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Versions: (draft-somaraju-core-sid) 00 01 02 03 04 05 06 07 08 09 10 11

Internet Engineering Task Force                        M. Veillette, Ed.
Internet-Draft                                   Trilliant Networks Inc.
Intended status: Standards Track                           A. Pelov, Ed.
Expires: July 26, 2020                                    I. Petrov, Ed.
                                                                  Acklio
                                                        January 23, 2020


                   YANG Schema Item iDentifier (SID)
                         draft-ietf-core-sid-09

Abstract

   YANG Schema Item iDentifiers (SID) are globally unique 63-bit
   unsigned integers used to identify YANG items.  This document defines
   the semantics, the registration, and assignment processes of SIDs.
   To enable the implementation of these processes, this document also
   defines a file format used to persist and publish assigned SIDs.

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 July 26, 2020.

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



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Notation  . . . . . . . . . . . . . . . . . .   3
   3.  ".sid" file lifecycle . . . . . . . . . . . . . . . . . . . .   4
   4.  ".sid" file format  . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     6.1.  Register SID File Format Module . . . . . . . . . . . . .   9
     6.2.  Create new IANA Registry: "SID Mega-Range" registry . . .   9
       6.2.1.  Structure . . . . . . . . . . . . . . . . . . . . . .   9
       6.2.2.  Allocation policy . . . . . . . . . . . . . . . . . .  10
         6.2.2.1.  First allocation  . . . . . . . . . . . . . . . .  11
         6.2.2.2.  Consecutive allocations . . . . . . . . . . . . .  11
       6.2.3.  Initial contents of the Registry  . . . . . . . . . .  11
     6.3.  Create a new IANA Registry: IETF SID Range Registry
           (managed by IANA) . . . . . . . . . . . . . . . . . . . .  11
       6.3.1.  Structure . . . . . . . . . . . . . . . . . . . . . .  11
       6.3.2.  Allocation policy . . . . . . . . . . . . . . . . . .  11
       6.3.3.  Initial contents of the registry  . . . . . . . . . .  13
     6.4.  Create new IANA Registry: "IETF SID Registry" . . . . . .  14
       6.4.1.  Structure . . . . . . . . . . . . . . . . . . . . . .  14
       6.4.2.  Allocation policy . . . . . . . . . . . . . . . . . .  14
       6.4.3.  Recursive Allocation of SID Range at Document
               Adoption  . . . . . . . . . . . . . . . . . . . . . .  15
       6.4.4.  Initial contents of the registry  . . . . . . . . . .  16
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  16
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  17
   Appendix A.  ".sid" file example  . . . . . . . . . . . . . . . .  18
   Appendix B.  SID auto generation  . . . . . . . . . . . . . . . .  27
   Appendix C.  ".sid" file lifecycle  . . . . . . . . . . . . . . .  28
     C.1.  SID File Creation . . . . . . . . . . . . . . . . . . . .  28
     C.2.  SID File Update . . . . . . . . . . . . . . . . . . . . .  29
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  30

1.  Introduction

   Some of the items defined in YANG [RFC7950] require the use of a
   unique identifier.  In both NETCONF [RFC6241] and RESTCONF [RFC8040],
   these identifiers are implemented using names.  To allow the
   implementation of data models defined in YANG in constrained devices
   and constrained networks, a more compact method to identify YANG
   items is required.  This compact identifier, called SID, is encoded



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   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 native 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:

   o  identities

   o  data nodes (Note: including those parts of a YANG template as
      defined by the 'yang-data' extension.)

   o  RPCs and associated input(s) and output(s)

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

   o  notifications and associated information

   o  YANG modules, submodules and features

   SIDs are globally unique integers, a registration system is used in
   order to guarantee their uniqueness.  SIDs are registered in blocks
   called "SID ranges".

   Assignment of SIDs to YANG items can be automated.  For more details
   how this could be achieved, please consult Appendix B.

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

   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.

2.  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]:

   o  action




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   o  feature

   o  module

   o  notification

   o  RPC

   o  schema node

   o  schema tree

   o  submodule

   The following term is defined in [RFC8040]:

   o  yang-data extension

   This specification also makes use of the following terminology:

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

   o  path: A path is a string that identifies a schema node within the
      schema tree.  A path consists of the list of 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. (e.g. "/ietf-system:system-
      state/clock/current-datetime")

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

3.  ".sid" file lifecycle

   YANG is a language designed to model data accessed using one of the
   compatible protocols (e.g.  NETCONF [RFC6241], RESCONF [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



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   items of their YANG module.  For example 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.
   Different registries might have different requirements for the
   registration and publication of the ".sid" files.  For diagram of one
   of the possibilities, please refer to the activity diagram on
   Figure 1 in Appendix C.

   Each time a YANG module or one of its imported module(s) or included
   sub-module(s) is updated, the ".sid" file MAY need to be updated.
   This update 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-ranges' as defined in
   Section 4.  These extra SIDs are used for subsequent assignments.

   For an example of this update process, see activity diagram Figure 2
   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.  The following YANG
   module defined the structure of this file, encoding is performed
   using the rules defined in [RFC7951].

   <CODE BEGINS> file "ietf-sid-file@2017-11-26.yang"
   module ietf-sid-file {
     namespace "urn:ietf:params:xml:ns:yang:ietf-sid-file";
     prefix sid;

     import ietf-yang-types {
       prefix yang;
     }

     organization
       "IETF Core Working Group";

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

        Andy Bierman
        <mailto:andy@yumaworks.com>




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        Alexander Pelov
        <mailto:a@ackl.io>";

     description
       "This module defines the structure of the .sid files.

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

     revision 2017-11-26 {
       description
         "Initial revision.";
       reference
         "[I-D.ietf-core-sid] YANG Schema Item iDentifier (SID)";
     }

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

     typedef sid {
       type uint64;
       description
         "YANG Schema Item iDentifier";
       reference
         "[I-D.ietf-core-sid] YANG Schema Item iDentifier (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
         "Identifies a schema-node path string for use in the
          SID registry. This string format follows the rules
          for an instance-identifier, as defined in RFC 7959,
          except that no predicates are allowed.

          This format is intended to support the YANG 1.1 ABNF
          for a schema node identifier, except module names
          are used instead of prefixes, as specified in RFC 7951.";



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       reference
         "RFC 7950, The YANG 1.1 Data Modeling Language;
          Section 6.5: Schema Node Identifier;
          RFC 7951, JSON Encoding of YANG Data;
          Section 6.11: The instance-identifier type";
     }

     leaf module-name {
       type yang:yang-identifier;
       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.";
     }

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

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

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

     list items {
       key "namespace identifier";
       description
         "Each entry within this list defined the mapping between
          a YANG item string identifier and a SID. This list MUST
          include a mapping entry for each YANG item defined by



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

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



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            then this field MUST contain a valid schema node
            path.";
        }

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

5.  Security Considerations

   This document defines a new type of identifier used to encode data
   models defined in YANG [RFC7950].  As such, this identifier does not
   contribute to any new security issues in addition of those identified
   for the specific protocols or contexts for which it is used.

6.  IANA Considerations

6.1.  Register SID File Format Module

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

   o  name: ietf-sid-file

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

   o  prefix: sid

   o  reference: [[THISRFC]]

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

   The name of this registry is "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).

6.2.1.  Structure

   Each entry in this registry must include:

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




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   o  The size of the registered SID block.  The size MUST be one
      million (1 000 000) SIDs.

   o  The contact information of the requesting organization including:

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

      *  Organization name

      *  URL

   The information associated to the Organization name should not be
   publicly visible in the registry, but should be available.  This
   information includes contact email and phone number and change
   controller email and phone number.

6.2.2.  Allocation policy

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

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

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

      *  Entry Point of allocated SID Range

      *  Size of allocated SID Range

      *  Type: Public or Private

         +  Public Ranges MUST include at least a reference to the YANG
            module and ".sid" files for that SID Range.

         +  Private Ranges MUST be marked as "Private"

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

   o  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.




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6.2.2.1.  First allocation

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

6.2.2.2.  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.

6.2.3.  Initial contents of the Registry

   The initial entry in this registry is allocated to IANA:

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

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

6.3.1.  Structure

   Each entry in this registry must include:

   o  The SID range entry point.

   o  The SID range size.

   o  The YANG module name.

   o  Document reference.

6.3.2.  Allocation policy

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

   o  The range of 0 to 999 (size 1000) is "Reserved" as defined in
      [RFC8126].




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   o  The range of 1000 to 59,999 (size 59,000) is reserved for YANG
      modules defined in RFCs.  The IANA policy for additions to this
      registry is "Expert Review" [RFC8126].

      *  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 [RFC7120]).

   o  The SID range allocated for a YANG module can follow in one of the
      four categories:

      *  SMALL (50 SIDs)

      *  MEDIUM (100 SIDs)

      *  LARGE (250 SIDs)

      *  CUSTOM (requested by the YANG module author, with a maximum of
         1000 SIDs).  In all cases, the size of a SID range assigned to
         a YANG module should 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.  A
         larger SID range 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.

   o  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].

   o  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   | Reserved         |
   | 1,000       | 59,000  | Expert Review    |
   | 60,000      | 40,000  | Experimental use |
   | 100,000     | 900,000 | Reserved         |
   +-------------+---------+------------------+






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6.3.3.  Initial contents of the registry

   Initial entries in this registry are as follows:

   +-----+-----+--------------------------+----------------------------+
   | Ent | Siz | Module name              | Document reference         |
   | ry  | e   |                          |                            |
   | Poi |     |                          |                            |
   | nt  |     |                          |                            |
   +-----+-----+--------------------------+----------------------------+
   | 100 | 100 | ietf-comi                | [I-D.ietf-core-comi]       |
   | 0   |     |                          |                            |
   | 110 | 50  | ietf-yang-types          | [RFC6991]                  |
   | 0   |     |                          |                            |
   | 115 | 50  | ietf-inet-types          | [RFC6991]                  |
   | 0   |     |                          |                            |
   | 120 | 50  | iana-crypt-hash          | [RFC7317]                  |
   | 0   |     |                          |                            |
   | 125 | 50  | ietf-netconf-acm         | [RFC8341]                  |
   | 0   |     |                          |                            |
   | 130 | 50  | ietf-sid-file            | RFCXXXX                    |
   | 0   |     |                          |                            |
   | 150 | 100 | ietf-interfaces          | [RFC8343]                  |
   | 0   |     |                          |                            |
   | 160 | 100 | ietf-ip                  | [RFC8344]                  |
   | 0   |     |                          |                            |
   | 170 | 100 | ietf-system              | [RFC7317]                  |
   | 0   |     |                          |                            |
   | 180 | 400 | iana-if-type             | [RFC7224]                  |
   | 0   |     |                          |                            |
   | 240 | 50  | ietf-voucher             | [RFC8366]                  |
   | 0   |     |                          |                            |
   | 245 | 50  | ietf-constrained-voucher | [I-D.ietf-anima-constraine |
   | 0   |     |                          | d-voucher]                 |
   | 250 | 50  | ietf-constrained-        | [I-D.ietf-anima-constraine |
   | 0   |     | voucher-request          | d-voucher]                 |
   +-----+-----+--------------------------+----------------------------+

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

   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].







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6.4.  Create new IANA Registry: "IETF SID Registry"

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

6.4.1.  Structure

   Each entry in this registry must include:

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

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

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

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

6.4.2.  Allocation policy

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

   o  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).

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

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

   o  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 the other ".sid"
      file.

   o  SIDs never change.






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6.4.3.  Recursive Allocation of 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 [RFC7120].  The details of the
   Early Allocation should be included in any Working Group Adoption
   call.  Prior to Working Group Adoption, an internet draft authors can
   use the experimental SID range (as per Section 6.3.2) 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 "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.

   o  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.

   o  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 it's description, and will be cross-
      posted to the any other working group mailing lists.

   o  A YANG module which references a module in an 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 [RFC7120], an AD



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      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.

   Critically, the original document should never get through the IETF
   process and then be surprised to be referencing a document whose
   progress is not certain.

   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
   are expired.  [RFC7120] indicates that at most one renewal may be
   made.  For the SID allocation a far more lenient stance is desired.

   1.  An extension of a referencing documents Early Allocation should
       update any referenced Early Allocations to expire no sooner than
       the referencing document.

   2.  The [RFC7120] mechanism allows the IESG to provide a second
       renewal, and such an event may prompt some thought about how the
       collection of documents are being processed.

   This is driven by the very generous size of the SID space and the
   often complex and deep dependencies of YANG modules.  Often a core
   module with many dependencies will undergo extensive review, delaying
   the publication of other documents.

   [RFC7120] 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.

6.4.4.  Initial contents of the registry

   None.

7.  Acknowledgments

   The authors would like to thank Andy Bierman, Carsten Bormann,
   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.




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8.  References

8.1.  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>.

   [RFC7120]  Cotton, M., "Early IANA Allocation of Standards Track Code
              Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January
              2014, <https://www.rfc-editor.org/info/rfc7120>.

   [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>.

   [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>.

8.2.  Informative References

   [I-D.ietf-anima-constrained-voucher]
              Richardson, M., Stok, P., and P. Kampanakis, "Constrained
              Voucher Artifacts for Bootstrapping Protocols", draft-
              ietf-anima-constrained-voucher-07 (work in progress),
              January 2020.

   [I-D.ietf-core-comi]
              Veillette, M., Stok, P., Pelov, A., Bierman, A., and I.
              Petrov, "CoAP Management Interface", draft-ietf-core-
              comi-08 (work in progress), September 2019.

   [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>.




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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>.

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

   [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>.

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

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

   [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>.

Appendix A.  ".sid" file example

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

   o  ietf-system@2014-08-06.yang

   o  ietf-yang-types@2013-07-15.yang




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   o  ietf-inet-types@2013-07-15.yang

   o  ietf-netconf-acm@2012-02-22.yang

   o  iana-crypt-hash@2014-04-04.yang

   {
     "assignment-ranges": [
       {
         "entry-point": 1700,
         "size": 100
       }
     ],
     "module-name": "ietf-system",
     "module-revision": "2014-08-06",
     "items": [
       {
         "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",



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         "identifier": "radius-pap",
         "sid": 1706
       },
       {
         "namespace": "feature",
         "identifier": "authentication",
         "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
       },



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       {
         "namespace": "data",
         "identifier": "/ietf-system:set-current-datetime/
                        current-datetime",
         "sid": 1716
       },
       {
         "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
       },
       {



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         "namespace": "data",
         "identifier": "/ietf-system:system-state/platform/machine",
         "sid": 1725
       },
       {
         "namespace": "data",
         "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
       },
       {



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         "namespace": "data",
         "identifier": "/ietf-system:system/authentication/user/
                        authorized-key/key-data",
         "sid": 1734
       },
       {
         "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
       },



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       {
         "namespace": "data",
         "identifier": "/ietf-system:system/dns-resolver/options",
         "sid": 1743
       },
       {
         "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",



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         "sid": 1751
       },
       {
         "namespace": "data",
         "identifier": "/ietf-system:system/hostname",
         "sid": 1752
       },
       {
         "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
       },



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       {
         "namespace": "data",
         "identifier": "/ietf-system:system/ntp/server/udp",
         "sid": 1761
       },
       {
         "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",



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         "identifier": "/ietf-system:system/radius/server/name",
         "sid": 1770
       },
       {
         "namespace": "data",
         "identifier": "/ietf-system:system/radius/server/udp",
         "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
       }
     ]
   }

Appendix B.  SID auto generation

   Assignment of SIDs to YANG items can 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.

   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.




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

   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.

Appendix C.  ".sid" file lifecycle

   Before assigning SIDs to their YANG modules, YANG module authors must
   acquire a SID range from a "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 SID Range Registry" as defined in Section 6.3.  For
   the other YANG modules, the authors can acquire a SID range from any
   "SID Range Registry" of their choice.

   Once the SID range is acquired, the owner can use it to generate
   ".sid" file/s for his 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                   |
   |   +---------------+     +---------------+           |



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   +---| YANG module   |     | SID sub-range |           |
       | update        |     | assignment    |<----------+
       +---------------+     +---------------+           |
                                     |                   |
                                     V                   |
                             +---------------+    +-------------+
                             | .sid file     |    | Rework YANG |
                             | generation    |    |    model    |
                             +---------------+    +-------------+
                                     |                   ^
                                     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 1: 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 2: YANG and SID file update

Authors' Addresses









Veillette, et al.         Expires July 26, 2020                [Page 30]


Internet-Draft      YANG Schema Item iDentifier (SID)       January 2020


   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
   Cesson-Sevigne, Bretagne  35510
   France

   Email: a@ackl.io


   Ivaylo Petrov (editor)
   Acklio
   1137A avenue des Champs Blancs
   Cesson-Sevigne, Bretagne  35510
   France

   Email: ivaylo@ackl.io

























Veillette, et al.         Expires July 26, 2020                [Page 31]


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