draft-ietf-netmod-yang-solutions-00.txt		draft-ietf-netmod-yang-solutions-01.txt
	Network Working Group R. Wilton, Ed.		Network Working Group R. Wilton, Ed.
	Internet-Draft Cisco Systems, Inc.		Internet-Draft Cisco Systems, Inc.
	Intended status: Informational March 17, 2020		Intended status: Informational 1 November 2020
	Expires: September 18, 2020		Expires: 5 May 2021
	YANG Versioning Solution Overview		YANG Versioning Solution Overview
	draft-ietf-netmod-yang-solutions-00		draft-ietf-netmod-yang-solutions-01
	Abstract		Abstract
	This document gives an overview of the different documents that		This document gives an overview of the different documents that
	comprise a full solution to the YANG versioning requirements		comprise a full solution to the YANG versioning requirements
	document. The purpose of this document is to help readers understand		document. The purpose of this document is to help readers understand
	how the discrete parts of the YANG versioning solution fit together		how the discrete parts of the YANG versioning solution fit together
	during working group development of the solution documents.		during working group development of the solution documents.
	Status of This Memo		Status of This Memo
	skipping to change at page 1, line 34 ¶		skipping to change at page 1, line 34 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on September 18, 2020.		This Internet-Draft will expire on 5 May 2021.
	Copyright Notice		Copyright Notice
	Copyright (c) 2020 IETF Trust and the persons identified as the		Copyright (c) 2020 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents (https://trustee.ietf.org/
	(https://trustee.ietf.org/license-info) in effect on the date of		license-info) in effect on the date of publication of this document.
	publication of this document. Please review these documents		Please review these documents carefully, as they describe your rights
	carefully, as they describe your rights and restrictions with respect		and restrictions with respect to this document. Code Components
	to this document. Code Components extracted from this document must		extracted from this document must include Simplified BSD License text
	include Simplified BSD License text as described in Section 4.e of		as described in Section 4.e of the Trust Legal Provisions and are
	the Trust Legal Provisions and are provided without warranty as		provided without warranty as described in the Simplified BSD License.
	described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Solution Documents . . . . . . . . . . . . . . . . . . . . . 3		2. Solution Documents . . . . . . . . . . . . . . . . . . . . . 3
	2.1. Updated YANG Module Revision Handling . . . . . . . . . . 3		2.1. Updated YANG Module Revision Handling . . . . . . . . . . 3
	2.2. YANG Semantic Versioning . . . . . . . . . . . . . . . . 4		2.2. YANG Semantic Versioning . . . . . . . . . . . . . . . . 4
	2.3. Versioned YANG packages . . . . . . . . . . . . . . . . . 4		2.3. Versioned YANG packages . . . . . . . . . . . . . . . . . 4
	2.4. Dynamic YANG schema selection . . . . . . . . . . . . . . 5		2.4. Dynamic YANG schema selection . . . . . . . . . . . . . . 5
	2.5. YANG Schema Comparison . . . . . . . . . . . . . . . . . 6		2.5. YANG Schema Comparison . . . . . . . . . . . . . . . . . 6
	3. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6		3. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
	4. Security Considerations . . . . . . . . . . . . . . . . . . . 7		4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
	6. References . . . . . . . . . . . . . . . . . . . . . . . . . 7		6. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
	6.1. Normative References . . . . . . . . . . . . . . . . . . 7		6.1. Normative References . . . . . . . . . . . . . . . . . . 7
	6.2. Informative References . . . . . . . . . . . . . . . . . 8		6.2. Informative References . . . . . . . . . . . . . . . . . 7
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
	1. Introduction		1. Introduction
	[I-D.ietf-netmod-yang-versioning-reqs] documents the requirements for		[I-D.ietf-netmod-yang-versioning-reqs] documents the requirements for
	any solution to the YANG [RFC7950] versioning problem. In		any solution to the YANG [RFC7950] versioning problem. In
	particular, chapter 5 lists the formal requirements that a solution		particular, chapter 5 lists the formal requirements that a solution
	requires.		requires.
	The complete solution to all of the YANG versioning requirements is		The complete solution to all of the YANG versioning requirements is
	comprised of five documents, each addressing different aspects of the		comprised of five documents, each addressing different aspects of the
	solution. These documents are:		solution. These documents are:
	1. [I-D.verdt-netmod-yang-module-versioning]		1. [I-D.ietf-netmod-yang-module-versioning]
	2. [I-D.verdt-netmod-yang-semver]		2. [I-D.ietf-netmod-yang-semver]
	3. [I-D.rwilton-netmod-yang-packages]		3. [I-D.ietf-netmod-yang-packages]
	4. [I-D.wilton-netmod-yang-ver-selection]		4. [I-D.ietf-netmod-yang-ver-selection]
	5. [I-D.verdt-netmod-yang-schema-comparison]		5. [I-D.ietf-netmod-yang-schema-comparison]
	The aim of this document is to help readers understand how these		The aim of this document is to help readers understand how these
	different solution documents fit together, and also which documents		different solution documents fit together, and also which documents
	contribute solutions that address particular individual requirements.		contribute solutions that address particular individual requirements.
	Open issues, across all of the solution documents are tracked at		Open issues, across all of the solution documents are tracked at
	<https://github.com/netmod-wg/yang-ver-dt/issues>.		https://github.com/netmod-wg/yang-ver-dt/issues.
	2. Solution Documents		2. Solution Documents
	2.1. Updated YANG Module Revision Handling		2.1. Updated YANG Module Revision Handling
	In summary, [I-D.verdt-netmod-yang-module-versioning] specifies		In summary, [I-D.ietf-netmod-yang-module-versioning] specifies
	minimal extensions and updates to the YANG language, YANG Library,		minimal extensions and updates to the YANG language, YANG Library,
	and YANG author guidelines to provide more flexible YANG module		and YANG author guidelines to provide more flexible YANG module
	revision handling. The intent is that these changes and extensions		revision handling. The intent is that these changes and extensions
	could be folded into future revisions of the updated specifications.		could be folded into future revisions of the updated specifications.
	The document provides a base solution for all requirements except Req		The document provides a base solution for all requirements except Req
	2.2, Req 3.1 and Req 3.2.		2.2, Req 3.1 and Req 3.2.
	The extensions and changes in the document can be summarized thus:		The extensions and changes in the document can be summarized thus:
	o It defines a YANG extension statement to indicate where non-		* It defines a YANG extension statement to indicate where non-
	backwards-compatible changes have occurred in a module's revision		backwards-compatible changes have occurred in a module's revision
	history.		history.
	o It relaxes the rules for the module revision history to allow for		* It relaxes the rules for the module revision history to allow for
	a non-linear module revision history. I.e., any given module		a non-linear module revision history. I.e., any given module
	revision may have multiple revisions directly derived from it.		revision may have multiple revisions directly derived from it.
	o It defines a new import extension statement that restricts the		* It defines a new import extension statement that restricts the
	allowed module revisions that satisfy the import to only those		allowed module revisions that satisfy the import to only those
	derived from a specified module revision.		derived from a specified module revision.
	o It defines a revision label extension statement to allow an		* It defines a revision label extension statement to allow an
	informative name to be associated with a particular revision date,		informative name to be associated with a particular revision date,
	and to be used in import statements, YANG module filenames, and is		and to be used in import statements, YANG module filenames, and is
	available in YANG library. One example of how the revision label		available in YANG library. One example of how the revision label
	could be used is to associate a semantic versioning scheme to YANG		could be used is to associate a semantic versioning scheme to YANG
	module revisions.		module revisions.
	o It updates the YANG rules for changes between module revisions		* It updates the YANG rules for changes between module revisions
	that are allowed to be classified as backwards-compatible. In		that are allowed to be classified as backwards-compatible. In
	particular, marking a node as obsolete is no longer classified as		particular, marking a node as obsolete is no longer classified as
	a backwards compatible change.		a backwards compatible change.
	o It provides updated guidance on how servers handle deprecated and		* It provides updated guidance on how servers handle deprecated and
	obsolete YANG nodes and augments YANG library with additional		obsolete YANG nodes and augments YANG library with additional
	leaves to report the server's behavior to clients.		leaves to report the server's behavior to clients.
	o It provides an extension statement to allow a description		* It provides an extension statement to allow a description
	statement to be associated with a YANG status statement, providing		statement to be associated with a YANG status statement, providing
	more information about why the status has changed.		more information about why the status has changed.
	o It defines how versioning relates to YANG instance data.		* It defines how versioning relates to YANG instance data.
	o It refines the guidelines for updating modules, taking into		* It refines the guidelines for updating modules, taking into
	consideration that non-backwards-compatible changes are sometimes		consideration that non-backwards-compatible changes are sometimes
	necessary for various pragmatic reasons.		necessary for various pragmatic reasons.
	2.2. YANG Semantic Versioning		2.2. YANG Semantic Versioning
	[I-D.verdt-netmod-yang-semver] defines a semantic versioning scheme,		[I-D.ietf-netmod-yang-semver] defines a semantic versioning scheme,
	derived from the semver.org 2.0.0 specification, that can be used in		derived from the semver.org 2.0.0 specification, that can be used in
	conjunction with the revision label extension statement defined in		conjunction with the revision label extension statement defined in
	Section 2.1 to allow semantic version numbers to be used to manage		Section 2.1 to allow semantic version numbers to be used to manage
	the revision lifecycle of YANG modules and other related YANG assets,		the revision lifecycle of YANG modules and other related YANG assets,
	e.g., YANG packages. This document provides an enhanced solution for		e.g., YANG packages. This document provides an enhanced solution for
	Req 2.1, but organizations authoring modules are not obliged to use		Req 2.1, but organizations authoring modules are not obliged to use
	this specific versioning scheme, and could choose a different		this specific versioning scheme, and could choose a different
	overlaid versioning scheme, or none at all and rely solely on		overlaid versioning scheme, or none at all and rely solely on
	revision dates.		revision dates.
	The aims of the YANG semantic versioning scheme are:		The aims of the YANG semantic versioning scheme are:
	o to generally allow clients to determine whether NBC changes have		* to generally allow clients to determine whether NBC changes have
	occurred between two revisions from the version number alone,		occurred between two revisions from the version number alone,
	without having to check the full revision history;		without having to check the full revision history;
	o to give a more informative identifier for a branched revision		* to give a more informative identifier for a branched revision
	history over revision dates alone;		history over revision dates alone;
	o to allow revision branches that contain fixes for published non-		* to allow revision branches that contain fixes for published non-
	latest releases.		latest releases.
	2.3. Versioned YANG packages		2.3. Versioned YANG packages
	The two previous solution documents primarily address version and		The two previous solution documents primarily address version and
	revision management of individual modules.		revision management of individual modules.
	[I-D.rwilton-netmod-yang-packages] provides a mechanism to group sets		[I-D.ietf-netmod-yang-packages] provides a mechanism to group sets of
	of related YANG modules revisions together, into constructs called		related YANG modules revisions together, into constructs called YANG
	YANG packages, and to apply a versioning scheme to the groups.		packages, and to apply a versioning scheme to the groups.
	The core part of this document are YANG module definitions that		The core part of this document are YANG module definitions that
	define a YANG package. The definitions are used as an augmentation		define a YANG package. The definitions are used as an augmentation
	to YANG library and also in YANG instance data documents for offline		to YANG library and also in YANG instance data documents for offline
	access.		access.
	The principle aims of YANG packages are:		The principle aims of YANG packages are:
	To define an efficient hierarchical structure that can precisely		To define an efficient hierarchical structure that can precisely
	specify a YANG schema.		specify a YANG schema.
	skipping to change at page 5, line 27 ¶		skipping to change at page 5, line 27 ¶
	To define constructs that can be used for YANG schema selection.		To define constructs that can be used for YANG schema selection.
	Although the YANG packages document does not satisfy any versioning		Although the YANG packages document does not satisfy any versioning
	requirements directly, it provides foundational building blocks for		requirements directly, it provides foundational building blocks for
	the schema selection solution, described in Section 2.4, that does		the schema selection solution, described in Section 2.4, that does
	address two of the requirements.		address two of the requirements.
	2.4. Dynamic YANG schema selection		2.4. Dynamic YANG schema selection
	[I-D.wilton-netmod-yang-ver-selection] specifies a solution for		[I-D.ietf-netmod-yang-ver-selection] specifies a solution for
	requirements 3.1 and 3.2 via the use of		requirements 3.1 and 3.2 via the use of
	[I-D.rwilton-netmod-yang-packages] and a model and protocol based		[I-D.ietf-netmod-yang-packages] and a model and protocol based schema
	schema selection scheme that can be used by clients to choose which		selection scheme that can be used by clients to choose which schemas
	schemas to use when interacting with the device from the available		to use when interacting with the device from the available schema
	schema that are supported and advertised by the server.		that are supported and advertised by the server.
	The dynamic YANG schema selection solution:		The dynamic YANG schema selection solution:
	allows servers to define named 'schema-sets' which specify the		allows servers to define named 'schema-sets' which specify the
	schema for each supported datastore via references to YANG		schema for each supported datastore via references to YANG
	packages;		packages;
	can support clients choosing a single default schema-set (from		can support clients choosing a single default schema-set (from
	those advertised by the server) that is used for all NETCONF/		those advertised by the server) that is used for all NETCONF/
	RESTCONF protocol sessions;		RESTCONF protocol sessions;
	skipping to change at page 6, line 15 ¶		skipping to change at page 6, line 15 ¶
	native vendor, or OpenConfig);		native vendor, or OpenConfig);
	allows considerable freedom in the schema selection capabilities		allows considerable freedom in the schema selection capabilities
	that servers choose to support.		that servers choose to support.
	2.5. YANG Schema Comparison		2.5. YANG Schema Comparison
	The final piece of the solution jigsaw is a document that describes		The final piece of the solution jigsaw is a document that describes
	how to algorithmically compare YANG schema, addressing Req 2.2.		how to algorithmically compare YANG schema, addressing Req 2.2.
	[I-D.verdt-netmod-yang-schema-comparison] specifies an algorithm that		[I-D.ietf-netmod-yang-schema-comparison] specifies an algorithm that
	can be used to compare two revisions of a YANG schema to determine		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,		the overall scope of the changes, and a list of the specific changes,
	between the two revisions.		between the two revisions.
	The YANG Schema Comparison solution:		The YANG Schema Comparison solution:
	defines a algorithm for comparing two YANG schema, identifying the		defines a algorithm for comparing two YANG schema, identifying the
	differences and classifying them as backwards-compatible, non-		differences and classifying them as backwards-compatible, non-
	backwards-compatible or editorial;		backwards-compatible or editorial;
	skipping to change at page 6, line 48 ¶		skipping to change at page 6, line 48 ¶
	would otherwise be ambiguous to a simple programmatic comparison		would otherwise be ambiguous to a simple programmatic comparison
	algorithm.		algorithm.
	3. Contributors		3. Contributors
	This document grew out of the YANG module versioning design team that		This document grew out of the YANG module versioning design team that
	started after IETF 101. The following individuals are (or have been)		started after IETF 101. The following individuals are (or have been)
	members of that design team and have contributed to defining the		members of that design team and have contributed to defining the
	problem, specifying the requirements, and working on a solution:		problem, specifying the requirements, and working on a solution:
	o Balazs Lengyel		* Balazs Lengyel
	o Benoit Claise		* Benoit Claise
	o Ebben Aries		* Ebben Aries
	o Jason Sterne		* Jason Sterne
	o Joe Clarke		* Joe Clarke
	o Juergen Schoenwaelder		* Juergen Schoenwaelder
	o Mahesh Jethanandani		* Mahesh Jethanandani
	o Michael (Wangzitao)		* Michael (Wangzitao)
	o Qin Wu		* Qin Wu
	o Reshad Rahman		* Reshad Rahman
	o Rob Wilton		* Rob Wilton
	o Susan Hares		* Susan Hares
	o Wu Bo		* Wu Bo
	4. Security Considerations		4. Security Considerations
	The document does not define any new protocol or data model. There		The document does not define any new protocol or data model. There
	is no security impact.		is no security impact.
	5. IANA Considerations		5. IANA Considerations
	None.		None.
	6. References		6. References
	6.1. Normative References		6.1. Normative References
	[I-D.ietf-netmod-yang-versioning-reqs]		[I-D.ietf-netmod-yang-versioning-reqs]
	Clarke, J., "YANG Module Versioning Requirements", draft-		Clarke, J., "YANG Module Versioning Requirements", Work in
	ietf-netmod-yang-versioning-reqs-02 (work in progress),		Progress, Internet-Draft, draft-ietf-netmod-yang-
	December 2019.		versioning-reqs-03, 29 June 2020,
			<https://tools.ietf.org/html/draft-ietf-netmod-yang-
			versioning-reqs-03>.
	[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",		[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
	RFC 7950, DOI 10.17487/RFC7950, August 2016,		RFC 7950, DOI 10.17487/RFC7950, August 2016,
	<https://www.rfc-editor.org/info/rfc7950>.		<https://www.rfc-editor.org/info/rfc7950>.
	6.2. Informative References		6.2. Informative References
	[I-D.rwilton-netmod-yang-packages]		[I-D.ietf-netmod-yang-module-versioning]
	Wilton, R., Rahman, R., Clarke, J., Sterne, J., and W. Bo,		Wilton, R., Rahman, R., Lengyel, B., Clarke, J., Sterne,
	"YANG Packages", draft-rwilton-netmod-yang-packages-03		J., Claise, B., and K. D'Souza, "Updated YANG Module
	(work in progress), February 2020.		Revision Handling", Work in Progress, Internet-Draft,
			draft-ietf-netmod-yang-module-versioning-01, 10 July 2020,
			<https://tools.ietf.org/html/draft-ietf-netmod-yang-
			module-versioning-01>.
	[I-D.verdt-netmod-yang-module-versioning]		[I-D.ietf-netmod-yang-packages]
	Claise, B., Clarke, J., Rahman, R., Wilton, R., Lengyel,		Wilton, R., Rahman, R., Clarke, J., Sterne, J., and W. Bo,
	B., Sterne, J., and K. D'Souza, "Updated YANG Module		"YANG Packages", Work in Progress, Internet-Draft, draft-
	Revision Handling", draft-verdt-netmod-yang-module-		ietf-netmod-yang-packages-00, 17 March 2020,
	versioning-01 (work in progress), October 2019.		<https://tools.ietf.org/html/draft-ietf-netmod-yang-
			packages-00>.
	[I-D.verdt-netmod-yang-schema-comparison]		[I-D.ietf-netmod-yang-schema-comparison]
	Wilton, R., "YANG Schema Comparison", draft-verdt-netmod-		Wilton, R., "YANG Schema Comparison", Work in Progress,
	yang-schema-comparison-00 (work in progress), November		Internet-Draft, draft-ietf-netmod-yang-schema-comparison-
	2019.		00, 17 March 2020, <https://tools.ietf.org/html/draft-
			ietf-netmod-yang-schema-comparison-00>.
	[I-D.verdt-netmod-yang-semver]		[I-D.ietf-netmod-yang-semver]
	Claise, B., Clarke, J., Rahman, R., Wilton, R., Lengyel,		Claise, B., Clarke, J., Rahman, R., Wilton, R., Lengyel,
	B., Sterne, J., and K. D'Souza, "YANG Semantic		B., Sterne, J., and K. D'Souza, "YANG Semantic
	Versioning", draft-verdt-netmod-yang-semver-01 (work in		Versioning", Work in Progress, Internet-Draft, draft-ietf-
	progress), October 2019.		netmod-yang-semver-01, 13 July 2020,
			<https://tools.ietf.org/html/draft-ietf-netmod-yang-
			semver-01>.
	[I-D.wilton-netmod-yang-ver-selection]		[I-D.ietf-netmod-yang-ver-selection]
	Wilton, R., Rahman, R., Clarke, J., Sterne, J., and W. Bo,		Wilton, R., Rahman, R., Clarke, J., Sterne, J., and W. Bo,
	"YANG Schema Selection", draft-wilton-netmod-yang-ver-		"YANG Schema Selection", Work in Progress, Internet-Draft,
	selection-02 (work in progress), February 2020.		draft-ietf-netmod-yang-ver-selection-00, 17 March 2020,
			<https://tools.ietf.org/html/draft-ietf-netmod-yang-ver-
			selection-00>.
	Author's Address		Author's Address
	Robert Wilton (editor)		Robert Wilton (editor)
	Cisco Systems, Inc.		Cisco Systems, Inc.
	Email: rwilton@cisco.com		Email: rwilton@cisco.com
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