC3688], the
   following registration has been requested:

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





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9.4.  Updates to the YANG Module Names Registry

   This document requests IANA to register one YANG module in the "YANG
   Module Names" registry [RFC6020].  Following the format in [RFC6020],
   the following registration has been requested:

      name: ietf-data-object-tags
      namespace: urn:ietf:params:xml:ns:yang:ietf-data-object-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 objects 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 data object tag meta-data
   with data object 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 data object tag meta-data may define various actions to
   be taken based on the data object 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.







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11.  Acknowledgements

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

12.  Contributors

         Liang Geng
         China Mobile
         32 Xuanwumen West St, Xicheng District
         Beijing  10053

         Email: gengliang@chinamobile.com

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>.



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   [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>.

   [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

   [I-D.ietf-netconf-notification-capabilities]
              Lengyel, B., Clemm, A., and B. Claise, "YANG Modules
              describing Capabilities for Systems and Datastore Update
              Notifications", Work in Progress, Internet-Draft, draft-
              ietf-netconf-notification-capabilities-21, 15 October
              2021, <https://www.ietf.org/archive/id/draft-ietf-netconf-
              notification-capabilities-21.txt>.

   [I-D.ietf-netmod-yang-instance-file-format]
              Lengyel, B. and B. Claise, "YANG Instance Data File
              Format", Work in Progress, Internet-Draft, draft-ietf-
              netmod-yang-instance-file-format-21, 8 October 2021,
              <https://www.ietf.org/archive/id/draft-ietf-netmod-yang-
              instance-file-format-21.txt>.

   [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>.

   [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>.




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   [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>.

   [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>.

   [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>.

Appendix A.  NETCONF Example

   The following is a NETCONF example result from a query of the data
   object tags list.  For the sake of brevity only a few module and
   associated data object results are provided.
























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 <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:data-object-tags xmlns:s="urn:ietf:params:xml:ns:yang:ietf-\
          data-object-tags">
         <s:data-object>
          <s:name>/if:interfaces/if:interface</s:name>
          <s:tag>ietf:object</s:tag>
         </s:data-object>
        <s:data-object>
         <s:name>/if:interfaces/if:interface/if:last-change</\
          s:name>
         <s:tag>ietf:property</s:tag>
        </s:data-object>
         <s:data-object>
          <s:name>
           /if:interfaces/if:interface/if:statistics/if:in-errors
          </s:name>
          <s:tag>ietf:metric</s:tag>
          <s:tag>ietf:loss</s:tag>
          <s:tag>ietf:non-agg</s:tag>
         </s:data-object>
       </s:data-object-tags>
     </t:module>
     <t:module>
        <t:name>ietf-ip</t:name>
        <s:data-object-tags xmlns:s="urn:ietf:params:xml:ns:yang:ietf\
          -data-object-tags">
        <s:data-object>
          <s:name>/if:interfaces/if:interface/ip:ipv4</s:name>
          <s:tag>ietf:object</s:tag>
        </s:data-object>
        <s:data-object>
          <s:name>/if:interfaces/if:interface/ip:ipv4/ip:enable\
           </s:name>
          <s:tag>ietf:property</s:tag>
        </s:data-object>
         <s:data-object>
         <s:name>/if:interfaces/if:interface/ip:ipv4/ip:mtu</s:name>
         <s:tag>ietf:metric</s:tag>
         <s:tag>ietf:non-agg</s:tag>
        </s:data-object>
       </s:data-object-tags>
     </t:module>
   </t:module-tags>
 </ns0:data>




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                 Figure 7: Example NETCONF Query Output

Appendix B.  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.

   <CODE BEGINS> file "ietf-data-object-tags-state@2022-02-03.yang"
   module ietf-data-object-tags-state {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-data-object-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;
       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>";
     description
       "This module describes a mechanism associating self-describing
        tags with YANG data object 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 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).




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        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.";

     revision 2022-02-04 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: Self-Describing Data Object Tags";
     }

     extension opm-tag {
       argument tag;
       description
         "The argument 'tag' is of type 'tag'. This extension
          statement is used by module authors to indicate the opm tags
          that should be added automatically by the system. 'opm-tag'
          is used to classify operation and management data objects
          into the three categories, object, property, and metric.
          Data Object can contain other data objects called subobjects.
          Both object and subobjects can be modeled as data nodes. The
          Data Object tagged with object tag can be one of container,
          leaf-list and list. The Data Object tagged with the Property
          tag is a leaf node. The Data Object tagged with the Metric
          tag can be one of type container, leaf-list, list, leaf. The
          Data objects tagged with either property tag or metric tag
          are subobjects belonging to a specific root data object. Each
          Data Object may contain one single object tag, or one single
          property tag, or one single metric tag (these tags are
          mutually exclusive). As such, the origin of the value for the
          pre-defined tags should be set to 'system'.";
     }
     extension metric-type {
       argument tag;
       description
         "The argument 'tag' is of type 'tag'.The metric-type can be
          used to provide metric subobject classification
          (e.g., loss, jitter, packet loss, guage, counter, histogram,
          unknow, etc.) within the YANG module.";
     }
     extension multi-source-tag {
       argument tag;
       description
         "The argument 'tag' is of type 'tag'.The multi-source tag can
          be used to identify multi-source aggregation type(e.g.,
          aggregated, non-aggregated) related to a metric subobject.

         The 'aggregated' multi-source aggregation type allows a large



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         number of measurements on metric subobjects from different
         sources of the same type (e.g., line card, each subinterface
         of aggregated Ethernet interface) to be combined into
         aggregated statistics and reported as one metric subobject
         value. The 'non-aggregated'multi-source aggregation type
         allows measurement from each source of the same type
         (e.g., line card, each subinterface of aggregated Ethernet
         interface) to be reported separately.";
      }

     augment "/tags:module-tags/tags:module" {
       description
         "Augment the Module Tags module with data object tag
          attributes.";
       container data-object-tags {
         config false;
         status deprecated;
         description
           "Contains the list of data objects and their
            associated self describing tags.";
         list data-object {
           key "name";
           status deprecated;
           description
             "A list of data objects and their associated self
              describing tags.";
           leaf name {
             type nacm:node-instance-identifier;
             mandatory true;
             status deprecated;
             description
               "The YANG data object name.";
           }
           leaf-list tag {
             type tags:tag;
             status deprecated;
             description
               "Tags associated with the data object within the
                YANG module. See the IANA 'YANG Data Object Tag
                Prefixes' registry for reserved prefixes and the
                IANA 'IETF YANG Data Object 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.



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                2) User configured tags (i.e., tags of 'intended'
                   origin)are added.
                3) Any tag that is equal to a masked-tag is removed.";
           }
           leaf-list masked-tag {
             type tags:tag;
             status deprecated;
             description
               "The list of tags that should not be associated with the
                data object 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 object within
                YANG module, but they have no operational effect.";
           }
         }
       }
     }
   }
   <CODE ENDS>

Appendix C.  Targeted data object collection example

   The following provides targeted data object collection example which
   helps reduce amount of data to be fetched.  The subscription "id"
   values of 22 used below is just an example.  In production, the
   actual values of "id" might not be small integers.
























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    +-----------+                       +-----------+
    | Subscriber|                       | Publisher |
    +------+----+                       +-----+-----+
           |                                  |
           |                                  |
           |Telemery data Tagging Advertisement
           |  (data object name, opm-tag = metric)
           |<---------------------------------|
           |                                  |
           |    establish-subscription        |
           |--------------------------------->|
           |                                  |
           |                                  |
           |    RPC Reply: OK, id = 22        |
           |<---------------------------------|
           |                                  |
           |                                  |
           |    Notification Message (for 22) |
           | <--------------------------------|
           |                                  |
           |                                  |

   The publisher advertises telemetry data object capability to the
   subscriber to instruct the receiver to subscribe tagged data object
   (e.g., performance metric data object) using standard subscribed
   notification mechanism [RFC8639].  The corresponding telemetry data
   object capability model is created based on ietf-data-object-tags
   module defined in this document.

   The following XML example [W3C.REC-xml-20081126] illustrates the
   advertisment of the list of available target objects using YANG
   instance file format [I-D.ietf-netmod-yang-instance-file-format]:



















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   <?xml version="1.0" encoding="UTF-8"?>
   <instance-data-set xmlns=\
       "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data">
     <name>acme-router-notification-capabilities</name>
     <content-schema>
       <module>ietf-system-capabilities@2020-03-23</module>
       <module>ietf-notification-capabilities@2020-03-23</module>
       <module>ietf-data-export-capabilities@2020-03-23</module>
     </content-schema>
     <!-- revision date, contact, etc. -->
     <description>Defines the notification capabilities of an
       acme-router.The router only has running, and operational
       datastores. Every change can be reported on-change from
       running, but only config=true nodes and some config=false data
       from operational. Statistics are not reported based on timer
       based trigger and counter threshold based trigger.
     </description>
     <content-data>
       <system-capabilities \
         xmlns="urn:ietf:params:xml:ns:yang:ietf-system-capabilities" \
         xmlns:inc=\
         "urn:ietf:params:xml:ns:yang:ietf-notification-capabilities" \
         xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
         <datastore-capabilities>
           <datastore>ds:operational</datastore>
           <per-node-capabilities>
             <node-selector>\
              /if:interfaces/if:interface/if:statistics/if:in-errors\
             </node-selector>
             <sec:self-describing-capabilities>
               <sec:opm-tag>metric</sec:opm-tag>
               <sec:metric-type>loss</sec:metric-type>
             </sec:self-describing-capabilities>
           </per-node-capabilities>
         </datastore-capabilities>
       </system-capabilities>
     </content-data>
   </instance-data-set>


   With telemetry data tagging information carried in the telemetry data
   tagging Advertisement, the subscriber identifies targeted data object
   and associated data path to the datastore node and sends a standard
   establish-subscription RPC [RFC8639] to subscribe tagged data objects
   that are interests to the client application from the publisher.
   Alternatively, the subscriber can query data object tag list from
   somewhere (e.g., the network device, or offline document) using ietf-
   data-object-tags module defined in this document and fetch tagged



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   data objects and associated data path to the datastore node and sends
   a standard establish-subscription RPC [RFC8639] to subscribe tagged
   data objects that are interests to the client application from the
   publisher.

    <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>

   The publisher returns specific object type of operational state
   (e.g., in-errors statistics data) subscribed by the client.

Appendix D.  Changes between Revisions

   Editorial Note (To be removed by RFC Editor)

   v04 - v05

   *  Add user tag formating clarification;

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

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

   *  Security section enhancement for user tag managment.

   *  Change data object name into name in the module.

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




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

   v03 - v04

   *  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 objects.

   *  Update targeted data object collection example.

   v02 - v03

   *  Additional Editorial changes.

   *  Security section enhancement.

   *  Nits fixed.

   v01 - v02

   *  Clarify the relation between data object, 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 self-describing data object tag use case section into
      introduction section as a subsection;

   *  Add one glossary section;

   *  Clarify the relation between data object, object tag, property tag
      and metric tag in Self-Describing Data Object Tags Use Case
      section;

   *  Add update to RFC8407 in the front page.

Authors' Addresses





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   Qin Wu
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing
   Jiangsu, 210012
   China

   Email: bill.wu@huawei.com


   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
   Rennes 35000
   France

   Email: mohamed.boucadair@orange.com










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