YANG Module Versioning Requirements
draft-ietf-netmod-yang-versioning-reqs-03
Network Working Group J. Clarke, Ed.
Internet-Draft Cisco Systems, Inc.
Intended status: Informational June 29, 2020
Expires: December 31, 2020
YANG Module Versioning Requirements
draft-ietf-netmod-yang-versioning-reqs-03
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
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 December 31, 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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 Simplified BSD License text as described in Section 4.e of
Clarke Expires December 31, 2020 [Page 1]
Internet-Draft YANG Versioning Requirements June 2020
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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."
Clarke Expires December 31, 2020 [Page 2]
Internet-Draft YANG Versioning Requirements June 2020
2. "Note that definitions contained in a module are available to be
imported by any other module and are referenced in "import"
Show full document text