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NETMOD Working Group                                               Q. Wu
Internet-Draft                                                    Huawei
Intended status: Standards Track                               B. Claise
Expires: March 26, 2021                                            Cisco
                                                                 L. Geng
                                                                   Z. Du
                                                            China Mobile
                                                            M. Boucadair
                                                                  Orange
                                                      September 22, 2020


                    Self Describing Data Object Tags
                   draft-tao-netmod-yang-node-tags-06

Abstract

   This document defines a method to tag data objects associated with
   operation and management data in YANG Modules.  This YANG data object
   tagging method can be used to classify data objects from different
   YANG modules and identify characteristics data.  It also can provide
   input, instruction, indication to selection filter and filter queries
   of operational state on a server during a "pub/sub" service for YANG
   datastore updates.  When the state of all subscriptions of a
   particular Subscriber to be fetched is huge, the amount of data to be
   streamed out to the destination can be greatly reduced and only
   targeted to the characteristics data.  These data object tags may be
   registered as well as assigned during the module definition; assigned
   by implementations; or dynamically defined and set by users.

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 March 26, 2021.





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Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Self Describing Data Object Tags Use Case . . . . . . . .   4
       1.1.1.  Massive Data Object Collection  . . . . . . . . . . .   4
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   6
   2.  Data Object Tag Values  . . . . . . . . . . . . . . . . . . .   6
     2.1.  IETF Tags Prefix  . . . . . . . . . . . . . . . . . . . .   7
     2.2.  Vendor Tags Prefix  . . . . . . . . . . . . . . . . . . .   7
     2.3.  User Tags Prefix  . . . . . . . . . . . . . . . . . . . .   7
     2.4.  Reserved Tags Prefix  . . . . . . . . . . . . . . . . . .   7
   3.  Data Object Tag Management  . . . . . . . . . . . . . . . . .   7
     3.1.  Module Design Tagging . . . . . . . . . . . . . . . . . .   8
     3.2.  Implementation Tagging  . . . . . . . . . . . . . . . . .   8
     3.3.  User Tagging  . . . . . . . . . . . . . . . . . . . . . .   9
   4.  Data Object Tags Module Structure . . . . . . . . . . . . . .   9
     4.1.  Data Object Tags Module Tree  . . . . . . . . . . . . . .   9
   5.  YANG Module . . . . . . . . . . . . . . . . . . . . . . . . .   9
   6.  Guidelines to Model Writers . . . . . . . . . . . . . . . . .  12
     6.1.  Define Standard Tags  . . . . . . . . . . . . . . . . . .  12
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
     7.1.  YANG Data Object Tag Prefixes Registry  . . . . . . . . .  13
     7.2.  IETF YANG Data Object Tags Registry . . . . . . . . . . .  14
     7.3.  Updates to the IETF XML Registry  . . . . . . . . . . . .  16
     7.4.  Updates to the YANG Module Names Registry . . . . . . . .  16
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  17
     10.2.  Informative References . . . . . . . . . . . . . . . . .  17
   Appendix A.  NETCONF Example  . . . . . . . . . . . . . . . . . .  18
   Appendix B.  Non-NMDA State Module  . . . . . . . . . . . . . . .  19
   Appendix C.  Targeted data object collection example  . . . . . .  22



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   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  25

1.  Introduction

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

   At the time of writing this document (2020), there are many data
   models that have been specified or are being specified by various
   different SDOs and Open Souce community.  They 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, security management
   categories information at different locations in various different
   ways, lack consistent classification criteria and representation for
   a specific service, feature or data source.

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

   o  Provide dictionary meaning for specific targeted data objects;

   o  Indicate relationship between data objects within the same YANG
      module or from different YANG modules;

   o  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 client to
   classify data objects from different YANG modules and identify
   characteristics data.  In addition, it can provide input,
   instruction, indication to selection filter and filter queries of
   configuration or operational state on a server based on these data
   object tags, .e.g., return specific object type of operational state
   related to system-management.  NETCONF clients can discover data
   objects with self describing data object tags supported by a NETCONF
   server via <get-schema> operation.  The self describing data object
   tag capability can also be advertised via Capability Notification
   Model [I-D.netconf-notification-capabilities] by the NETCONF server
   or some place where offline document are kept.  These data object
   tags may be registered as well as 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 module
   tag model 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 an extension statement 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 6 provides guidelines for authors of YANG data models.

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

1.1.  Self Describing Data Object Tags Use Case

1.1.1.  Massive Data Object Collection

   Among data object tags, the opm (object, property subobject, metric
   subobject) tags can be used to tackle massive data objects collection
   and only capture YANG data objects associated with performance
   metrics data modelled with YANG (See Figure 1).

























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   /-----\                                 /-----\
  /Property\                             /Property\
  |Subobject+------+             +-------+Subobject|
  \   A     /      |             |        \   B   /
    +- ---+     +--V-------------V-+        -----      +---------------+
                | YANG Data Node   |                   | YANG Data Node|
                | /Data Object 1   |-------------------| /Data Object 3|
     /---\      +--^-------------^-+        /---\      +-------^-------+
    Metric\        |     |       |         Metric              |
   |Subobject------+     |       +--------|Subobject        /--+-\
    \  C  /              |                 \  D  /         Property
     \-+-/               |                  \-+-/         |Subobject
                         |        +------+    |            \   G  /
                         |        |Metric+----+             \----/
                         |        |Group |----+
      /----\             |        +------+    |
     Property            |                    |
    |Subobject           |                    |
     \   E  /            |                    |
      \--+-/             |                 /----\
         |   +-------------------+        /Metric\
         |   |   YANG Data Node  <-------|Subobject
         +--->  /Data Object 2   |        \  F   /
             +-------------------+         \----/

        Figure 1: The Relation between Object, Property and Metric

   In Figure 1, object can contain other objects called subobjects.
   Property and metric objects are both subobjects belonging to specific
   object.  Both object and subobjects can be modeled as YANG data nodes
   [RFC7950].  Object can be one of container, leaf-list and list.
   Property subobject is a leaf node.  Metric subobject can be one of
   container, leaf-list, list, leaf node.  Object contains zero or many
   property subobjects, zero or many metric subobjects.

   The use of opm tags would be 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
   property data in the single view of the truth (see Figure 2).  In
   Figure 2, tunnel-svc data object is a container node in the tunnel-pm
   module and can be seen as the root object for property subobjects
   (e.g., tunnel-svc/create-time) and metric subobjects (e.g.,tunnel-
   svc/avg-latency).  Name, create-time, modified-time are property
   subobjects under tunnel-svc container.  Avg-latency,packet loss are
   metric subobjects under tunnel-svc container node.  In addition, not
   all metric subobjects need to be tagged, e.g., only specific category
   (e.g., loss related) metric subobjects need to be tagged with metric-
   group tag which can further reduce amount data to be fetched.



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 +------------------------+--------------------------------------------+
 |      Data              |  Object    Property     Metric      Module |
 |      Object            |   Tag      Subobject    Subobject    Name  |
 |                        |              Tag         Tag               |
 +------------------------+--------------------------------------------+
 |                        |  ietf:                                     |
 |tunnel-svc              |  object                           tunnel-pm|
 |                        |            ietf:                           |
 |tunnel-svc/name         |            property               tunnel-pm|
 |                        |            ietf:                           |
 |tunnel-svc/create-time  |            property               tunnel-pm|
 |                        |            ietf:                           |
 |tunnel-svc/modified-time|            property               tunnel-pm|
 |                        |                                            |
 |tunnel-svc/avg-latency  |                        ietf:      tunnel-pm|
 |                        |                        metric              |
 |tunnel-svc/packet-loss  |                        ietf:      tunnel-pm|
 |                        |                        metric              |
 |tunnel-svc/min-latency  |                        ietf:      tunnel-pm|
 |                        |                        metric              |
 |tunnel-svc/ max-latency |                        ietf:      tunnel-pm|
 |                        |                        metric              |
 +------------------------+--------------------------------------------+

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

   If data objects in these 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

1.2.  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.

2.  Data Object Tag Values

   All data object tags SHOULD begin with a prefix indicating who owns
   their definition.  An IANA registry (Section 7.1) is used to support
   registering data object tag prefixes.  Currently 3 prefixes are
   defined.





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   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 and tabs.
   Therefore, designers, implementers, and users are free to add or not
   add any structure they may require to their own tag values.

2.1.  IETF Tags Prefix

   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
   later in this document (Section 7.2).

2.2.  Vendor Tags Prefix

   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 include extra
   identification in the tag to avoid collisions such as using the
   enterprise or organization name following the "vendor:" prefix (e.g.,
   vendor:vendor-defined-classifier).

2.3.  User Tags Prefix

   A user tag is any tag that has the prefix "user:".  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 prefix collisions.

2.4.  Reserved Tags Prefix

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

3.  Data Object Tag Management

   Tags can become associated with a data object within YANG module in a
   number of ways.  Tags may be defined and associated at the module
   design time, at implementation time without the need of live server,
   or via user administrative control . As the main consumer 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.








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3.1.  Module Design Tagging

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

   opm-tag extension statement:  Classify management and operation data
      into object, property subobject and metric subobject three
      categories.  Object can contain other objects called subobjects.
      Property and metric objects are both subobjects belonging to
      specific object.  Both object and subobjects can be modeled as
      data nodes [RFC7950].  Object can be one of container, leaf-list
      and list.  Property subobject is a leaf node.  Metric subobject
      can be one of container, leaf-list, list, leaf.  Object contains
      zero or many property subobjects, zero or many metric subobjects.
      See opm-tag example in Figure 2 and Figure 3.

   metric-group extension statement:  Provide meric subobjects
      classification (e.g., loss, jitter, delay) within the YANG module.

   multi-source-tag extension statement:  Identify multi-source
      aggregation type (e.g., aggregated, non-aggregated) related to
      metric subobject. '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) being combined into
      aggregated statistics and report as one metric subobject.  '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) be reported separately.

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

   If the data node is defined in an IETF standards track document, the
   data object tags MUST be IETF Tags (2.1).  Thus, new data object can
   drive the addition of new IETF tags to the IANA registry defined in
   Section 7, and the IANA registry can serve as a check against
   duplication.

3.2.  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 specific tags.





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3.3.  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.

4.  Data Object Tags Module Structure

4.1.  Data Object Tags Module Tree

   The tree associated with the "ietf-data-object-tags" module follows.
   The meaning of the symbols can be found in [RFC8340].

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

5.  YANG Module

<CODE BEGINS> file "ietf-data-object-tags@2019-05-03.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;
  }
  import ietf-module-tags {
    prefix tags;
  }

  organization
    "IETF NetMod Working Group (NetMod)";
  contact
    "WG Web:  <https://tools.ietf.org/wg/netmod/>
     WG List: <mailto:netmod@ietf.org>
     Editor:  Qin Wu <mailto:bill.wu@huawei.com>
     Editor:  Benoit Claise <mailto:bclaise@cisco.com>
     Editor:  Liang Geng <mailto:gengliang@chinamobile.com>
     Editor:  Zongpeng Du <mailto:duzongpeng@chinamobile.com>



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     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) 2020 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://tools.ietf.org/html/rfcXXXX); see the RFC itself for
     full legal notices.";

  revision 2019-05-03 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: YANG 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 into object, property subobject, and metric
       subobject three categories. Object can contain other objects called subobjects.
       Property and metric objects are both subobjects belonging to specific object.
       Both object and subobjects can be modeled as data nodes. Object can be one of
       container, leaf-list and list. Property subobject is a leaf node. Metric subobject
       can be one of container, leaf-list, list, leaf. Object contains zero or many
       property subobjects, zero or many metric subobjects. As such the origin of the
       value for the pre-defined tags should be set to 'system'[RFC8342].";
  }

  extension metric-group {
    argument tag;
    description
      "The argument 'tag' is of type 'tag'.The metric-group can be
       used to provide metric subobject classification



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       (e.g., loss, jitter, packet loss) 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 metric subobject.

      '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)
      being combined into aggregated statistics and report as one metric subobject
      value. '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) 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 "object-name";
        description
          "A list of data objects and their associated data object tags";
        leaf object-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 [RFC8342] 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)



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             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) tags from the
             operational state datastore [RFC8342] 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>

6.  Guidelines to Model Writers

   This section updates [RFC8407].

6.1.  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).






















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    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";
               }
             }
           container Y {
             leaf bar {
             ntags:opm-tag "ietf:metric";
             }
         }
       }
     // ...
    }

                     Figure 3: 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 below, see
   Section Section 7.2.

7.  IANA Considerations

7.1.  YANG Data Object Tag Prefixes Registry

   IANA is asked to create a new registry "YANG Data Object Tag
   Prefixes" grouped under a new "Protocol" category named "YANG Data
   Object Tag Prefixes".

   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.

   The initial values for this registry are as follows.




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

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

7.2.  IETF YANG Data Object Tags Registry

   IANA is asked to create 3 new registries "IETF OPM Tags","IETF Metric
   Group Tags","IETF Multiple Source Tags" grouped under a new
   "Protocol" category.  These 3 registries should be included below
   "YANG Data Object Tag Prefixes" when listed on the same page.

   3 registries 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 registries is IETF Review
   [RFC8126].

   The initial values for these three registries are as follows.




















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   +----------------------------+--------------------------+-----------+
   | OPM Tag                    | Description              | Reference |
   +----------------------------+--------------------------+-----------+
   |                            |                          |           |
   | ietf:object                |Represent specific object | [This     |
   |                            |type(e.g., interfaces).   | document] |
   |                            |                          |           |
   | ietf:property              |Represent  a property     | [This     |
   |                            |subobject (e.g.,ifindex)  | document] |
   |                            |assoiciated with specific |           |
   |                            |object (e.g.,interfaces). |           |
   |                            |                          |           |
   | ietf:metric                |Represent metric subobject| [This     |
   |                            |(e.g., ifstatistics)      | document] |
   |                            |associated with specific  |           |
   |                            | object(e.g.,interfaces)  |           |
   +----------------------------+--------------------------+-----------+
   +----------------------------+--------------------------+-----------+
   | Metric Group Tag           | Description              | Reference |
   +----------------------------+--------------------------+-----------+
   | ietf:delay                 |Represent the metric group| [This     |
   |                            |which metric subobjects   | document] |
   |                            |belong to (i.e., delay)   |           |
   |                            |                          |           |
   | ietf:jitter                |Represent the metric group| [This     |
   |                            |which metric subobjects   |document]  |
   |                            |belong to (i.e., jitter)  |           |
   |                            |                          |           |
   | ietf:loss                  |Represent the metric group| [This     |
   |                            |which metric subobjects   | document] |
   |                            |belong to (i.e.,loss)     |           |
   +----------------------------+--------------------------+-----------+
   +----------------------------+--------------------------+-----------+
   | Multiple Source Tag        | Description              | Reference |
   +----------------------------+--------------------------+-----------+
   |ietf:non-agg                |Relate to multiple source | [This     |
   |                            |aggregation type(i.e.,    | document] |
   |                            |aggregated statistics)    |           |
   |                            |                          |           |
   |ietf:agg                    |Relate to multiple source | [This     |
   |                            |aggregation type(i.e., non| document] |
   |                            |aggregated statistics)    |           |
   +----------------------------+--------------------------+-----------+

   Each YANG data object can have one opm tag, zero or one metric-group
   tag, zero or one multi-source tag.





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7.3.  Updates to the IETF XML Registry

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

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

7.4.  Updates to the YANG Module Names Registry

   This document registers one YANG module in the "YANG Module Names"
   registry [RFC6020].  Following the format in [RFC6020], the following
   registration has been made:

     name:
        ietf-data-object-tags
     namespace:
        urn:ietf:params:xml:ns:yang:ietf-data-object-tags
     prefix:
        ntags
     reference:
        RFC XXXX (RFC Ed.: replace XXX with actual RFC number and remove
        this note.)

8.  Security Considerations

   The YANG module defined in this memo is designed to be accessed via
   the NETCONF protocol [RFC6241].  The lowest NETCONF layer is the
   secure transport layer and the mandatory-to-implement secure
   transport is SSH [RFC6242].

   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.




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9.  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, Peng Liu, YingZhen Qu, Boyuan Yan.

10.  References

10.1.  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>.

   [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>.

   [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>.

   [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>.

   [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>.

10.2.  Informative References

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






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

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

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

   [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>.

   [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 fictional 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 imagined.



















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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:object-name>/if:interfaces/if:interface</s:object-name>
         <s:tag>ietf:object</s:tag>
        </s:data-object>
       <s:data-object>
        <s:object-name>/if:interfaces/if:interface/if:last-change</s:object-name>
        <s:tag>ietf:property</s:tag>
       </s:data-object>
        <s:data-object>
         <s:object-name>
          /if:interfaces/if:interface/if:statistics/if:in-errors
         </s:object-name>
         <s:tag>ietf:metric</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:object-name>/if:interfaces/if:interface/ip:ipv4</s:object-name>
         <s:tag>ietf:object</s:tag>
       </s:data-object>
       <s:data-object>
         <s:object-name>/if:interfaces/if:interface/ip:ipv4/ip:enable</s:object-name>
         <s:tag>ietf:property</s:tag>
       </s:data-object>
        <s:data-object>
        <s:object-name>/if:interfaces/if:interface/ip:ipv4/ip:mtu</s:object-name>
        <s:tag>ietf:metric</s:tag>
       </s:data-object>
      </s:data-object-tags>
    </t:module>
  </t:module-tags>
</ns0:data>

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@2019-05-03.yang"
module ietf-data-object-tags-state {



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  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;
  }
  import ietf-module-tags {
    prefix tags;
  }
  organization
    "IETF NetMod Working Group (NetMod)";
  contact
    "WG Web:  <https://tools.ietf.org/wg/netmod/>
     WG List: <mailto:netmod@ietf.org>
     Editor:  Qin Wu <mailto:bill.wu@huawei.com>
     Editor:  Benoit Claise <mailto:bclaise@cisco.com>
     Editor:  Liang Geng <mailto:gengliang@chinamobile.com>
     Editor:  Zongpeng Du <mailto:duzongpeng@chinamobile.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) 2020 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://tools.ietf.org/html/rfcXXXX); see the RFC itself for
     full legal notices.";

  revision 2019-05-03 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: YANG Data Object Tags";
  }

  extension opm-tag {
    argument tag;
    description



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      "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 into object, property subobject, and metric
       subobject three categories. Object can contain other objects called subobjects.
       Property and metric objects are both subobjects belonging to specific object.
       Both object and subobjects can be modeled as data nodes. Object can be one of
       container, leaf-list and list. Property subobject is a leaf node. Metric subobject
       can be one of container, leaf-list, list, leaf. Object contains zero or many
       property subobjects, zero or many metric subobjects. As such the origin of the value
       for the pre-defined tags should be set to 'system'[RFC8342].";
  }
  extension metric-group {
    argument tag;
    description
      "The argument 'tag' is of type 'tag'.The metric-group can be
       used to provide metric subobject classification
       (e.g., loss, jitter, packet loss)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 metric subobject.

      '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)
      being combined into aggregated statistics and report as one metric subobject
      value. '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) 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 "object-name";
        status deprecated;
        description
          "A list of data objects and their associated self describing tags";



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        leaf object-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 [RFC8342] 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;
          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 [RFC8342] 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 subsections 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 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-group>loss</sec:metric-group>
          </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.







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 <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-notifications"
       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.

Authors' Addresses

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

   Email: bill.wu@huawei.com


   Benoit Claise
   Cisco
   De Kleetlaan 6a b1
   Diegem  1831
   Belgium

   Email: bclaise@cisco.com


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

   Email: gengliang@chinamobile.com



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   Zongpeng Du
   China Mobile
   32 Xuanwumen West St, Xicheng District
   Beijing  10053

   Email: duzongpeng@chinamobile.com


   Mohamed Boucadair
   Orange
   Rennes 35000
   France

   Email: mohamed.boucadair@orange.com





































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