New YANG Module Update Procedure
draft-clacla-netmod-yang-model-update-04

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Network Working Group                                          B. Claise
Internet-Draft                                                 J. Clarke
Updates: 7950 (if approved)                          Cisco Systems, Inc.
Intended status: Standards Track                              B. Lengyel
Expires: November 16, 2018                                      Ericsson
                                                              K. D'Souza
                                                                    AT&T
                                                            May 15, 2018

                    New YANG Module Update Procedure
                draft-clacla-netmod-yang-model-update-04

Abstract

   This document specifies a new YANG module update procedure in case of
   backward-incompatible changes, as an alternative proposal to the YANG
   1.1 specifications.  This document updates RFC 7950.

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   Copyright (c) 2018 IETF Trust and the persons identified as the
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Claise, et al.          Expires November 16, 2018               [Page 1]
Internet-Draft                YANG Catalog                      May 2018

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  The Problems  . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Slow Standardization  . . . . . . . . . . . . . . . . . .   3
     2.2.  Some YANG Modules Are Not Backward Compatible . . . . . .   3
     2.3.  Non-Backward Compatible Errors  . . . . . . . . . . . . .   4
     2.4.  YANG Module Transition Strategy . . . . . . . . . . . . .   4
     2.5.  Need to Allow Non-Backward Compatible changes . . . . . .   5
     2.6.  Clear Indication of Node Support  . . . . . . . . . . . .   5
     2.7.  No way to easily decide whether a change is Backward
           Compatible  . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  The Solution  . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Semantic Versioning . . . . . . . . . . . . . . . . . . .   7
       3.1.1.  The Derived Semantic Version  . . . . . . . . . . . .   9
       3.1.2.  Import by Semantic Version  . . . . . . . . . . . . .  10
     3.2.  Updates to YANG 1.1 Module Update Rules . . . . . . . . .  13
     3.3.  Updates to ietf-yang-library  . . . . . . . . . . . . . .  13
     3.4.  Deprecated and Obsolete Reasons . . . . . . . . . . . . .  14
   4.  Semantic Version Extension YANG Module  . . . . . . . . . . .  15
   5.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  19
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  19
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
     7.1.  YANG Module Registrations . . . . . . . . . . . . . . . .  19
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  19
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  19
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  20
   Appendix A.  Appendix . . . . . . . . . . . . . . . . . . . . . .  20
     A.1.  Open Issues . . . . . . . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

1.  Introduction

   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
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