Network Working Group R. Wilton, Ed.
Internet-Draft Cisco Systems, Inc.
Intended status: Informational March 19, 2020
Expires: September 20, 2020

YANG Versioning Solution Overview


This document gives an overview of the different documents that comprise a full solution to the YANG versioning requirements document. The purpose of this document is to help readers understand how the discrete parts of the YANG versioning solution fit together during working group development of the solution documents.

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Table of Contents

1. Introduction

[I-D.ietf-netmod-yang-versioning-reqs] documents the requirements for any solution to the YANG [RFC7950] versioning problem. In particular, chapter 5 lists the formal requirements that a solution requires.

The complete solution to all of the YANG versioning requirements is comprised of five documents, each addressing different aspects of the solution. These documents are:

  1. [I-D.verdt-netmod-yang-module-versioning]
  2. [I-D.verdt-netmod-yang-semver]
  3. [I-D.rwilton-netmod-yang-packages]
  4. [I-D.wilton-netmod-yang-ver-selection]
  5. [I-D.verdt-netmod-yang-schema-comparison]

The aim of this document is to help readers understand how these different solution documents fit together, and also which documents contribute solutions that address particular individual requirements.

Open issues, across all of the solution documents are tracked at <>.

2. Solution Documents

2.1. Updated YANG Module Revision Handling

In summary, [I-D.verdt-netmod-yang-module-versioning] specifies minimal extensions and updates to the YANG language, YANG Library, and YANG author guidelines to provide more flexible YANG module revision handling. The intent is that these changes and extensions could be folded into future revisions of the updated specifications. The document provides a base solution for all requirements except Req 2.2, Req 3.1 and Req 3.2.

The extensions and changes in the document can be summarized thus:

2.2. YANG Semantic Versioning

[I-D.verdt-netmod-yang-semver] defines a semantic versioning scheme, derived from the 2.0.0 specification, that can be used in conjunction with the revision label extension statement defined in Section 2.1 to allow semantic version numbers to be used to manage the revision lifecycle of YANG modules and other related YANG assets, e.g., YANG packages. This document provides an enhanced solution for Req 2.1, but organizations authoring modules are not obliged to use this specific versioning scheme, and could choose a different overlaid versioning scheme, or none at all and rely solely on revision dates.

The aims of the YANG semantic versioning scheme are:

2.3. Versioned YANG packages

The two previous solution documents primarily address version and revision management of individual modules. [I-D.rwilton-netmod-yang-packages] provides a mechanism to group sets of related YANG modules revisions together, into constructs called YANG packages, and to apply a versioning scheme to the groups.

The core part of this document are YANG module definitions that define a YANG package. The definitions are used as an augmentation to YANG library and also in YANG instance data documents for offline access.

The principle aims of YANG packages are:

Although the YANG packages document does not satisfy any versioning requirements directly, it provides foundational building blocks for the schema selection solution, described in Section 2.4, that does address two of the requirements.

2.4. Dynamic YANG schema selection

[I-D.wilton-netmod-yang-ver-selection] specifies a solution for requirements 3.1 and 3.2 via the use of [I-D.rwilton-netmod-yang-packages] and a model and protocol based schema selection scheme that can be used by clients to choose which schemas to use when interacting with the device from the available schema that are supported and advertised by the server.

The dynamic YANG schema selection solution:

2.5. YANG Schema Comparison

The final piece of the solution jigsaw is a document that describes how to algorithmically compare YANG schema, addressing Req 2.2.

[I-D.verdt-netmod-yang-schema-comparison] specifies an algorithm that can be used to compare two revisions of a YANG schema to determine the overall scope of the changes, and a list of the specific changes, between the two revisions.

The YANG Schema Comparison solution:

3. Contributors

This document grew out of the YANG module versioning design team that started after IETF 101. The following individuals are (or have been) members of that design team and have contributed to defining the problem, specifying the requirements, and working on a solution:

4. Security Considerations

The document does not define any new protocol or data model. There is no security impact.

5. IANA Considerations


6. References

6.1. Normative References

[I-D.ietf-netmod-yang-versioning-reqs] Clarke, J., "YANG Module Versioning Requirements", Internet-Draft draft-ietf-netmod-yang-versioning-reqs-02, December 2019.
[RFC7950] Bjorklund, M., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016.

6.2. Informative References

[I-D.rwilton-netmod-yang-packages] Wilton, R., Rahman, R., Clarke, J., Sterne, J. and W. Bo, "YANG Packages", Internet-Draft draft-rwilton-netmod-yang-packages-03, February 2020.
[I-D.verdt-netmod-yang-module-versioning] Claise, B., Clarke, J., Rahman, R., Wilton, R., Lengyel, B., Sterne, J. and K. D'Souza, "Updated YANG Module Revision Handling", Internet-Draft draft-verdt-netmod-yang-module-versioning-01, October 2019.
[I-D.verdt-netmod-yang-schema-comparison] Wilton, R., "YANG Schema Comparison", Internet-Draft draft-verdt-netmod-yang-schema-comparison-00, November 2019.
[I-D.verdt-netmod-yang-semver] Claise, B., Clarke, J., Rahman, R., Wilton, R., Lengyel, B., Sterne, J. and K. D'Souza, "YANG Semantic Versioning", Internet-Draft draft-verdt-netmod-yang-semver-01, October 2019.
[I-D.wilton-netmod-yang-ver-selection] Wilton, R., Rahman, R., Clarke, J., Sterne, J. and W. Bo, "YANG Schema Selection", Internet-Draft draft-wilton-netmod-yang-ver-selection-02, February 2020.

Author's Address

Robert Wilton (editor) Cisco Systems, Inc. EMail: