netmod M. Boucadair Internet-Draft Orange Updates: 8407, 8126 (if approved) 8 September 2022 Intended status: Standards Track Expires: 12 March 2023 Recommendations for Creating IANA-Maintained YANG Modules draft-boucadair-netmod-iana-registries-04 Abstract This document provides a set of guidelines for YANG module authors related to the design of IANA-maintained modules. These guidelines are meant to leverage existing IANA registries and use YANG as another format to present the content of these registries when appropriate. This document updates RFC 8407 by providing additional guidelines for IANA-maintained modules. Also, this document updates RFC 8126 by providing additional guidelines for writing the IANA considerations for RFCs that specify IANA-maintained modules. This document does not change anything written in RFC 8407 and RFC 8126. 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 12 March 2023. Copyright Notice Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved. Boucadair Expires 12 March 2023 [Page 1] Internet-Draft IANA-Maintained YANG Modules September 2022 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Guidelines for IANA-Maintained Modules . . . . . . . . . . . 3 4. Guidance for Writing the IANA Considerations for RFCs Defining IANA-Maintained Modules . . . . . . . . . . . . . . . . . 4 4.1. Template for IANA-Maintained Modules with Identities . . 5 4.2. Template for IANA-Maintained Modules with Enumerations . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.1. Normative References . . . . . . . . . . . . . . . . . . 8 8.2. Informative References . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction IANA maintains a set of registries that are key for interoperability. The content of these registries are usually available using various formats (e.g., plain text, XML). However, there were some confusion in the past about whether the content of some registries is dependent on a specific representation format. For example, Section 5 of [RFC8892] was published to clarify that MIB and YANG modules are merely additional formats in which the "Interface Types (ifType)" and "Tunnel Types (tunnelType)" registries are available. The MIB [RFC2863] and YANG modules [RFC7224][RFC8675] are not separate registries, and the same values are always present in all formats of the same registry. Also, some YANG modules include parameters and values directly in a module that is not maintained by IANA while these are populated in an IANA registry. Such a design is suboptimal as it creates another source of information that may deviate from the IANA registry as new values are assigned or some values are deprecated. Boucadair Expires 12 March 2023 [Page 2] Internet-Draft IANA-Maintained YANG Modules September 2022 For the sake of consistency, better flexibility to support new values, and maintaining IANA registries as the unique authoritative source of information, when such an information is maintained in a registry, this document encourages the use of IANA-maintained modules. Section 3 updates the guidelines in [RFC8407]. Also, Section 4 updates [RFC8407] and [RFC8126] by providing guidance for writing the IANA considerations for RFCs that specify IANA-maintained modules. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. This document makes use of the terms defined in Section 2 of [RFC8407]. 3. Guidelines for IANA-Maintained Modules When designing a YANG module for a functionality governed by a protocol for which IANA maintains a registry, it is RECOMMENDED to specify an IANA-maintained module that echoes the content of that registry. This is superior to including that content in an IETF- maintained module. When one or multiple sub-registries are available under the same registry, it is RECOMMENDED to define an IANA-maintained module for each sub-registry. However, module designers MAY consider defining one single IANA-maintained module that covers all sub-registries if maintaining that single module is manageable (e.g., very few values are present or expected to be present for each sub-registry). An example of such a module is documented in Section 5.2 of [RFC9132]. An IANA-maintained module may use identities (e.g., [RFC8675]) or enumerations (e.g., [RFC9108]). The decision about which type to use is left to the module designers and should be made based upon specifics related to the intended use of the IANA-maintained module. For example, identities are useful if the registry entries are organized hierarchically, possibly including multiple inheritances. It is RECOMMENDED that the reasoning for the design choice is documented in the companion specification that registers an IANA- maintained module. For example, [RFC9244] defines an IANA-maintained module that uses enumerations for the following reason: Boucadair Expires 12 March 2023 [Page 3] Internet-Draft IANA-Maintained YANG Modules September 2022 "The DOTS telemetry module (Section 10.1) uses "enumerations" rather than "identities" to define units, samples, and intervals because otherwise the namespace identifier "ietf-dots-telemetry" must be included when a telemetry attribute is included (e.g., in a mitigation efficacy update). The use of "identities" is thus suboptimal from a message compactness standpoint; one of the key requirements for DOTS messages." Designers of IANA-maintained modules MAY supply the full initial version of the module in a specification document that registers the module or only a script to be used (including by IANA) for generating the module (e.g., an XSLT stylesheet as in Appendix A of [RFC9108]). When a script is used, the Internet-Draft that defines an IANA- maintained module SHOULD include an appendix with the initial full version of the module. Including such an appendix in pre-RFC versions is meant to assess the correctness of the outcome of the supplied script. The authors MUST include a note to the RFC Editor requesting that the appendix be removed before publication as RFC. Initial versions of IANA-maintained modules that are published in RFCs may be misused despite the appropriate language to refer to the IANA registry to retrieve the up-to-date module. This is problematic for interoperability, e.g., when values are deprecated or are associated with a new meaning. Note: [Style] provides XSLT 1.0 stylesheets and other tools for translating IANA registries to YANG modules. The tools can be used to generate up-to-date revisions of an IANA-maintained module based upon the XML representation of an IANA registry. 4. Guidance for Writing the IANA Considerations for RFCs Defining IANA- Maintained Modules In addition to the IANA considerations in Section 3.8 of [RFC8407], the IANA Considerations Section of an RFC that includes an IANA- maintained module MUST provide the required instructions for IANA to automatically perform the maintenance of that IANA module. These instructions describe how to proceed with updates to the IANA- maintained module that are triggered by a change to the authoritative registry. Concretely, the IANA Considerations Section SHALL at least provide the following information: * An IANA request to add a note to the page displaying the information about the IANA-maintained module that new values must not be directly added to the module, but to an authoritative IANA registry. Boucadair Expires 12 March 2023 [Page 4] Internet-Draft IANA-Maintained YANG Modules September 2022 * An IANA request to add a note to the authoritative IANA registry to indicate that any change to the registry must be reflected into the corresponding IANA-maintained module. * Details about the required actions (e.g., add a new "identity" or "enum" statement) to update the IANA-maintained module to reflect changes to an authoritative IANA registry. Typically, these details have to include the procedure to create a new "identity" statement name and sub-statements ("base", "status", "description", and "reference") or a new "enum" statement and sub- statements ("value", "status", "description", and "reference"). * A note that unassigned or reserved values must not be present in the IANA-maintained module. * An indication whether experimental values are included in the IANA-maintained module. Absent such an indication, experimental values MUST NOT be listed in the IANA-maintained module. * An instruction about how to generate the "revision" statement. A template for the IANA Considerations is provided in Section 4.1 for IANA-maintained modules with identities and Section 4.2 for IANA- maintained modules with enumerations. Authors may modify the template to reflect specifics of their modules (e.g., Multiple registries can be listed for a single IANA-maintained module, no explicit description (or name) field is listed under the authoritative IANA registry). The following templates are to be considered in addition to the required information that is provided in Section 3.8 of [RFC8407]. 4.1. Template for IANA-Maintained Modules with Identities This document defines the initial version of the IANA-maintained "iana-foo" YANG module. The most recent version of the YANG module is available from the "YANG Parameters" registry [IANA-YANG-PARAMETERS]. IANA is requested to add this note to the registry: New values must not be directly added to the "iana-foo" YANG module. They must instead be added to the "foo" registry. Boucadair Expires 12 March 2023 [Page 5] Internet-Draft IANA-Maintained YANG Modules September 2022 When a value is added to the "foo" registry, a new "identity" statement must be added to the "iana-foo" YANG module. The name of the "identity" is the lower-case of the name provided in the registry. The "identity" statement should have the following sub- statements defined: "base": Contains 'name-base-identity-defined-in-foo'. "status": Include only if a registration has been deprecated or obsoleted. IANA "deprecated" maps to YANG status "deprecated", and IANA "obsolete" maps to YANG status "obsolete". "description": Replicates the description from the registry. "reference": Replicates the reference(s) from the registry with the title of the document(s) added. Unassigned or reserved values are not present in the module. When the "iana-foo" YANG module is updated, a new "revision" statement with a unique revision date must be added in front of the existing revision statements. IANA is requested to add this note to [reference-to-the-iana-foo- registry]: When this registry is modified, the YANG module "iana-foo" must be updated as defined in RFCXXXX. 4.2. Template for IANA-Maintained Modules with Enumerations This document defines the initial version of the IANA-maintained "iana-foo" YANG module. The most recent version of the YANG module is available from the "YANG Parameters" registry [IANA-YANG-PARAMETERS]. IANA is requested to add this note to the registry: New values must not be directly added to the "iana-foo" YANG module. They must instead be added to the "foo" registry. When a value is added to the "foo" registry, a new "enum" statement must be added to the "iana-foo" YANG module. The "enum" statement, and sub-statements thereof, should be defined: "enum": Replicates a name from the registry. Boucadair Expires 12 March 2023 [Page 6] Internet-Draft IANA-Maintained YANG Modules September 2022 "value": Contains the decimal value of the IANA-assigned value. "status": Is included only if a registration has been deprecated or obsoleted. IANA "deprecated" maps to YANG status "deprecated", and IANA "obsolete" maps to YANG status "obsolete". "description": Replicates the description from the registry. "reference": Replicates the reference(s) from the registry with the title of the document(s) added. Unassigned or reserved values are not present in the module. When the "iana-foo" YANG module is updated, a new "revision" statement with a unique revision date must be added in front of the existing revision statements. IANA is requested to add this note to [reference-to-the-iana-foo- registry]: When this registry is modified, the YANG module "iana-foo" must be updated as defined in RFCXXXX. 5. IANA Considerations This document does not require any IANA action. 6. Security Considerations This document does not introduce new concerns other than those already discussed in Section 15 of [RFC8407]. 7. Acknowledgements This document is triggered by a discussion the author had with Dhruv Dhody and Jensen Zhang. Thanks to Juergen Schoenwaelder, Ladislav Lhotka, and Qin Wu for the discussion and valuable comments. Special thanks to Ladislav Lhotka for sharing more context that led to the design documented in [RFC9108]. Thanks to Andy Bierman for the comments. Lou Berger suggested to include more details about IANA considerations. 8. References Boucadair Expires 12 March 2023 [Page 7] Internet-Draft IANA-Maintained YANG Modules September 2022 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, . [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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8407] Bierman, A., "Guidelines for Authors and Reviewers of Documents Containing YANG Data Models", BCP 216, RFC 8407, DOI 10.17487/RFC8407, October 2018, . 8.2. Informative References [IANA-YANG-PARAMETERS] IANA, "YANG Parameters", . [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, . [RFC7224] Bjorklund, M., "IANA Interface Type YANG Module", RFC 7224, DOI 10.17487/RFC7224, May 2014, . [RFC8675] Boucadair, M., Farrer, I., and R. Asati, "A YANG Data Model for Tunnel Interface Types", RFC 8675, DOI 10.17487/RFC8675, November 2019, . [RFC8892] Thaler, D. and D. Romascanu, "Guidelines and Registration Procedures for Interface Types and Tunnel Types", RFC 8892, DOI 10.17487/RFC8892, August 2020, . [RFC9108] Lhotka, L. and P. Špaček, "YANG Types for DNS Classes and Resource Record Types", RFC 9108, DOI 10.17487/RFC9108, September 2021, . Boucadair Expires 12 March 2023 [Page 8] Internet-Draft IANA-Maintained YANG Modules September 2022 [RFC9132] Boucadair, M., Ed., Shallow, J., and T. Reddy.K, "Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel Specification", RFC 9132, DOI 10.17487/RFC9132, September 2021, . [RFC9244] Boucadair, M., Ed., Reddy.K, T., Ed., Doron, E., Chen, M., and J. Shallow, "Distributed Denial-of-Service Open Threat Signaling (DOTS) Telemetry", RFC 9244, DOI 10.17487/RFC9244, June 2022, . [Style] IANA YANG, "IANA YANG", . Author's Address Mohamed Boucadair Orange 35000 Rennes France Email: mohamed.boucadair@orange.com Boucadair Expires 12 March 2023 [Page 9]