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YANG Schema Item iDentifier (YANG SID)
draft-ietf-core-sid-19

Document Type Active Internet-Draft (core WG)
Authors Michel Veillette , Alexander Pelov , Ivaylo Petrov , Carsten Bormann , Michael Richardson
Last updated 2022-07-26
Replaces draft-somaraju-core-sid
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Proposed Standard
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Yang impact analysis for draft-ietf-core-sid
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draft-ietf-core-sid-19
Internet Engineering Task Force                     M. V. Veillette, Ed.
Internet-Draft                                   Trilliant Networks Inc.
Intended status: Standards Track                        A. P. Pelov, Ed.
Expires: 27 January 2023                                          Acklio
                                                          I. Petrov, Ed.
                                                 Google Switzerland GmbH
                                                              C. Bormann
                                                  Universit├Ąt Bremen TZI
                                                           M. Richardson
                                                Sandelman Software Works
                                                            26 July 2022

                 YANG Schema Item iDentifier (YANG SID)
                         draft-ietf-core-sid-19

Abstract

   YANG Schema Item iDentifiers (YANG SID) are globally unique 63-bit
   unsigned integers used to identify YANG items, as a more compact
   method to identify YANG items that can be used for efficiency and in
   constrained environments (RFC 7228).  This document defines the
   semantics, the registration, and assignment processes of YANG SIDs
   for IETF managed YANG modules.  To enable the implementation of these
   processes, this document also defines a file format used to persist
   and publish assigned YANG SIDs.

   // The present version (-19) adds in draft text about objectives,
   // parties, and roles.  This attempts to record discussions at side
   // meetings before, at, and after IETF 113.

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 27 January 2023.

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Copyright Notice

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

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology and Notation  . . . . . . . . . . . . . . . .   4
   2.  Objectives  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.1.  Technical Objectives  . . . . . . . . . . . . . . . . . .   6
     2.2.  Module evolution, versioning  . . . . . . . . . . . . . .   7
     2.3.  Solution Components and Derived Objectives  . . . . . . .   7
     2.4.  Parties and Roles . . . . . . . . . . . . . . . . . . . .   8
   3.  ".sid" file lifecycle . . . . . . . . . . . . . . . . . . . .  10
   4.  ".sid" file format  . . . . . . . . . . . . . . . . . . . . .  11
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  18
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
     6.1.  YANG Namespace Registration . . . . . . . . . . . . . . .  18
     6.2.  Register ".sid" File Format Module  . . . . . . . . . . .  19
     6.3.  Create new IANA Registry: "YANG SID Mega-Range"
           registry  . . . . . . . . . . . . . . . . . . . . . . . .  19
       6.3.1.  Structure . . . . . . . . . . . . . . . . . . . . . .  19
       6.3.2.  Allocation policy . . . . . . . . . . . . . . . . . .  20
         6.3.2.1.  First allocation  . . . . . . . . . . . . . . . .  20
         6.3.2.2.  Consecutive allocations . . . . . . . . . . . . .  21
       6.3.3.  Initial contents of the Registry  . . . . . . . . . .  21
     6.4.  Create a new IANA Registry: IETF YANG SID Range Registry
           (managed by IANA) . . . . . . . . . . . . . . . . . . . .  21
       6.4.1.  Structure . . . . . . . . . . . . . . . . . . . . . .  21
       6.4.2.  Allocation policy . . . . . . . . . . . . . . . . . .  21
       6.4.3.  Publication of the ".sid" file  . . . . . . . . . . .  23
       6.4.4.  Initial contents of the registry  . . . . . . . . . .  23
     6.5.  Create new IANA Registry: "IETF YANG SID Registry"  . . .  25
       6.5.1.  Structure . . . . . . . . . . . . . . . . . . . . . .  25
       6.5.2.  Allocation policy . . . . . . . . . . . . . . . . . .  25
       6.5.3.  Recursive Allocation of YANG SID Range at Document
               Adoption  . . . . . . . . . . . . . . . . . . . . . .  26
       6.5.4.  Initial contents of the registry  . . . . . . . . . .  27

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   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  27
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  27
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  28
   Appendix A.  ".sid" file example  . . . . . . . . . . . . . . . .  30
   Appendix B.  SID auto generation  . . . . . . . . . . . . . . . .  39
   Appendix C.  ".sid" file lifecycle  . . . . . . . . . . . . . . .  41
     C.1.  ".sid" File Creation  . . . . . . . . . . . . . . . . . .  41
     C.2.  ".sid" File Update  . . . . . . . . . . . . . . . . . . .  42
   Appendix D.  Keeping a SID File in a YANG Instance Data file  . .  43
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  44
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  44
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  44

1.  Introduction

   Some of the items defined in YANG [RFC7950] require the use of a
   unique identifier.  In both Network Configuration Protocol (NETCONF)
   [RFC6241] and RESTCONF [RFC8040], these identifiers are implemented
   using names.  To allow the implementation of data models defined in
   YANG in constrained devices [RFC7228] and constrained networks, a
   more compact method to identify YANG items is required.  This compact
   identifier, called YANG Schema Item iDentifier or YANG SID (or simply
   SID in this document and when the context is clear), is encoded using
   a 63-bit unsigned integer.  The limitation to 63-bit unsigned
   integers allows SIDs to be manipulated more easily on platforms that
   might otherwise lack 64-bit unsigned arithmetic.  The loss of a
   single bit of range is not significant given the size of the
   remaining space.

   The following items are identified using SIDs:

   *  identities

   *  data nodes (Note: including those nodes defined by the 'yang-data'
      extension.)

   *  remote procedure calls (RPCs) and associated input(s) and
      output(s)

   *  actions and associated input(s) and output(s)

   *  notifications and associated information

   *  YANG modules and features

   It is possible that some protocols use only a subset of the assigned
   SIDs, for example, for protocols equivalent to NETCONF [RFC6241] like
   [I-D.ietf-core-comi] the transportation of YANG module SIDs might be

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   unnecessary.  Other protocols might need to be able to transport this
   information, for example protocols related to discovery such as
   Constrained YANG Module Library [I-D.ietf-core-yang-library].

   SIDs are globally unique integers.  A registration system is used in
   order to guarantee their uniqueness.  SIDs are registered in blocks
   called "SID ranges".  SIDs are assigned permanently.  Items
   introduced by a new revision of a YANG module are added to the list
   of SIDs already assigned.  This is discussed in more detail in
   Section 2.

   Assignment of SIDs to YANG items is usually automated as discussed in
   Appendix B, which also discusses some cases where manual
   interventions may be appropriate.

   Section 3 provides more details about the registration process of
   YANG modules and associated SIDs.  To enable the implementation of
   this registry, Section 4 defines a standard file format used to store
   and publish SIDs.

   IETF managed YANG modules that need to allocate SIDs use the IANA
   mechanism specified in this document.  YANG modules created by other
   parties allocate SID ranges using the IANA allocation mechanisms via
   Mega-Ranges (see Section 6.3); within the Mega-Range allocation,
   those other parties are free to make up their own mechanism.

   Among other uses, YANG SIDs are particularly useful to obtain a
   compact encoding for YANG-CBOR [RFC9254].  At the time of writing, a
   tool for automated ".sid" file generation is available as part of the
   open-source project PYANG [PYANG].

1.1.  Terminology and 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.

   The following terms are defined in [RFC7950]:

   *  action

   *  feature

   *  module

   *  notification

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   *  RPC

   *  schema node

   *  schema tree

   *  submodule

   The following term is defined in [RFC8040]:

   *  yang-data extension

   This specification also makes use of the following terminology:

   *  item: A schema node, an identity, a module, or a feature defined
      using the YANG modeling language.

   *  schema-node path: A schema-node path is a string that identifies a
      schema node within the schema tree.  A path consists of the list
      of consecutive schema node identifier(s) separated by slashes
      ("/").  Schema node identifier(s) are always listed from the top-
      level schema node up to the targeted schema node and could contain
      namespace information. (e.g. "/ietf-system:system-state/clock/
      current-datetime")

   *  Namespace-qualified form - a schema node identifier is prefixed
      with the name of the module in which the schema node is defined,
      separated from the schema node identifier by the colon character
      (":").

   *  YANG Schema Item iDentifier (YANG SID or simply SID): Unsigned
      integer used to identify different YANG items.

2.  Objectives

   The overriding objective of the SID assignment and registration
   system is to ensure global interoperability of protocols that employ
   SIDs in order to communicate about data modeled in YANG.  This
   objective poses certain requirements on the stability of SIDs while
   at the same time not hindering active evolution of the YANG modules
   the SIDs are intended to support.

   Additional objectives include:

   *  enabling the developer of a YANG module to also be the originating
      entity for the SIDs pertaining to that module.

   *  making it easy for YANG developers to obtain SIDs.

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   *  enabling other developers to define SIDs for a module where the
      developer of the module is not interesting in assigning the SIDs.

   *  keeping an assignment regime that keeps short (2..4 byte) SIDs
      readily available for the applications that would benefit from
      them while at the same time employing the vast 63-bit SID space to
      facilitate permissionless actions.

   *  enabling multiple entities to provide services that support the
      assignment of SIDs.

   *  maintaining some locality in the assignment of SIDs so the
      efficiencies of the SID delta mechanism can be fully employed.

   *  enabling various software components to deal in terms of SIDs
      without having complete information about other parties in the
      communication process.

   While IANA ultimately maintains the registries that govern SIDs for
   IETF-defined modules, various support tools such as yangcatalog.org
   need to provide the support to enable SID assignment and use for
   modules still in IETF development.  Developers of open-source or
   proprietary YANG modules also need to be able to serve as such
   entities autonomously, possibly forming alliances independent of the
   IETF, while still fitting in the overall SID number space managed by
   IANA.  Obviously, this process has a number of parallels to the
   management of IP addresses, but also is very different.

2.1.  Technical Objectives

   As discussed in the introduction, SIDs are intended as globally
   unique (unsigned) integers.

   Specifically, this means that:

   *Objective 1* (MUST):  any 63-bit unsigned integer is either
      unassigned as a SID or immutably maps to EXACTLY one YANG name.
      Only the transition from unassigned to that immutable mapping is
      defined.

   This enables a recipient of a data structure employing SIDs to
   translate them into the globally meaningful YANG names that the
   existing encodings of YANG data such as YANG-XML [RFC7950] and YANG-
   JSON [RFC7951] employ today.

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   The term YANG name is not defined outside this document, and YANG has
   a complex system of names and entities that can have those names.
   Instead of defining the term technically, this set of objectives uses
   it in such a way that the overall objectives of YANG-SID can be
   achieved.

   A desirable objective is that:

   *Objective 2* (SHOULD):  any YANG name in active use has one SID
      assigned.

   This means that:

   1.  There should not be YANG names without SIDs assigned

   2.  YANG names should not have multiple SIDs assigned

   These objectives are unattainable in full, because YANG names are not
   necessarily born with a SID assignment, and because entirely
   autonomous entities might decide to assign SIDs for the same YANG
   name like ships in the night.  Note that as long as this autonomy is
   maintained, any single observer will have the impression that
   Objective 2 is attained.  Only when entities that have acted
   autonomously start communicating, a deviation is observed.

2.2.  Module evolution, versioning

   YANG modules evolve.  The technical objectives listed above are
   states in terms that are independent of this evolution.

   However, some modules are still in a very fluid state, and the
   assignment of permanent SIDs to the YANG names created in them is
   less desirable.  This is not only true for new modules, but also for
   emerging new revisions of existing stable modules.

   *Objective 3* (MUST):  the SID management system is independent from
      any module versioning.

2.3.  Solution Components and Derived Objectives

   A registration system is used in order to guarantee the uniqueness of
   SIDs.  To be able to provide some autonomy in allocation (and avoid
   information disclosure where it is not desirable), SIDs are
   registered in blocks called "SID ranges".

   SIDs are assigned permanently.

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   Items introduced by a new revision of a YANG module are added to the
   list of SIDs already assigned.

2.4.  Parties and Roles

   In the YANG development process, we can discern a number of parties
   that are concerned with a YANG module:

   module controller:
      The owner of the YANG module, i.e., the controller about its
      evolution.

   registration entity:
      The controller of the module namespace, specifically also of the
      prefixes that are in common use.  (This is not a required party.)

   module repository:
      An entity that supplies modules to module users.  This can be
      "official" (e.g., IANA for IETF modules) or unofficial (e.g.,
      yangcatalog.org).  Not all repositories are in a position to act
      as a registry, i.e., as a permanent record for the information
      they supply; these repositories need to recur to module owners as
      a stable source.

   module user:
      An entity that uses a module, after obtaining it from the module
      controller or a module repository.

   This set of parties needs to evolve to take on the additional roles
   that the SID assignment process requires:

   SID assigner:
      An entity that assigns SIDs for a module.  Objective 2 requires
      that there is only one SID assigner for each module.  SID
      assigners preferably stay the same over a module development
      process; however this specification provides SID files to ensure
      an organized handover.

   SID range registries:
      The entities that supply a SID assigner with SID ranges that they
      can use in assigning SIDs for a module.  (In this specification,
      there is a structure with mega-ranges and individual SID ranges;
      this is not relevant here.)

   SID repository:
      An entity that supplies SID assignments to SID users, usually in
      the form of a SID file.

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   SID users:
      The module user that uses the SIDs provided by a SID assigner for
      a YANG module.  SID users need to find SID assigners (or at least
      their SID assignments).

   During the introduction of SIDs, the distribution of the SID roles to
   the existing parties for a YANG module will evolve.

   The desirable end state of this evolution is:

       +====================+======================================+
       | Role               | Party                                |
       +====================+======================================+
       | SID assigner       | module developer                     |
       +--------------------+--------------------------------------+
       | SID range registry | (as discussed in this specification) |
       +--------------------+--------------------------------------+
       | SID repository     | module repository                    |
       +--------------------+--------------------------------------+
       | SID user           | module user (naturally)              |
       +--------------------+--------------------------------------+

                                  Table 1

   This grouping of roles and parties puts the module developer into a
   position where it can achieve the objectives laid out in this section
   (a "type-1", "SID-guiding" module controller).  (While a third party
   might theoretically assign additional SIDs and conflict with
   objective 2, there is very little reason to do so if SID files are
   always provided by the module developer with the module.)

   The rest of this section is concerned with the transition to this end
   state.

   For existing modules, there is no SID file.  The entity that stands
   in as the SID assigner is not specified.  This situation has the
   highest potential of a conflict with objective 2.

   Similarly, for new module development, the module owner may not have
   heard about SIDs or not be interested in assigning them (e.g.,
   because of lack of software or procedures within their organization).

   For these two cases (which we will call type-3, "SID-oblivious"
   module controller), module repositories can act as a mediator, giving
   SID users access to a SID assigner that is carefully chosen to be a
   likely choice by other module repositories as well, maximizing the
   likelihood of achieving objective 2.

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   If the module controller has heard about SIDs, but is not assigning
   them yet, it can designate a SID assigner instead.  This can lead to
   a stable, unique set of SID assignments being provided indirectly by
   a (type-2, "SID-aware") module developer.  Entities offering
   designated SID assigner services could make these available in an
   easy-to-use way, e.g., via a Web interface.

   The entity acting as a SID assigner minimally needs to record the SID
   range it uses for the SID assignment.  If the SID range registry can
   record the module name and revision, and the assignment processes
   (including the software used) are stable, the SID assigner can
   theoretically reconstruct its assignments, but this is an invitation
   for implementation bugs.

   SID assigners attending to a module in development (not yet stable)
   need to decide whether SIDs for a new revision are re-assigned from
   scratch ("clean-slate") or use existing assignments from a previous
   revision as a base, only assigning new SIDs for new names.  Once a
   module is declared stable, its SID assignments SHOULD be declared
   stable as well (the exception being that, for existing YANG modules,
   some review may be needed before this is done).

   This specification does not further discuss how mediating entities
   such as designated SID assigners or SID repositories could operate;
   instead, it supplies objectives for their operation.

3.  ".sid" file lifecycle

   YANG is a language designed to model data accessed using one of the
   compatible protocols (e.g.  NETCONF [RFC6241], RESTCONF [RFC8040] and
   CORECONF [I-D.ietf-core-comi]).  A YANG module defines hierarchies of
   data, including configuration, state data, RPCs, actions and
   notifications.

   Many YANG modules are not created in the context of constrained
   applications.  YANG modules can be implemented using NETCONF
   [RFC6241] or RESTCONF [RFC8040] without the need to assign SIDs.

   As needed, authors of YANG modules can assign SIDs to their YANG
   modules.  In order to do that, they should first obtain a SID range
   from a registry and use that range to assign or generate SIDs to
   items of their YANG module.  The assignments can then be stored in a
   ".sid" file.  For example on how this could be achieved, please refer
   to Appendix C.

   Registration of the ".sid" file associated to a YANG module is
   optional but recommended to promote interoperability between devices
   and to avoid duplicate allocation of SIDs to a single YANG module.

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   Different registries might have different requirements for the
   registration and publication of the ".sid" files.  For a diagram of
   one of the possibilities, please refer to the activity diagram on
   Figure 4 in Appendix C.

   Each time a YANG module or one of its imported module(s) or included
   sub-module(s) is updated, a new ".sid" file MAY be created if the new
   or updated items will need SIDs.  All the SIDs present in the
   previous version of the ".sid" file MUST be present in the new
   version as well.  The creation of this new version of the ".sid" file
   SHOULD be performed using an automated tool.

   If a new revision requires more SIDs than initially allocated, a new
   SID range MUST be added to the 'assignment-range' as defined in
   Section 4.  These extra SIDs are used for subsequent assignments.

   For an example of this update process, see activity diagram Figure 5
   in Appendix C.

4.  ".sid" file format

   ".sid" files are used to persist and publish SIDs assigned to the
   different YANG items of a specific YANG module.  It has the following
   structure.

   module: ietf-sid-file

     structure sid-file:
       +-- module-name            yang:yang-identifier
       +-- module-revision?       revision-identifier
       +-- sid-file-version?      sid-file-version-identifier
       +-- description?           string
       +-- dependency-revision* [module-name]
       |  +-- module-name        yang:yang-identifier
       |  +-- module-revision    revision-identifier
       +-- assignment-range* [entry-point]
       |  +-- entry-point    sid
       |  +-- size           uint64
       +-- item* [namespace identifier]
          +-- namespace     enumeration
          +-- identifier    union
          +-- sid           sid

                   Figure 1: YANG tree for ietf-sid-file

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   The following YANG module defines the structure of this file,
   encoding is performed in JSON [RFC8259] using the rules defined in
   [RFC7951].  It references ietf-yang-types defined in [RFC6991] and
   ietf-restconf defined in [RFC8040].

   RFC Ed.: please update the date of the module and Copyright if needed
   and remove this note.

   <CODE BEGINS> file "ietf-sid-file@2021-11-16.yang"
   module ietf-sid-file {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-sid-file";
     prefix sid;

     import ietf-yang-types {
       prefix yang;
       reference "RFC 6991: Common YANG Data Types.";
     }
     import ietf-yang-structure-ext {
       prefix sx;
       reference "RFC 8791: YANG Data Structure Extensions.";
     }

     organization
       "IETF Core Working Group";

     contact
       "WG Web:   <https://datatracker.ietf.org/wg/core/>

        WG List:  <mailto:core@ietf.org>

        Editor:   Michel Veillette
                  <mailto:michel.veillette@trilliant.com>

        Editor:   Andy Bierman
                  <mailto:andy@yumaworks.com>

        Editor:   Alexander Pelov
                  <mailto:a@ackl.io>

        Editor:   Ivaylo Petrov
                  <mailto:ivaylopetrov@google.com>";

     description
       "Copyright (c) 2021 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with or

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        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://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
        for full legal notices.

        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
        NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
        'MAY', and 'OPTIONAL' in this document are to be interpreted as
        described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
        they appear in all capitals, as shown here.

        This module defines the structure of the .sid files.

        Each .sid file contains the mapping between each
        string identifier defined by a YANG module and a
        corresponding numeric value called YANG SID.";

     revision 2021-11-16 {
       description
         "Initial revision.";
       reference
         "[RFC XXXX] YANG Schema Item iDentifier (YANG SID)";
     }

     typedef revision-identifier {
       type string {
         pattern '\d{4}-\d{2}-\d{2}';
       }
       description
         "Represents a date in YYYY-MM-DD format.";
     }

     typedef sid-file-version-identifier {
       type uint32;
       description
         "Represents the version of a .sid file.";
     }

     typedef sid {
       type uint64 {
         range "0..9223372036854775807";
       }
       description

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         "YANG Schema Item iDentifier";
       reference
         "[RFC XXXX] YANG Schema Item iDentifier (YANG SID)";
     }

     typedef schema-node-path {
       type string {
         pattern
           '/[a-zA-Z_][a-zA-Z0-9\-_.]*:[a-zA-Z_][a-zA-Z0-9\-_.]*' +
           '(/[a-zA-Z_][a-zA-Z0-9\-_.]*(:[a-zA-Z_][a-zA-Z0-9\-_.]*)?)*';
       }
       description
         "A schema-node path is an absolute YANG schema node identifier
         as defined by the YANG ABNF rule absolute-schema-nodeid,
         except that module names are used instead of prefixes.

         This string additionally follows the following rules:

          o  The leftmost (top-level) data node name is always in the
             namespace-qualified form.
          o  Any subsequent schema node name is in the
             namespace-qualified form if the node is defined in a module
             other than its parent node, and the simple form is used
             otherwise. No predicates are allowed.";
       reference
         "RFC 7950, The YANG 1.1 Data Modeling Language;
          Section 6.5: Schema Node Identifier;";
     }

     sx:structure sid-file {
         uses sid-file-contents;
     }

     grouping sid-file {
       description "A grouping that contains a YANG container
         representing the file structure of a .sid files.";

       container sid-file {
         description
           "A Wrapper container that together with the rc:yang-data
           extension marks the YANG data structures inside as not being
           intended to be implemented as part of a configuration
           datastore or as an operational state within the server.";
         uses sid-file-contents;
       }
     }

     grouping sid-file-contents {

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       description
         "A grouping that defines the contents of a container that
          represente the file structure of a .sid files.";

       leaf module-name {
         type yang:yang-identifier;
         mandatory true;
         description
           "Name of the YANG module associated with this .sid file.";
       }

       leaf module-revision {
         type revision-identifier;
         description
           "Revision of the YANG module associated with this .sid
           file.
           This leaf is not present if no revision statement is
           defined in the YANG module.";
       }

       leaf sid-file-version {
         type sid-file-version-identifier;
         default 0;
         description
           "Optional leaf that specifies the version number of the
           .sid file.  .sid files and the version sequence are
           specific to a given YANG module revision. This number
           starts at zero when there is a new YANG module revision and
           increases monotonically.  This number can distinguish
           updates to the .sid file which are the result of new
           processing, or the result of reported errata.";
       }

       leaf description {
         type string;
         description
           "Free-form meta information about the generated file. It
           might include .sid file generation tool and time among
           other things.";
       }

       list dependency-revision {
         key "module-name";

         description
           "Information about the used revision during the .sid file
           generation of each YANG module that the module in
           'module-name' imported.";

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         leaf module-name {
           type yang:yang-identifier;
           description
             "Name of the YANG module, dependency of 'module-name',
             for which revision information is provided.";
         }
         leaf module-revision {
           type revision-identifier;
           mandatory true;
           description
             "Revision of the YANG module, dependency of
             'module-name', for which revision information is
             provided.";
         }
       }

       list assignment-range {
         key "entry-point";
         description
           "YANG SID range(s) allocated to the YANG module identified
           by 'module-name' and 'module-revision'.

           - The YANG SID range first available value is entry-point
             and the last available value in the range is
             (entry-point + size - 1).
           - The YANG SID ranges specified by all assignment-rages
             MUST NOT overlap.";

         leaf entry-point {
           type sid;
           description
             "Lowest YANG SID available for assignment.";
         }

         leaf size {
           type uint64;
           mandatory true;
           description
             "Number of YANG SIDs available for assignment.";
         }
       }

       list item {
         key "namespace identifier";
         unique "sid";

         description
           "Each entry within this list defined the mapping between

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           a YANG item string identifier and a YANG SID. This list
           MUST include a mapping entry for each YANG item defined by
           the YANG module identified by 'module-name' and
           'module-revision'.";

         leaf namespace {
           type enumeration {
             enum module {
               value 0;
               description
                 "All module and submodule names share the same
                 global module identifier namespace.";
             }
             enum identity {
               value 1;
               description
                 "All identity names defined in a module and its
                 submodules share the same identity identifier
                 namespace.";
             }
             enum feature {
               value 2;
               description
                 "All feature names defined in a module and its
                 submodules share the same feature identifier
                 namespace.";
             }
             enum data {
               value 3;
               description
                 "The namespace for all data nodes, as defined in
                 YANG.";
             }
           }
           description
             "Namespace of the YANG item for this mapping entry.";
         }

         leaf identifier {
           type union {
             type yang:yang-identifier;
             type schema-node-path;
           }
           description
             "String identifier of the YANG item for this mapping
             entry.

             If the corresponding 'namespace' field is 'module',

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             'feature', or 'identity', then this field MUST
             contain a valid YANG identifier string.

             If the corresponding 'namespace' field is 'data',
             then this field MUST contain a valid schema node
             path.";
         }

         leaf sid {
           type sid;
           mandatory true;
           description
             "YANG SID assigned to the YANG item for this mapping
             entry.";
         }
       }
     }
   }
   <CODE ENDS>

                    Figure 2: YANG module ietf-sid-file

5.  Security Considerations

   This document defines a new type of identifier used to encode data
   that are modeled in YANG [RFC7950].  This new identifier maps
   semantic concepts to integers, and if the source of this mapping is
   not trusted, then new security risks might occur if an attacker can
   control the mapping.

   At the time of writing, it is expected that the SID files will be
   processed by a software developer, within a software development
   environment.  Developers are advised to only import SID files from
   authoritative sources.  IANA is the authoritative source for IETF
   managed YANG modules.

   Conceptually, SID files could be processed by less-constrained target
   systems such as network management systems.  Such systems need to
   take extra care to make sure that they are only processing SID files
   from authoritative sources, as authoritative as the YANG modules that
   they are using.

6.  IANA Considerations

6.1.  YANG Namespace Registration

   This document registers the following XML namespace URN in the "IETF
   XML Registry", following the format defined in [RFC3688]:

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   URI: please assign urn:ietf:params:xml:ns:yang:ietf-sid-file

   Registrant Contact: The IESG.

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

   Reference: RFC XXXX

   // RFC Ed.: please replace XXXX with RFC number and remove this note

6.2.  Register ".sid" File Format Module

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

   *  name: ietf-sid-file

   *  namespace: urn:ietf:params:xml:ns:yang:ietf-sid-file

   *  prefix: sid

   *  reference: RFC XXXX

   // RFC Ed.: please replace XXXX with RFC number and remove this note

6.3.  Create new IANA Registry: "YANG SID Mega-Range" registry

   The name of this registry is "YANG SID Mega-Range".  This registry is
   used to record the delegation of the management of a block of SIDs to
   third parties (such as SDOs or registrars).

6.3.1.  Structure

   Each entry in this registry must include:

   *  The entry point (first SID) of the registered SID block.

   *  The size of the registered SID block.  The size SHOULD be one
      million (1 000 000) SIDs, it MAY exceptionally be a multiple of
      1 000 000.

   *  The contact information of the requesting organization including:

      -  The policy of SID range allocations: Public, Private or Both.

      -  Organization name

      -  URL

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6.3.2.  Allocation policy

   The IANA policy for future additions to this registry is "Expert
   Review" [RFC8126].

   An organization requesting to manage a YANG SID Range (and thus have
   an entry in the YANG SID Mega-Range Registry), must ensure the
   following capacities:

   *  The capacity to manage and operate a YANG SID Range Registry.  A
      YANG SID Range Registry MUST provide the following information for
      all YANG SID Ranges allocated by the Registry:

      -  Entry Point of allocated YANG SID Range

      -  Size of allocated YANG SID Range

      -  Type: Public or Private

         o  Public Ranges MUST include at least a reference to the YANG
            module and ".sid" files for that YANG SID Range (e.g.,
            compare Section 6.4.3 for the IETF YANG SID registry).

         o  Private Ranges MUST be marked as "Private"

   *  A Policy of allocation, which clearly identifies if the YANG SID
      Range allocations would be Private, Public or Both.

   *  Technical capacity to ensure the sustained operation of the
      registry for a period of at least 5 years.  If Private
      Registrations are allowed, the period must be of at least 10
      years.

   If a size of the allocation beyond 1 000 000 is desired, the
   organization must demonstrate the sustainability of the technical
   approach for utilizing this size of allocation and how it does not
   negatively impact the overall usability of the SID allocation
   mechanisms; such allocations are preferably placed in the space above
   4 295 000 000 (64-bit space).

6.3.2.1.  First allocation

   For a first allocation to be provided, the requesting organization
   must demonstrate a functional registry infrastructure.

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6.3.2.2.  Consecutive allocations

   On subsequent allocation request(s), the organization must
   demonstrate the exhaustion of the prior range.  These conditions need
   to be asserted by the assigned expert(s).

   If that extra-allocation is done within 3 years from the last
   allocation, the experts need to discuss this request on the CORE
   working group mailing list and consensus needs to be obtained before
   allocating a new Mega-Range.

6.3.3.  Initial contents of the Registry

   The initial entry in this registry is allocated to IANA:

   +=============+=========+============+===================+==========+
   | Entry Point | Size    | Allocation | Organization      | URL      |
   |             |         |            | name              |          |
   +=============+=========+============+===================+==========+
   | 0           | 1000000 | Public     | IANA              | iana.org |
   +-------------+---------+------------+-------------------+----------+

                                  Table 2

6.4.  Create a new IANA Registry: IETF YANG SID Range Registry (managed
      by IANA)

6.4.1.  Structure

   Each entry in this registry must include:

   *  The SID range entry point.

   *  The SID range size.

   *  The YANG module name.

   *  Document reference.

6.4.2.  Allocation policy

   The first million SIDs assigned to IANA is sub-divided as follows:

   *  The range of 0 to 999 (size 1000) is subject to "IESG Approval" as
      defined in [RFC8126]; of these, SID value 0 has been reserved for
      implementations to internally signify the absence of a SID number
      and does not occur in interchange.

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   *  The range of 1000 to 59,999 (size 59,000) is designated for YANG
      modules defined in RFCs.

      -  The IANA policy for additions to this registry is either:

         o  "Expert Review" [RFC8126] in case the ".sid" file comes from
            a YANG module from an existing RFC, or

         o  "RFC Required" [RFC8126] otherwise.

      -  The Expert MUST verify that the YANG module for which this
         allocation is made has an RFC (existing RFC) OR is on track to
         become RFC (early allocation with a request from the WG chairs
         as defined by [BCP100]).

   *  The range of 60,000 to 99,999 (size 40,000) is reserved for
      experimental YANG modules.  This range MUST NOT be used in
      operational deployments since these SIDs are not globally unique
      which limit their interoperability.  The IANA policy for this
      range is "Experimental use" [RFC8126].

   *  The range of 100,000 to 999,999 (size 900,000) is "Reserved" as
      defined in [RFC8126].

   +=============+=========+==========================+
   | Entry Point | Size    | IANA policy              |
   +=============+=========+==========================+
   | 0           | 1,000   | IESG Approval            |
   +-------------+---------+--------------------------+
   | 1,000       | 59,000  | RFC Required             |
   +-------------+---------+--------------------------+
   | 60,000      | 40,000  | Experimental/Private use |
   +-------------+---------+--------------------------+
   | 100,000     | 900,000 | Reserved                 |
   +-------------+---------+--------------------------+

                         Table 3

   The size of the SID range allocated for a YANG module is recommended
   to be a multiple of 50 and to be at least 33% above the current
   number of YANG items.  This headroom allows assignment within the
   same range of new YANG items introduced by subsequent revisions.  The
   SID range size SHOULD NOT exceed 1000; a larger size may be requested
   by the authors if this recommendation is considered insufficient.  It
   is important to note that an additional SID range can be allocated to
   an existing YANG module if the initial range is exhausted; this then
   just leads to slightly less efficient representation.

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   In case a SID range is allocated for an existing RFC through the
   "Expert Review" policy, the Document reference field for the given
   allocation should point to the RFC that the YANG module is defined
   in.

   In case a SID range is required before publishing the RFC due to
   implementations needing stable SID values, early allocation as
   defined in [BCP100] can be employed for the "RFC Required" range
   (Section 2 of [BCP100]).

6.4.3.  Publication of the ".sid" file

   For a YANG module approved for publication as an RFC, a ".sid" file
   SHOULD be included in the Internet-Draft as a source code block.
   This ".sid" file is to be extracted by IANA/the expert reviewer and
   put into the YANG SID Registry (Section 6.5) along with the YANG
   module.  The ".sid" file MUST NOT be published as part of the RFC:
   the IANA Registry is authoritative and a link is to be inserted in
   the RFC.

6.4.4.  Initial contents of the registry

   Initial entries in this registry are as follows:

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   +=======+=====+==============+======================================+
   | Entry | Size|Module name   | Document reference                   |
   | Point |     |              |                                      |
   +=======+=====+==============+======================================+
   |     0 |    1|(Reserved: not| RFCXXXX                              |
   |       |     |a valid SID)  |                                      |
   +-------+-----+--------------+--------------------------------------+
   |  1000 |  100|ietf-coreconf | [I-D.ietf-core-comi]                 |
   +-------+-----+--------------+--------------------------------------+
   |  1100 |   50|ietf-yang-    | [RFC6991]                            |
   |       |     |types         |                                      |
   +-------+-----+--------------+--------------------------------------+
   |  1150 |   50|ietf-inet-    | [RFC6991]                            |
   |       |     |types         |                                      |
   +-------+-----+--------------+--------------------------------------+
   |  1200 |   50|iana-crypt-   | [RFC7317]                            |
   |       |     |hash          |                                      |
   +-------+-----+--------------+--------------------------------------+
   |  1250 |   50|ietf-netconf- | [RFC8341]                            |
   |       |     |acm           |                                      |
   +-------+-----+--------------+--------------------------------------+
   |  1300 |   50|ietf-sid-file | RFCXXXX                              |
   +-------+-----+--------------+--------------------------------------+
   |  1500 |  100|ietf-         | [RFC8343]                            |
   |       |     |interfaces    |                                      |
   +-------+-----+--------------+--------------------------------------+
   |  1600 |  100|ietf-ip       | [RFC8344]                            |
   +-------+-----+--------------+--------------------------------------+
   |  1700 |  100|ietf-system   | [RFC7317]                            |
   +-------+-----+--------------+--------------------------------------+
   |  1800 |  400|iana-if-type  | [RFC7224]                            |
   +-------+-----+--------------+--------------------------------------+
   |  2400 |   50|ietf-voucher  | [RFC8366]                            |
   +-------+-----+--------------+--------------------------------------+
   |  2450 |   50|ietf-         | [I-D.ietf-anima-constrained-voucher] |
   |       |     |constrained-  |                                      |
   |       |     |voucher       |                                      |
   +-------+-----+--------------+--------------------------------------+
   |  2500 |   50|ietf-         | [I-D.ietf-anima-constrained-voucher] |
   |       |     |constrained-  |                                      |
   |       |     |voucher-      |                                      |
   |       |     |request       |                                      |
   +-------+-----+--------------+--------------------------------------+

                                  Table 4

   // RFC Ed.: replace XXXX with RFC number assigned to this draft.

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   For allocation, RFC publication of the YANG module is required as per
   [RFC8126].  The YANG module must be registered in the "YANG module
   Name" registry according to the rules specified in Section 14 of
   [RFC6020].

6.5.  Create new IANA Registry: "IETF YANG SID Registry"

   The name of this registry is "IETF YANG SID Registry".  This registry
   is used to record the allocation of SIDs for individual YANG module
   items.

6.5.1.  Structure

   Each entry in this registry must include:

   *  The YANG module name.  This module name must be present in the
      "Name" column of the "YANG Module Names" registry.

   *  A link to the associated ".yang" file.  This file link must be
      present in the "File" column of the "YANG Module Names" registry.

   *  The link to the ".sid" file which defines the allocation.  The
      ".sid" file is stored by IANA.

   *  The number of actually allocated SIDs in the ".sid" file.

6.5.2.  Allocation policy

   The allocation policy is Expert review.  The Expert MUST ensure that
   the following conditions are met:

   *  The ".sid" file has a valid structure:

      -  The ".sid" file MUST be a valid JSON file following the
         structure of the module defined in RFCXXXX (RFC Ed: replace XXX
         with RFC number assigned to this draft).

   *  The ".sid" file allocates individual SIDs ONLY in the YANG SID
      Ranges for this YANG module (as allocated in the IETF YANG SID
      Range Registry):

      -  All SIDs in this ".sid" file MUST be within the ranges
         allocated to this YANG module in the "IETF YANG SID Range
         Registry".

   *  If another ".sid" file has already allocated SIDs for this YANG
      module (e.g. for older or newer versions of the YANG module), the
      YANG items are assigned the same SIDs as in the other ".sid" file.

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   *  If there is an older version of the ".sid" file, all allocated
      SIDs from that version are still present in the current version of
      the ".sid" file.

6.5.3.  Recursive Allocation of YANG SID Range at Document Adoption

   Due to the difficulty in changing SID values during IETF document
   processing, it is expected that most documents will ask for SID
   allocations using Early Allocations [BCP100].  The details of the
   Early Allocation should be included in any Working Group Adoption
   call.  Prior to Working Group Adoption, an internet draft author can
   use the experimental SID range (as per Section 6.4.2) for their SIDs
   allocations or other values that do not create ambiguity with other
   SID uses (for example they can use a range that comes from a non-IANA
   managed "YANG SID Mega-Range" registry).

   After Working Group Adoption, any modification of a ".sid" file is
   expected to be discussed on the mailing list of the appropriate
   Working Groups.  Specific attention should be paid to implementers'
   opinion after Working Group Last Call if a SID value is to change its
   meaning.  In all cases, a ".sid" file and the SIDs associated with it
   are subject to change before the publication of an internet draft as
   an RFC.

   During the early use of SIDs, many existing, previously published
   YANG modules will not have SID allocations.  For an allocation to be
   useful the included YANG modules may also need to have SID
   allocations made.

   The Expert Reviewer who performs the (Early) Allocation analysis will
   need to go through the list of included YANG modules and perform SID
   allocations for those modules as well.

   *  If the document is a published RFC, then the allocation of SIDs
      for its referenced YANG modules is permanent.  The Expert Reviewer
      provides the generated ".sid" file to IANA for registration.  This
      process may be time-consuming during a bootstrap period (there are
      over 100 YANG modules to date, none of which have SID
      allocations), but should quiet down once needed entries are
      allocated.

   *  If the document is an unprocessed Internet-Draft adopted in a WG,
      then an Early Allocation is performed for this document as well.
      Early Allocations require approval by an IESG Area Director.  An
      early allocation which requires additional allocations will list
      the other allocations in its description, and will be cross-posted
      to the any other working group mailing lists.

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   *  A YANG module which references a module in a document which has
      not yet been adopted by any working group will be unable to
      perform an Early Allocation for that other document until it is
      adopted by a working group.  As described in [BCP100], an AD
      Sponsored document acts as if it had a working group.  The
      approving AD may also exempt a document from this policy by
      agreeing to AD Sponsor the document.

   At the end of the IETF process all the dependencies of a given module
   for which SIDs are assigned, should also have SIDs assigned.  Those
   dependencies' assignments should be permanent (not Early Allocation).

   A previously SID-allocated YANG module which changes its references
   to include a YANG module for which there is no SID allocation needs
   to repeat the Early Allocation process.

   Early Allocations are made with a one-year period, after which they
   need to be renewed or will expire.

   [BCP100] also says:

   Note that if a document is submitted for review to the IESG and at
   the time of submission some early allocations are valid (not
   expired), these allocations should not be expired while the document
   is under IESG consideration or waiting in the RFC Editor's queue
   after approval by the IESG.

6.5.4.  Initial contents of the registry

   None.

7.  References

7.1.  Normative References

   [BCP100]   Cotton, M., "Early IANA Allocation of Standards Track Code
              Points", RFC 7120, BCP 100, January 2014.

              <https://www.rfc-editor.org/info/bcp100>

   [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>.

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   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <https://www.rfc-editor.org/info/rfc6991>.

   [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>.

   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <https://www.rfc-editor.org/info/rfc7951>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,
              <https://www.rfc-editor.org/info/rfc8259>.

7.2.  Informative References

   [I-D.ietf-anima-constrained-voucher]
              Richardson, M., Stok, P. V. D., Kampanakis, P., and E.
              Dijk, "Constrained Bootstrapping Remote Secure Key
              Infrastructure (BRSKI)", Work in Progress, Internet-Draft,
              draft-ietf-anima-constrained-voucher-18, 11 July 2022,
              <https://www.ietf.org/archive/id/draft-ietf-anima-
              constrained-voucher-18.txt>.

   [I-D.ietf-core-comi]
              Veillette, M., Stok, P. V. D., Pelov, A., Bierman, A., and
              I. Petrov, "CoAP Management Interface (CORECONF)", Work in
              Progress, Internet-Draft, draft-ietf-core-comi-11, 17
              January 2021, <https://www.ietf.org/archive/id/draft-ietf-
              core-comi-11.txt>.

   [I-D.ietf-core-yang-library]
              Veillette, M. and I. Petrov, "Constrained YANG Module
              Library", Work in Progress, Internet-Draft, draft-ietf-
              core-yang-library-03, 11 January 2021,
              <https://www.ietf.org/archive/id/draft-ietf-core-yang-
              library-03.txt>.

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   [PYANG]    Bjorklund, M., "An extensible YANG validator and converter
              in python", <https://github.com/mbj4668/pyang>.

   [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>.

   [RFC7224]  Bjorklund, M., "IANA Interface Type YANG Module",
              RFC 7224, DOI 10.17487/RFC7224, May 2014,
              <https://www.rfc-editor.org/info/rfc7224>.

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014,
              <https://www.rfc-editor.org/info/rfc7228>.

   [RFC7317]  Bierman, A. and M. Bjorklund, "A YANG Data Model for
              System Management", RFC 7317, DOI 10.17487/RFC7317, August
              2014, <https://www.rfc-editor.org/info/rfc7317>.

   [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>.

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

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

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

   [RFC8366]  Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
              "A Voucher Artifact for Bootstrapping Protocols",
              RFC 8366, DOI 10.17487/RFC8366, May 2018,
              <https://www.rfc-editor.org/info/rfc8366>.

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

   [RFC9254]  Veillette, M., Ed., Petrov, I., Ed., Pelov, A., Bormann,
              C., and M. Richardson, "Encoding of Data Modeled with YANG
              in the Concise Binary Object Representation (CBOR)",
              RFC 9254, DOI 10.17487/RFC9254, July 2022,
              <https://www.rfc-editor.org/info/rfc9254>.

Appendix A.  ".sid" file example

   The following ".sid" file (ietf-system@2014-08-06.sid) has been
   generated using the following yang modules:

   *  ietf-system@2014-08-06.yang (defined in [RFC7317])

   *  ietf-yang-types@2013-07-15.yang (defined in [RFC6991])

   *  ietf-inet-types@2013-07-15.yang (defined in [RFC6991])

   *  ietf-netconf-acm@2018-02-14.yang (defined in [RFC8341])

   *  iana-crypt-hash@2014-08-06.yang (defined in [RFC7317])

   For purposes of exposition, line breaks have been introduced below in
   some JSON strings that represent overly long identifiers.

   {
     "ietf-sid-file:sid-file" : {
       "module-name": "ietf-system",
       "module-revision": "2014-08-06",
       "dependency-revision": [
         {
           "module-name": "ietf-yang-types",
           "module-revision": "2013-07-15"
         },
         {
           "module-name": "ietf-inet-types",
           "module-revision": "2013-07-15"
         },
         {
           "module-name": "ietf-netconf-acm",
           "module-revision": "2018-02-14"
         },
         {
           "module-name": "iana-crypt-hash",
           "module-revision": "2014-08-06"

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         }
       ],
       "description": "Example sid file",
       "assignment-range": [
         {
           "entry-point": 1700,
           "size": 100
         }
       ],
       "item": [
         {
           "namespace": "module",
           "identifier": "ietf-system",
           "sid": 1700
         },
         {
           "namespace": "identity",
           "identifier": "authentication-method",
           "sid": 1701
         },
         {
           "namespace": "identity",
           "identifier": "local-users",
           "sid": 1702
         },
         {
           "namespace": "identity",
           "identifier": "radius",
           "sid": 1703
         },
         {
           "namespace": "identity",
           "identifier": "radius-authentication-type",
           "sid": 1704
         },
         {
           "namespace": "identity",
           "identifier": "radius-chap",
           "sid": 1705
         },
         {
           "namespace": "identity",
           "identifier": "radius-pap",
           "sid": 1706
         },
         {
           "namespace": "feature",
           "identifier": "authentication",

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           "sid": 1707
         },
         {
           "namespace": "feature",
           "identifier": "dns-udp-tcp-port",
           "sid": 1708
         },
         {
           "namespace": "feature",
           "identifier": "local-users",
           "sid": 1709
         },
         {
           "namespace": "feature",
           "identifier": "ntp",
           "sid": 1710
         },
         {
           "namespace": "feature",
           "identifier": "ntp-udp-port",
           "sid": 1711
         },
         {
           "namespace": "feature",
           "identifier": "radius",
           "sid": 1712
         },
         {
           "namespace": "feature",
           "identifier": "radius-authentication",
           "sid": 1713
         },
         {
           "namespace": "feature",
           "identifier": "timezone-name",
           "sid": 1714
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:set-current-datetime",
           "sid": 1715
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:set-current-datetime/
                         current-datetime",
           "sid": 1716
         },

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         {
           "namespace": "data",
           "identifier": "/ietf-system:system",
           "sid": 1717
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system-restart",
           "sid": 1718
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system-shutdown",
           "sid": 1719
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system-state",
           "sid": 1720
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system-state/clock",
           "sid": 1721
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system-state/clock/boot-datetime",
           "sid": 1722
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system-state/clock/
                         current-datetime",
           "sid": 1723
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system-state/platform",
           "sid": 1724
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system-state/platform/machine",
           "sid": 1725
         },
         {
           "namespace": "data",

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           "identifier": "/ietf-system:system-state/platform/os-name",
           "sid": 1726
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system-state/platform/os-release",
           "sid": 1727
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system-state/platform/os-version",
           "sid": 1728
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/authentication",
           "sid": 1729
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/authentication/user",
           "sid": 1730
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/authentication/
                         user-authentication-order",
           "sid": 1731
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/authentication/user/
                         authorized-key",
           "sid": 1732
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/authentication/user/
                         authorized-key/algorithm",
           "sid": 1733
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/authentication/user/
                         authorized-key/key-data",
           "sid": 1734
         },
         {

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           "namespace": "data",
           "identifier": "/ietf-system:system/authentication/user/
                         authorized-key/name",
           "sid": 1735
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/authentication/user/
                         name",
           "sid": 1736
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/authentication/user/
                         password",
           "sid": 1737
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/clock",
           "sid": 1738
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/clock/timezone-name",
           "sid": 1739
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/clock/timezone-utc-offset",
           "sid": 1740
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/contact",
           "sid": 1741
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/dns-resolver",
           "sid": 1742
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/dns-resolver/options",
           "sid": 1743
         },
         {

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           "namespace": "data",
           "identifier": "/ietf-system:system/dns-resolver/options/
                         attempts",
           "sid": 1744
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/dns-resolver/options/
                         timeout",
           "sid": 1745
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/dns-resolver/search",
           "sid": 1746
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/dns-resolver/server",
           "sid": 1747
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/dns-resolver/server/name",
           "sid": 1748
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/dns-resolver/server/
                         udp-and-tcp",
           "sid": 1749
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/dns-resolver/server/
                         udp-and-tcp/address",
           "sid": 1750
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/dns-resolver/server/
                         udp-and-tcp/port",
           "sid": 1751
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/hostname",
           "sid": 1752

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         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/location",
           "sid": 1753
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/ntp",
           "sid": 1754
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/ntp/enabled",
           "sid": 1755
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/ntp/server",
           "sid": 1756
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/ntp/server/
                         association-type",
           "sid": 1757
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/ntp/server/iburst",
           "sid": 1758
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/ntp/server/name",
           "sid": 1759
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/ntp/server/prefer",
           "sid": 1760
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/ntp/server/udp",
           "sid": 1761
         },
         {

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           "namespace": "data",
           "identifier": "/ietf-system:system/ntp/server/udp/address",
           "sid": 1762
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/ntp/server/udp/port",
           "sid": 1763
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/radius",
           "sid": 1764
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/radius/options",
           "sid": 1765
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/radius/options/attempts",
           "sid": 1766
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/radius/options/timeout",
           "sid": 1767
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/radius/server",
           "sid": 1768
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/radius/server/
                         authentication-type",
           "sid": 1769
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/radius/server/name",
           "sid": 1770
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/radius/server/udp",

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           "sid": 1771
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/radius/server/udp/
                         address",
           "sid": 1772
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/radius/server/udp/
                         authentication-port",
           "sid": 1773
         },
         {
           "namespace": "data",
           "identifier": "/ietf-system:system/radius/server/udp/
                         shared-secret",
           "sid": 1774
         }
       ]
     }
   }

     Figure 3: Example .sid file (ietf-system, with extra line-breaks)

   For reconstructing the actual JSON file from this figure, all line
   breaks that occur in what would be JSON strings need to be removed,
   including any following blank space (indentation) on the line after
   the line break; in each such case, a single identifier without any
   embedded blank space results.  This removal can be accomplished with
   this simple Ruby script:

   @u = %{[^"\n]*}; @q = @u + '"'
   puts ARGF.read.gsub(/^(#@q(#@q#@q)*#@u) *\n +(#@q)/, "\\1\\3")

Appendix B.  SID auto generation

   Assignment of SIDs to YANG items SHOULD be automated.  The
   recommended process to assign SIDs is as follows:

   1.  A tool extracts the different items defined for a specific YANG
       module.

   2.  The list of items is sorted in alphabetical order, 'namespace' in
       descending order, 'identifier' in ascending order.  The
       'namespace' and 'identifier' formats are described in the YANG
       module 'ietf-sid-file' defined in Section 4.

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   3.  SIDs are assigned sequentially from the entry point up to the
       size of the registered SID range.  This approach is recommended
       to minimize the serialization overhead, especially when delta
       between a reference SID and the current SID is used by protocols
       aiming to reduce message size.

   4.  If the number of items exceeds the SID range(s) allocated to a
       YANG module, an extra range is added for subsequent assignments.

   5.  The "dependency-revision" should reflect the revision numbers of
       each YANG module that the YANG module imports at the moment of
       the generation.

   When updating a YANG module that is in active use, the existing SID
   assignments are maintained.  (In contrast, when evolving an early
   draft that has not yet been adopted by a community of developers, SID
   assignments are often better done from scratch after a revision.)  If
   the name of a schema node changes, but the data remain structurally
   and semantically similar to what was previously available under an
   old name, the SID that was used for the old name MAY continue to be
   used for the new name.  If the meaning of an item changes, a new SID
   MAY be assigned to it; this is particularly useful to allow the new
   SID to identify the new structure or semantics of the item.  If the
   YANG data type changes in a new revision of a published module, such
   that the resulting CBOR encoding is changed, then implementations
   will be aided significantly if a new SID is assigned.  Note that
   these decisions are generally at the discretion of the YANG module
   author, who should decide if the benefits of a manual intervention
   are worth the deviation from automatic assignment.

   In case of an update to an existing ".sid" file, an additional step
   is needed that increments the ".sid" file version number.  If there
   was no version number in the previous version of the ".sid" file, 0
   is assumed as the version number of the old version of the ".sid"
   file and the version number is 1 for the new ".sid" file.  Apart from
   that, changes of ".sid" files can also be automated using the same
   method described above, only unassigned YANG items are processed at
   step #3.  Already existing items in the ".sid" file should not be
   given new SIDs.

   Note that ".sid" file versions are specific to a YANG module
   revision.  For each new YANG module or each new revision of an
   existing YANG module, the version number of the initial ".sid" file
   should either be 0 or should not be present.

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   Note also that RPC or action "input" and "output" data nodes MUST
   always be assigned SID even if they don't contain data nodes.  The
   reason for this requirement is that other modules can augment the
   given module and those SIDs might be necessary.

Appendix C.  ".sid" file lifecycle

   Before assigning SIDs to their YANG modules, YANG module authors must
   acquire a SID range from a "YANG SID Range Registry".  If the YANG
   module is part of an IETF draft or RFC, the SID range need to be
   acquired from the "IETF YANG SID Range Registry" as defined in
   Section 6.4.  For the other YANG modules, the authors can acquire a
   SID range from any "YANG SID Range Registry" of their choice.

   Once the SID range is acquired, owners can use it to generate ".sid"
   file/s for their YANG module/s.  It is recommended to leave some
   unallocated SIDs following the allocated range in each ".sid" file in
   order to allow better evolution of the YANG module in the future.
   Generation of ".sid" files should be performed using an automated
   tool.  Note that ".sid" files can only be generated for YANG modules
   and not for submodules.

C.1.  ".sid" File Creation

   The following activity diagram summarizes the creation of a YANG
   module and its associated ".sid" file.

        +---------------+
  o     | Creation of a |
 -+- -->| YANG module   |
 / \    +------+--------+
               |
               v
         .-------------.
        / Standardized  \     yes
        \ YANG module ? /------------+
         '-----+-------'             |
               |  no                 |
               v                     v
         .-------------.      +---------------+
   +--> / Constrained   \ yes | SID range     |
   |    \ application ? /---->| registration  |<---------+
   |     '-----+-------'      +------+--------+          |
   |           |  no                 |                   |
   |           v                     v                   |
   |    +---------------+    +---------------+           |
   +----+ YANG module   |    | SID sub-range |           |
        | update        |    | assignment    |<----------+

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        +---------------+    +-------+-------+           |
                                     |                   |
                                     v                   |
                             +---------------+    +------+------+
                             | ".sid" file   |    | Rework YANG |
                             | generation    |    |    module   |
                             +-------+-------+    +-------------+
                                     |                   ^
                                     v                   |
                                .----------.  yes        |
                               /  Work in   \ -----------+
                               \  progress  /
                                '----+-----'
                                     |  no
                                     v
                               .-------------.       .-------------.
                              /      RFC      \ no  /     Open      \ no
                              \  publication? /---> \ specification?/---+
                               '------+------'       '------+------'    |
                                 yes  |                     | yes       |
                                      |       .------------'            |
                                      |      /                          |
                                      v     v                           v
                              +---------------+               +---------------+
                              |     IANA      |               | Third party   |
                              | registration  |               | registration  |
                              +-------+-------+               +---------+-----+
                                      |                                 |
                                      +---------------------------------+
                                      v
                                    [DONE]

                       Figure 4: SID Lifecycle

C.2.  ".sid" File Update

   The following Activity diagram summarizes the update of a YANG module
   and its associated ".sid" file.

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           +---------------+
     o     | Update of the |
    -+- -->| YANG module   |
    / \    | or include(s) |
           | or import(s)  |
           +------+--------+
                  |
                  v
              .-------------.
             /  New items    \ yes
             \  created  ?   /------+
              '------+------'       |
                     |  no          v
                     |       .-------------.      +----------------+
                     |      /  SID range    \ yes | Extra sub-range|
                     |      \  exhausted ?  /---->| assignment     |
                     |       '------+------'      +-------+--------+
                     |              |  no                 |
                     |              +---------------------+
                     |              |
                     |              v
                     |      +---------------+
                     |      | ".sid" file   |
                     |      | update based  |
                     |      | on previous   |
                     |      | ".sid" file   |
                     |      +-------+-------+
                     |              |
                     |              v
                     |       .-------------.      +---------------+
                     |      /  Publicly     \ yes | YANG module   |
                     |      \  available ?  /---->| registration  |
                     |       '------+------'      +-------+-------+
                     |              | no                  |
                     +--------------+---------------------+
                                    |
                                  [DONE]

                   Figure 5: YANG and ".sid" file update

Appendix D.  Keeping a SID File in a YANG Instance Data file

   [RFC9195] defines a format for "YANG Instance Data".  This
   essentially leads to an encapsulation of the instance data within
   some metadata envelope.

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   If a SID file needs to be stored in a YANG Instance Data file, this
   can be achieved by embedding the value of the SID file as the value
   of the content-data member in the following template, and copying
   over the second-level members as indicated with the angle brackets:

   {
     "ietf-yang-instance-data:instance-data-set": {
       "name": "<module-name>@<module-revision>.sid",
       "description":  ["<description>"],
       "content-schema": {
         "module": "ietf-sid-file@2021-11-16"
       },
       "content-data": {  <replace this object>
         "ietf-sid-file:sid-file" : {
           "module-name": ...
         }
       }
     }
   }

   // RFC editor: Please replace the module date by the correct one for
   // the ietf-sid-file module.

Acknowledgments

   The authors would like to thank Andy Bierman, Michael Richardson,
   Abhinav Somaraju, Peter van der Stok, Laurent Toutain and Randy
   Turner for their help during the development of this document and
   their useful comments during the review process.  Special thanks go
   to the IESG members who supplied very useful comments during the IESG
   processing phase, in particular to Benjamin Kaduk and Rob Wilton.

Contributors

   Andy Bierman
   YumaWorks
   685 Cochran St.
   Suite #160
   Simi Valley, CA 93065
   United States of America
   Email: andy@yumaworks.com

Authors' Addresses

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   Michel Veillette (editor)
   Trilliant Networks Inc.
   610 Rue du Luxembourg
   Granby Quebec J2J 2V2
   Canada
   Phone: +14503750556
   Email: michel.veillette@trilliant.com

   Alexander Pelov (editor)
   Acklio
   1137A avenue des Champs Blancs
   35510 Cesson-Sevigne
   France
   Email: a@ackl.io

   Ivaylo Petrov (editor)
   Google Switzerland GmbH
   Brandschenkestrasse 110
   CH-8002 Zurich
   Switzerland
   Email: ivaylopetrov@google.com

   Carsten Bormann
   Universit├Ąt Bremen TZI
   Postfach 330440
   D-28359 Bremen
   Germany
   Phone: +49-421-218-63921
   Email: cabo@tzi.org

   Michael Richardson
   Sandelman Software Works
   Canada
   Email: mcr+ietf@sandelman.ca

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