YANG Module Versioning Requirements
draft-ietf-netmod-yang-versioning-reqs-02
Network Working Group J. Clarke, Ed.
Internet-Draft Cisco Systems, Inc.
Intended status: Informational December 30, 2019
Expires: July 2, 2020
YANG Module Versioning Requirements
draft-ietf-netmod-yang-versioning-reqs-02
Abstract
This document describes the problems that can arise because of the
YANG language module update rules, that require all updates to YANG
module preserve strict backwards compatibility. It also defines the
requirements on any solution designed to solve the stated problems.
This document does not consider possible solutions, nor endorse any
particular solution.
Status of This Memo
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This Internet-Draft will expire on July 2, 2020.
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Internet-Draft YANG Versioning Requirements December 2019
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.1. Striving for model perfection . . . . . . . . . . . . . . 3
2.2. Some YANG Modules Are Not Backwards-Compatible . . . . . 3
2.3. Non-Backwards-Compatible Errors . . . . . . . . . . . . . 4
2.4. No way to easily decide whether a change is Backwards-
Compatible . . . . . . . . . . . . . . . . . . . . . . . 4
2.5. No good way to specify which module revision to import . 5
2.6. Early Warning about Removal . . . . . . . . . . . . . . . 6
2.7. Clear Indication of Node Support . . . . . . . . . . . . 6
3. Terminology and Conventions . . . . . . . . . . . . . . . . . 7
4. The Problem Statement . . . . . . . . . . . . . . . . . . . . 7
5. Requirements of a YANG Versioning Solution . . . . . . . . . 9
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 11
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
10.1. Normative References . . . . . . . . . . . . . . . . . . 12
10.2. Informative References . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
This requirements document initially considers some of the existing
YANG module update rules, then describes the problems that arise due
to those rules embracing strict backwards compatibility, and finally
defines requirements on any solution that may be designed to solve
these problems by providing an alternative YANG versioning strategy.
2. Background
The YANG data modeling language [RFC7950] specifies strict rules for
updating YANG modules (see section 11 "Updating a Module"). Citing a
few of the relevant rules:
1. "As experience is gained with a module, it may be desirable to
revise that module. However, changes to published modules are
not allowed if they have any potential to cause interoperability
problems between a client using an original specification and a
server using an updated specification."
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2. "Note that definitions contained in a module are available to be
imported by any other module and are referenced in "import"
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