Internet Engineering Task Force M.V. Veillette, Ed. Internet-Draft Trilliant Networks Inc. Intended status: Standards Track A.P. Pelov, Ed. Expires: 22 May 2022 Acklio I. Petrov, Ed. Google Switzerland GmbH C. Bormann Universität Bremen TZI M. Richardson Sandelman Software Works 18 November 2021 YANG Schema Item iDentifier (YANG SID) draft-ietf-core-sid-18 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. 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 22 May 2022. Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. Veillette, et al. Expires 22 May 2022 [Page 1] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology and Notation . . . . . . . . . . . . . . . . . . 4 3. ".sid" file lifecycle . . . . . . . . . . . . . . . . . . . . 5 4. ".sid" file format . . . . . . . . . . . . . . . . . . . . . 6 5. Content-Types . . . . . . . . . . . . . . . . . . . . . . . . 13 6. Security Considerations . . . . . . . . . . . . . . . . . . . 13 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 7.1. YANG Namespace Registration . . . . . . . . . . . . . . . 14 7.2. Register ".sid" File Format Module . . . . . . . . . . . 14 7.3. Create new IANA Registry: "YANG SID Mega-Range" registry . . . . . . . . . . . . . . . . . . . . . . . . 15 7.3.1. Structure . . . . . . . . . . . . . . . . . . . . . . 15 7.3.2. Allocation policy . . . . . . . . . . . . . . . . . . 15 7.3.2.1. First allocation . . . . . . . . . . . . . . . . 16 7.3.2.2. Consecutive allocations . . . . . . . . . . . . . 16 7.3.3. Initial contents of the Registry . . . . . . . . . . 16 7.4. Create a new IANA Registry: IETF YANG SID Range Registry (managed by IANA) . . . . . . . . . . . . . . . . . . . . 17 7.4.1. Structure . . . . . . . . . . . . . . . . . . . . . . 17 7.4.2. Allocation policy . . . . . . . . . . . . . . . . . . 17 7.4.3. Publication of the ".sid" file . . . . . . . . . . . 18 7.4.4. Initial contents of the registry . . . . . . . . . . 19 7.5. Create new IANA Registry: "IETF YANG SID Registry" . . . 21 7.5.1. Structure . . . . . . . . . . . . . . . . . . . . . . 21 7.5.2. Allocation policy . . . . . . . . . . . . . . . . . . 21 7.5.3. Recursive Allocation of YANG SID Range at Document Adoption . . . . . . . . . . . . . . . . . . . . . . 22 7.5.4. Initial contents of the registry . . . . . . . . . . 23 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 8.1. Normative References . . . . . . . . . . . . . . . . . . 23 8.2. Informative References . . . . . . . . . . . . . . . . . 24 Appendix A. ".sid" file example . . . . . . . . . . . . . . . . 26 Appendix B. SID auto generation . . . . . . . . . . . . . . . . 36 Appendix C. ".sid" file lifecycle . . . . . . . . . . . . . . . 37 C.1. ".sid" File Creation . . . . . . . . . . . . . . . . . . 37 C.2. ".sid" File Update . . . . . . . . . . . . . . . . . . . 38 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 39 Veillette, et al. Expires 22 May 2022 [Page 2] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40 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 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". Veillette, et al. Expires 22 May 2022 [Page 3] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 SIDs are assigned permanently. Items introduced by a new revision of a YANG module are added to the list of SIDs already assigned. Assignment of SIDs to YANG items are 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 7.3); within the Mega-Range allocation, those other parties are free to make up their own mechanism. At the time of writing, a tool for automated ".sid" file generation is available as part of the open-source project PYANG [PYANG]. 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]: * action * feature * module * notification * RPC * schema node * schema tree * submodule The following term is defined in [RFC8040]: Veillette, et al. Expires 22 May 2022 [Page 4] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 * 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. 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. Veillette, et al. Expires 22 May 2022 [Page 5] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 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 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 Veillette, et al. Expires 22 May 2022 [Page 6] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 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. 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: WG List: Editor: Michel Veillette Editor: Andy Bierman Editor: Alexander Pelov Editor: Ivaylo Petrov "; 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 Veillette, et al. Expires 22 May 2022 [Page 7] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 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 Veillette, et al. Expires 22 May 2022 [Page 8] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 "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 { Veillette, et al. Expires 22 May 2022 [Page 9] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 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."; Veillette, et al. Expires 22 May 2022 [Page 10] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 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 Veillette, et al. Expires 22 May 2022 [Page 11] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 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', Veillette, et al. Expires 22 May 2022 [Page 12] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 '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."; } } } } Figure 2: YANG module ietf-sid-file 5. Content-Types The following Content-Type has been defined in [I-D.ietf-core-yang-cbor]: application/yang-data+cbor; id=sid: This Content-Type represents a CBOR YANG document containing one or multiple data node values. Each data node is identified by its associated SID. FORMAT: CBOR map of SID, instance-value The message payload of Content-Type 'application/yang-data+cbor' is encoded using a CBOR map. Each entry within the CBOR map contains the data node identifier (i.e. SID) and the associated instance-value. Instance-values are encoded using the rules defined in Section 4 of [I-D.ietf-core-yang-cbor]. 6. 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. Veillette, et al. Expires 22 May 2022 [Page 13] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 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. 7. IANA Considerations 7.1. YANG Namespace Registration This document registers the following XML namespace URN in the "IETF XML Registry", following the format defined in [RFC3688]: 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 7.2. 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 Veillette, et al. Expires 22 May 2022 [Page 14] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 7.3. 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). 7.3.1. 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 7.3.2. 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 7.4.3 for the IETF YANG SID registry). o Private Ranges MUST be marked as "Private" Veillette, et al. Expires 22 May 2022 [Page 15] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 * 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). 7.3.2.1. First allocation For a first allocation to be provided, the requesting organization must demonstrate a functional registry infrastructure. 7.3.2.2. 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. 7.3.3. 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 1 Veillette, et al. Expires 22 May 2022 [Page 16] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 7.4. Create a new IANA Registry: IETF YANG SID Range Registry (managed by IANA) 7.4.1. Structure Each entry in this registry must include: * The SID range entry point. * The SID range size. * The YANG module name. * Document reference. 7.4.2. 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. * 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]. Veillette, et al. Expires 22 May 2022 [Page 17] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 +=============+=========+==========================+ | 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 2 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. 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. As specified in Section 4.6 of [RFC8126], RFCs and by extension documents that are expected to become an RFC fulfill the requirement for "Specification Required" stated in Section 2 of [BCP100], which allows for the early allocation process to be employed. 7.4.3. 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 7.5) 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. Veillette, et al. Expires 22 May 2022 [Page 18] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 7.4.4. Initial contents of the registry Initial entries in this registry are as follows: Veillette, et al. Expires 22 May 2022 [Page 19] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 +=======+=====+==============+======================================+ | 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 3 // RFC Ed.: replace XXXX with RFC number assigned to this draft. Veillette, et al. Expires 22 May 2022 [Page 20] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 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]. 7.5. 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. 7.5.1. 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. 7.5.2. 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. Veillette, et al. Expires 22 May 2022 [Page 21] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 * 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. 7.5.3. 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 7.4.2) 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. Veillette, et al. Expires 22 May 2022 [Page 22] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 * 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 are expired. [BCP100] 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 [BCP100] 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. [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. 7.5.4. Initial contents of the registry None. 8. References 8.1. Normative References Veillette, et al. Expires 22 May 2022 [Page 23] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 [BCP100] Cotton, M., "Early IANA Allocation of Standards Track Code Points", BCP 100, RFC 7120, January 2014. [I-D.ietf-core-yang-cbor] Veillette, M., Petrov, I., Pelov, A., Bormann, C., and M. Richardson, "CBOR Encoding of Data Modeled with YANG", Work in Progress, Internet-Draft, draft-ietf-core-yang- cbor-17, 25 October 2021, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013, . [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG", RFC 7951, DOI 10.17487/RFC7951, August 2016, . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017, . 8.2. Informative References Veillette, et al. Expires 22 May 2022 [Page 24] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 [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-14, 25 October 2021, . [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, . [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, . [PYANG] Bjorklund, M., "An extensible YANG validator and converter in python", . [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, . [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, . [RFC7224] Bjorklund, M., "IANA Interface Type YANG Module", RFC 7224, DOI 10.17487/RFC7224, May 2014, . [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for Constrained-Node Networks", RFC 7228, DOI 10.17487/RFC7228, May 2014, . [RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for System Management", RFC 7317, DOI 10.17487/RFC7317, August 2014, . Veillette, et al. Expires 22 May 2022 [Page 25] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 [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, . [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018, . [RFC8343] Bjorklund, M., "A YANG Data Model for Interface Management", RFC 8343, DOI 10.17487/RFC8343, March 2018, . [RFC8344] Bjorklund, M., "A YANG Data Model for IP Management", RFC 8344, DOI 10.17487/RFC8344, March 2018, . [RFC8366] Watsen, K., Richardson, M., Pritikin, M., and T. Eckert, "A Voucher Artifact for Bootstrapping Protocols", RFC 8366, DOI 10.17487/RFC8366, May 2018, . 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", Veillette, et al. Expires 22 May 2022 [Page 26] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 "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" } ], "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 }, Veillette, et al. Expires 22 May 2022 [Page 27] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 { "namespace": "identity", "identifier": "radius-chap", "sid": 1705 }, { "namespace": "identity", "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", Veillette, et al. Expires 22 May 2022 [Page 28] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 "sid": 1714 }, { "namespace": "data", "identifier": "/ietf-system:set-current-datetime", "sid": 1715 }, { "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 Veillette, et al. Expires 22 May 2022 [Page 29] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 }, { "namespace": "data", "identifier": "/ietf-system:system-state/platform", "sid": 1724 }, { "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 }, Veillette, et al. Expires 22 May 2022 [Page 30] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 { "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 }, { "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", Veillette, et al. Expires 22 May 2022 [Page 31] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 "sid": 1741 }, { "namespace": "data", "identifier": "/ietf-system:system/dns-resolver", "sid": 1742 }, { "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/ Veillette, et al. Expires 22 May 2022 [Page 32] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 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 }, { "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", Veillette, et al. Expires 22 May 2022 [Page 33] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 "sid": 1759 }, { "namespace": "data", "identifier": "/ietf-system:system/ntp/server/prefer", "sid": 1760 }, { "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 }, { Veillette, et al. Expires 22 May 2022 [Page 34] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 "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", "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") Veillette, et al. Expires 22 May 2022 [Page 35] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 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. 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 Veillette, et al. Expires 22 May 2022 [Page 36] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 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. 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 7.4. 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 | Veillette, et al. Expires 22 May 2022 [Page 37] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 v v .-------------. +---------------+ +--> / Constrained \ yes | SID range | | \ application ? /---->| registration |<---------+ | '-----+-------' +------+--------+ | | | no | | | v v | | +---------------+ +---------------+ | +----+ YANG module | | SID sub-range | | | update | | assignment |<----------+ +---------------+ +-------+-------+ | | | 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. Veillette, et al. Expires 22 May 2022 [Page 38] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 +---------------+ 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 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. Veillette, et al. Expires 22 May 2022 [Page 39] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 Contributors Andy Bierman YumaWorks 685 Cochran St. Suite #160 Simi Valley, CA 93065 United States of America Email: andy@yumaworks.com Authors' Addresses 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 Universität Bremen TZI Postfach 330440 D-28359 Bremen Germany Veillette, et al. Expires 22 May 2022 [Page 40] Internet-Draft YANG Schema Item iDentifier (YANG SID) November 2021 Phone: +49-421-218-63921 Email: cabo@tzi.org Michael Richardson Sandelman Software Works Email: mcr+ietf@sandelman.ca Veillette, et al. 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