YANG Semantic Versioning
draft-ietf-netmod-yang-semver-24
| Document | Type | Active Internet-Draft (netmod WG) | |
|---|---|---|---|
| Authors | Joe Clarke , Robert Wilton , Reshad Rahman , Balázs Lengyel , Jason Sterne , Benoît Claise | ||
| Last updated | 2026-03-04 (Latest revision 2025-09-29) | ||
| Replaces | draft-verdt-netmod-yang-semver | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Proposed Standard | ||
| Formats | |||
| Yang Validation | 0 errors, 0 warnings | ||
| Reviews |
OPSDIR IETF Last Call review
by Tony Li
Serious issues
YANGDOCTORS Early review
(of
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by Ebben Aries
Ready w/nits
GENART IETF Last Call Review due 2026-03-03
Incomplete
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Lou Berger | ||
| Shepherd write-up | Show Last changed 2026-02-16 | ||
| IESG | IESG state | Waiting for AD Go-Ahead::Revised I-D Needed | |
| Action Holders | |||
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| Send notices to | lberger@labn.net | ||
| IANA | IANA review state | IANA - Not OK |
draft-ietf-netmod-yang-semver-24
Network Working Group J. Clarke, Ed.
Internet-Draft R. Wilton, Ed.
Updates: 8407, 8525, 7950 (if approved) Cisco Systems, Inc.
Intended status: Standards Track R. Rahman
Expires: 2 April 2026 Equinix
B. Lengyel
Ericsson
J. Sterne
Nokia
B. Claise
Everything OPS
29 September 2025
YANG Semantic Versioning
draft-ietf-netmod-yang-semver-24
Abstract
This document specifies a YANG extension along with guidelines for
applying an extended set of semantic versioning rules to revisions of
YANG artifacts (e.g., modules and packages). Additionally, this
document defines a YANG extension for controlling module imports
based on these modified semantic versioning rules.
This document updates RFCs 7950, 8407bis, and 8525.
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 2 April 2026.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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 Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Updates to Other RFCs . . . . . . . . . . . . . . . . . . 3
1.2. Editorial Note (To be removed by RFC Editor) . . . . . . 3
2. Examples of How Versioning Is Applied To YANG Module
Revisions . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology and Conventions . . . . . . . . . . . . . . . . . 4
4. YANG Semantic Versioning . . . . . . . . . . . . . . . . . . 5
4.1. Relationship Between SemVer and YANG Semver . . . . . . . 5
4.2. YANG Semantic Version Extension . . . . . . . . . . . . . 5
4.3. YANG Semver Pattern . . . . . . . . . . . . . . . . . . . 5
4.4. Semantic Versioning Scheme for YANG Artifacts . . . . . . 6
4.4.1. YANG Semver with submodules . . . . . . . . . . . . . 8
4.4.2. Examples for YANG semantic versions . . . . . . . . . 9
4.4.3. Branching Limitations with YANG Semver . . . . . . . 11
4.5. YANG Semantic Version Update Rules . . . . . . . . . . . 11
4.6. Examples of the YANG Semver Version Identifier . . . . . 13
4.6.1. Example Module Using YANG Semver . . . . . . . . . . 13
4.6.2. Example of Package Using YANG Semver . . . . . . . . 15
5. Import Module by YANG Semantic Version . . . . . . . . . . . 16
5.1. The recommended-min-version Extension . . . . . . . . . . 16
5.2. Import by YANG Semantic Version Rules . . . . . . . . . . 17
6. Guidelines for Using YANG Semver During Module Development . 18
6.1. YANG Semver in IETF Modules . . . . . . . . . . . . . . . 19
6.1.1. YANG Semver in New IETF Modules . . . . . . . . . . . 19
6.1.2. YANG Semver when updating IETF Modules . . . . . . . 19
6.1.3. YANG Semver when there are multiple parallel competing
IETF drafts . . . . . . . . . . . . . . . . . . . . . 20
7. Updates to ietf-yang-library . . . . . . . . . . . . . . . . 21
7.1. YANG library versioning augmentations . . . . . . . . . . 21
7.1.1. Advertising version . . . . . . . . . . . . . . . . . 22
8. YANG Modules . . . . . . . . . . . . . . . . . . . . . . . . 22
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 27
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28
11. Security Considerations . . . . . . . . . . . . . . . . . . . 28
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
12.1. YANG Module Registrations . . . . . . . . . . . . . . . 29
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12.2. Guidance for YANG Semver in IANA maintained YANG modules
and submodules . . . . . . . . . . . . . . . . . . . . . 30
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
13.1. Normative References . . . . . . . . . . . . . . . . . . 30
13.2. Informative References . . . . . . . . . . . . . . . . . 31
Appendix A. Example IETF Module Development . . . . . . . . . . 33
Appendix B. Examples of _COMPAT Modifier Use . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36
1. Introduction
[I-D.ietf-netmod-yang-module-versioning] puts forth new concepts
relating to modified rules for updating YANG modules and submodules,
a means to signal when a new revision of a module or submodule has
non-backwards-compatible (NBC) changes compared to its previous
revision, and extends the YANG import statement with a minimum
revision suggestion to help document inter-module dependencies.
This document defines a YANG extension that tags a YANG artifact
(i.e., YANG modules, YANG submodules, and YANG packages
[I-D.ietf-netmod-yang-packages] ) with a version identifier that
adheres to extended semantic versioning rules [SemVer]. The goal
being to add a human readable version identifier that provides
compatibility information for the YANG artifact without needing to
compare or parse its body. The version identifier and rules defined
herein represent the recommended approach to apply versioning to IETF
YANG artifacts. This document defines augmentations to ietf-yang-
library to reflect the version of YANG modules within the module-set
data.
Note that a specific revision of the SemVer 2.0.0 specification is
referenced here (from June 19, 2020) to provide an immutable version.
This is because the 2.0.0 version of the specification has changed
over time without any change to the semantic version itself.
1.1. Updates to Other RFCs
This document updates [RFC7950] to clarify how ambiguous module
imports are resolved (Section 5). It updates [RFC8525] by adding a
version leaf to modules and submodules (Section 7). It updates
[I-D.ietf-netmod-rfc8407bis] to clarify how version statements are to
be added to modules and submodules (Section 6).
1.2. Editorial Note (To be removed by RFC Editor)
Note to the RFC Editor: This section is to be removed prior to
publication.
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This document updates [I-D.ietf-netmod-rfc8407bis]. The header
metadata for this document should be updated to the new RFC number
when [I-D.ietf-netmod-rfc8407bis] is published.
2. Examples of How Versioning Is Applied To YANG Module Revisions
The following diagram illustrates how the branched revision history
and the YANG Semver version extension statement could be used:
Example YANG module with branched revision history.
Module revision date Example version identifier
2019-01-01 <- 1.0.0
|
2019-02-01 <- 2.0.0
| \
2019-03-01 \ <- 3.0.0
| \
| 2019-04-01 <- 2.1.0
| |
2019-05-01 | <- 3.1.0
|
2019-06-01 <- 2.2.0
Figure 1
The tree diagram above illustrates how an example module's revision
history might evolve, over time.
3. Terminology and Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Additionally, this document uses the following terminology:
* YANG artifact: YANG modules, YANG submodules, and YANG packages
[I-D.ietf-netmod-yang-packages] are examples of YANG artifacts for
the purposes of this document.
* SemVer: A version string that corresponds to the rules defined in
[SemVer]. This specific camel-case notation is the one used by
the SemVer 2.0.0 website and used within this document to
distinguish between SemVer 2.0.0 and YANG Semver.
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* YANG Semver: A version identifier that is consistent with the
extended set of semantic versioning rules, based on [SemVer],
defined within this document.
4. YANG Semantic Versioning
This section defines YANG Semantic Versioning, explains how it is
used with YANG artifacts, and describes the rules associated with
changing an artifact's semantic version when its contents are
updated.
4.1. Relationship Between SemVer and YANG Semver
[SemVer] is completely compatible with YANG Semver in that a SemVer
semantic version number is legal according to the YANG Semver rules
(though the inverse is not necessarily true). YANG Semver is a
superset of the SemVer rules, and allows for limited branching within
YANG artifacts. If no branching occurs within a YANG artifact (i.e.,
you do not use the compatibility modifiers described below), the YANG
Semver version label will appear as a SemVer version number.
4.2. YANG Semantic Version Extension
The ietf-yang-semver module defines a "version" extension -- a
substatement to a module or submodule's "revision" statement -- that
takes a YANG semantic version as its argument and specifies the
version for the given module or submodule. The syntax for the YANG
semantic version is defined in a typedef in the same module and
described below.
4.3. YANG Semver Pattern
YANG artifacts that employ semantic versioning as defined in this
document MUST use a version identifier that corresponds to the
following pattern: 'X.Y.Z_COMPAT'. Where:
* X, Y and Z are mandatory non-negative integers that are each less
than or equal to 2147483647 (i.e., the maximum signed 32-bit
integer value) and MUST NOT contain leading zeroes,
* The '.' is a literal period (ASCII character 0x2e),
* The '_' is an optional single literal underscore (ASCII character
0x5f) and MUST only be present if the following COMPAT element is
included,
* COMPAT, if specified, MUST be either the literal string
"compatible" or the literal string "non_compatible".
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Additionally, [SemVer] defines two specific types of metadata that
may be appended to a semantic version string. Pre-release metadata
MAY be appended to a YANG Semver string after a trailing '-'
character. Build metadata MAY be appended after a trailing '+'
character. If both pre-release and build metadata are present, then
build metadata MUST follow pre-release metadata. While build
metadata MUST be ignored when comparing YANG semantic versions, pre-
release metadata can be used during module and submodule development
as specified in Section 6. Both pre-release and build metadata are
allowed in order to support all the [SemVer] rules. Thus, a version
lineage that follows strict [SemVer] rules is allowed for a YANG
artifact.
The ietf-yang-semver module included in this document defines an
extension to apply a YANG Semver identifier to a YANG artifact as
well as a typedef that formally specifies the syntax of the YANG
Semver.
4.4. Semantic Versioning Scheme for YANG Artifacts
This document defines the YANG semantic versioning scheme that is
used for YANG artifacts. The versioning identifier has the following
properties:
* The YANG semantic versioning scheme is extended from version 2.0.0
of the semantic versioning scheme defined at semver.org [SemVer]
to cover the additional requirements for the management of YANG
artifact lifecycles that cannot be addressed using the semver.org
2.0.0 versioning scheme alone.
* Unlike the [SemVer] versioning scheme, the YANG semantic
versioning scheme supports updates to older versions of YANG
artifacts, to allow for bug fixes and enhancements to artifact
versions that are not the latest. However, it does not provide
for the unlimited branching and updating of older revisions which
are documented by the general rules in
[I-D.ietf-netmod-yang-module-versioning].
* YANG artifacts that use the [SemVer] versioning scheme are fully
compatible with implementations that understand the YANG semantic
versioning scheme defined in this document.
* If updates are always restricted to the latest revision of the
artifact only, then the version identifiers used by the YANG
semantic versioning scheme are exactly the same as those defined
by the [SemVer] versioning scheme.
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Every YANG module and submodule versioned using the YANG semantic
versioning scheme specifies the module's or submodule's semantic
version as the argument to the 'ysv:version' statement.
Because the rules put forth in
[I-D.ietf-netmod-yang-module-versioning] are designed to work well
with existing versions of YANG and allow for artifact authors to
migrate to this scheme, it is not expected that all revisions of a
given YANG artifact will have a semantic version identifier. For
example, the first revision of a module or submodule may have been
produced before this scheme was available.
YANG packages that make use of this YANG Semver will reflect that in
the package metadata.
As stated above, the YANG semantic version is expressed as a string
of the form: 'X.Y.Z_COMPAT'.
* 'X' is the MAJOR version. Changes in the MAJOR version number
indicate changes that are non-backwards-compatible (Section 3.1.1
of [I-D.ietf-netmod-yang-module-versioning]) to versions with a
lower MAJOR version number.
* 'Y' is the MINOR version. Changes in the MINOR version number
indicate changes that are backwards-compatible to versions with
the same MAJOR version number, but a lower MINOR version number
and no "_compatible" or "_non_compatible" modifier.
* 'Z' is the PATCH version. Changes in the PATCH version number can
indicate an editorial change to the YANG artifact. In conjunction
with the '_COMPAT' modifier (see below) changes to 'Z' may
indicate a more substantive module change. An editorial change is
defined to be a change in the YANG artifact's content that does
not affect the semantic meaning or functionality provided by the
artifact in any way. Some examples include correcting a spelling
mistake in the description of a leaf within a YANG module or
submodule, non-significant whitespace changes (e.g., realigning
description statements or changing indentation), or changes to
YANG comments. Note: restructuring how a module uses, or does not
use, submodules is treated as an editorial level change on the
condition that there is no change in the module's semantic
behavior due to the restructuring.
* '_COMPAT' is an additional modifier, unique to YANG Semver (i.e.,
not valid in [SemVer] ), that indicates backwards-compatible, or
non-backwards-compatible changes relative to versions with the
same MAJOR and MINOR version numbers, but lower PATCH version
number, depending on what form modifier '_COMPAT' takes:
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- If the modifier string is absent, the change represents an
editorial change.
- If, however, the modifier string is present, the meaning is
described below:
- "_compatible" - the change represents a backwards-compatible
change
- "_non_compatible" - the change represents a non-backwards-
compatible change
The '_COMPAT' modifier string is "sticky". Once a revision of a
module has a modifier in the version identifier, then all subsequent
module versions in that branch (i.e., those with the same X.Y version
digits) will also have a modifier. The modifier can change from
"_compatible" to "_non_compatible" in a subsequent version, but the
modifier MUST NOT change from "_non_compatible" to "_compatible" and
MUST NOT be removed. The persistence of the "_non_compatible"
modifier ensures that comparisons of versions do not give the false
impression of compatibility between two potentially non-compatible
versions. If "_non_compatible" was removed, for example between
versions "3.3.2_non_compatible" and "3.3.3" (where "3.3.3" was simply
an editorial change), then comparing versions "3.3.3" to "3.0.0"
would look like they are backwards compatible when they are not
(since "3.3.2_non_compatible" was on the same MAJOR.MINOR branch and
introduced a non-backwards-compatible change).
The YANG artifact name and YANG semantic version uniquely identify a
revision of said artifact. There MUST NOT be multiple instances of a
YANG artifact definition with the same name and YANG semantic version
but different content (and in the case of modules and submodules,
different revision dates).
There MUST NOT be multiple versions of a YANG artifact that have the
same MAJOR, MINOR and PATCH version numbers, but different patch
modifier strings. E.g., artifact version "1.2.3_non_compatible" MUST
NOT be defined if artifact version "1.2.3" has already been defined.
4.4.1. YANG Semver with submodules
YANG Semver MAY be used to version submodules. Submodule versions
are separate of any version on the including module, but if a
submodule has changed, then the version of the including module MUST
also be updated.
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The rules for determining the version change of a submodule are the
same as those defined in Section 4.3 and Section 4.4 as applied to
YANG modules, except they only apply to the part of the module schema
defined within the submodule's file.
One interesting case is moving definitions from one submodule to
another in a way that does not change the resulting schema of the
including module. In this case:
1. The including module has editorial changes and must receive a new
version number with a PATCH component modification.
2. The submodule with the schema definition removed has non-
backwards-compatible changes and must receive a new version
number with a MAJOR component modification.
3. The submodule with the schema definitions added has backwards-
compatible changes and must receive a new version number with a
MINOR component modification.
Note that the meaning of a submodule may change drastically despite
having no changes in content or revision due to changes in other
submodules belonging to the same module (e.g. groupings and typedefs
declared in one submodule and used in another).
4.4.2. Examples for YANG semantic versions
The following diagram and explanation illustrate how YANG semantic
versions work.
YANG Semantic versions for an example module:
0.1.0
|
0.2.0
|
1.0.0
|
1.1.0 -> 1.1.1_compatible -> 1.1.2_non_compatible
|
1.2.0 -> 1.2.1_non_compatible -> 1.2.2_non_compatible
| \
2.0.0 \
| \--> 1.3.0 -> 1.3.1_non_compatible
3.0.0 |
| 1.4.0
3.1.0
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The tree diagram above illustrates how the version history might
evolve for an example module. The tree diagram only shows the
branching relationships between the versions. It does not describe
the chronology of the versions (i.e. when in time each version was
published relative to the other versions).
The following description lists an example of what the chronological
order of the versions could look like, from oldest version to newest:
0.1.0 - first pre-release module version
0.2.0 - second pre-release module version (with NBC changes)
1.0.0 - first release (may have NBC changes from 0.2.0)
1.1.0 - added new functionality, leaf "foo" (BC)
1.2.0 - added new functionality, leaf "baz" (BC)
2.0.0 - change existing model for performance reasons, e.g. re-key
list (NBC)
1.3.0 - improve existing functionality, added leaf "foo-64" (BC)
1.1.1_compatible - backport "foo-64" leaf to 1.1.x to avoid
implementing "baz" from 1.2.0. This revision was created after
1.2.0 otherwise it may have been released as 1.2.0. (BC)
3.0.0 - NBC bugfix, rename "baz" to "bar"; also add new BC leaf
"wibble"; (NBC)
1.3.1_non_compatible - backport NBC fix, rename "baz" to "bar"
(NBC)
1.2.1_non_compatible - backport NBC fix, rename "baz" to "bar"
(NBC)
1.1.2_non_compatible - NBC point bug fix, not required in 2.0.0
due to model changes (NBC)
1.4.0 - introduce new leaf "ghoti" (BC)
3.1.0 - introduce new leaf "wobble" (BC)
1.2.2_non_compatible - backport "wibble". This is a BC change but
"non_compatible" modifier is sticky. (BC)
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4.4.3. Branching Limitations with YANG Semver
YANG artifacts that use the YANG Semver version scheme MUST ensure
that two artifacts with the same MAJOR version number and no
_compatible or _non_compatible modifiers are backwards compatible.
Therefore, certain branching schemes cannot be used with YANG Semver.
For example, the following branching approach using the following
YANG Semver identifiers is not supported:
3.5.0 -- 3.6.0 (add leaf foo)
|
|
3.20.0 (added leaf bar)
In this case, given only the YANG Semver identifiers 3.6.0 and
3.20.0, one would assume that 3.20.0 is backwards compatible with
3.6.0. But in the illegal example above, 3.20.0 is not backwards
compatible with 3.6.0 since 3.20.0 does not contain the leaf foo.
Branching limitations should be carefully considered when doing
software development. It is recommended to avoid only incrementing
the PATCH digit on the main branch of YANG modules. See Appendix B
Scenario 2 for an illustration and explanation.
4.5. YANG Semantic Version Update Rules
When a new version of an artifact is produced, then the following
rules define how the YANG semantic version for the new artifact is
calculated, based on the changes between the two artifact versions,
and the YANG semantic version of the original artifact from which the
changes are derived.
The following four rules specify the RECOMMENDED, and REQUIRED
minimum, update to a YANG semantic version:
1. If an artifact is being updated in a non-backwards-compatible
way, then the artifact version
"X.Y.Z[_compatible|_non_compatible]" SHOULD be updated to
"X+1.0.0" unless that version has already been used for this
artifact but with different content, in which case the artifact
version "X.Y.Z+1_non_compatible" SHOULD be used instead.
2. If an artifact is being updated in a backwards-compatible way,
then the next version number depends on the format of the current
version number:
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i "X.Y.Z" - the artifact version SHOULD be updated to
"X.Y+1.0", unless that version has already been used for
this artifact but with different content, when the artifact
version SHOULD be updated to "X.Y.Z+1_compatible" instead.
ii "X.Y.Z_compatible" - the artifact version SHOULD be updated
to "X.Y.Z+1_compatible".
iii "X.Y.Z_non_compatible" - the artifact version SHOULD be
updated to "X.Y.Z+1_non_compatible".
3. If an artifact is being updated in an editorial way, then the
next version identifier depends on the format of the current
version identifier:
i "X.Y.Z" - the artifact version SHOULD be updated to
"X.Y.Z+1"
ii "X.Y.Z_compatible" - the artifact version SHOULD be updated
to "X.Y.Z+1_compatible".
iii "X.Y.Z_non_compatible" - the artifact version SHOULD be
updated to "X.Y.Z+1_non_compatible".
4. YANG artifact semantic version identifiers beginning with 0,
i.e., "0.X.Y", are regarded as pre-release definitions and need
not follow the rules above. Either the MINOR or PATCH version
numbers may be updated, regardless of whether the changes are
non-backwards-compatible, backwards-compatible, or editorial.
See Section 6 for more details on using this notation during
module and submodule development.
5. Additional pre-release rules for modules that have had at least
one release are specified in Section 6.
Although artifacts SHOULD be updated according to the rules above,
which specify the recommended (and minimum required) update to the
version identifier, the following rules MAY be applied when choosing
a new version identifier:
1. An artifact author MAY update the version identifier with a more
significant update than described by the rules above. For
example, an artifact could be given a new MAJOR version number
(i.e., X+1.0.0), even though no non-backwards-compatible changes
have occurred, or an artifact could be given a new MINOR version
number (i.e., X.Y+1.0) even if the changes were only editorial.
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2. An artifact author MAY skip versions. For example, a vendor
might have released 1.0.0 of a module for general availability.
Then, during subsequent development, used 1.1.0 and 1.2.0 for
internal releases. The next generally available release could be
1.3.0 where external users never see 1.1.0 or 1.2.0.
Although YANG Semver always indicates when a non-backwards-
compatible, or backwards-compatible change may have occurred to a
YANG artifact, it does not guarantee that such a change has occurred,
or that consumers of that YANG artifact will be impacted by the
change. Hence, tooling, e.g.,
[I-D.ietf-netmod-yang-schema-comparison], also plays an important
role for comparing YANG artifacts and calculating the likely impact
from changes.
[I-D.ietf-netmod-yang-module-versioning] defines the "rev:non-
backwards-compatible" extension statement to indicate where non-
backwards-compatible changes have occurred in the module revision
history. If a revision entry in a module's revision history includes
the "rev:non-backwards-compatible" statement then that MUST be
reflected in any YANG semantic version associated with that revision.
However, the reverse does not necessarily hold, i.e., if the MAJOR
version has been incremented it does not necessarily mean that a
"rev:non-backwards-compatible" statement would be present.
4.6. Examples of the YANG Semver Version Identifier
4.6.1. Example Module Using YANG Semver
Below is a sample YANG module that uses YANG Semver based on the
rules defined in this document.
module example-versioned-module {
yang-version 1.1;
namespace "urn:example:versioned:module";
prefix "exvermod";
import ietf-yang-revisions { prefix "rev"; }
import ietf-yang-semver { prefix "ysv"; }
description
"to be completed";
revision 2017-08-30 {
description "Backport 'wibble' leaf";
ysv:version 1.2.2_non_compatible;
}
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revision 2017-07-30 {
description "Rename 'baz' to 'bar'";
ysv:version 1.2.1_non_compatible;
rev:non-backwards-compatible;
}
revision 2017-04-20 {
description "Add new functionality, leaf 'baz'";
ysv:version 1.2.0;
}
revision 2017-04-03 {
description "Add new functionality, leaf 'foo'";
ysv:version 1.1.0;
}
revision 2017-02-07 {
description "First release version.";
ysv:version 1.0.0;
}
// Note: YANG Semver rules do not apply to 0.X.Y labels.
// The following pre-release revision statements would not
// appear in any final published version of a module. They
// are removed when the final version is published.
// During the pre-release phase of development, only a
// single one of these revision statements would appear
// revision 2017-01-30 {
// description "NBC changes to initial revision";
// ysv:version 0.2.0;
// rev:non-backwards-compatible; // optional
// // (theoretically no
// // 'previous released version')
// }
// revision 2017-01-26 {
// description "Initial module version";
// ysv:version 0.1.0;
// }
//YANG module definition starts here
container example {
description
"This is an example container for the
example-versioned-module.";
leaf qux {
type string;
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description
"The qux instance of the device.";
}
leaf foo {
type string;
description
"The foo instance of the device.";
}
leaf bar {
type uint32;
description
"The magnitude of the foo. This leaf was
renamed from 'baz'.";
}
leaf wibble {
type boolean;
description
"Does it wibble (true) or wobble (false)?";
}
}
}
4.6.2. Example of Package Using YANG Semver
Below is an example YANG package that uses the YANG Semver version
identifier based on the rules defined in this document. Note: '\'
line wrapping per [RFC8792].
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{
"ietf-yang-instance-data:instance-data-set": {
"name": "example-yang-pkg",
"content-schema": {
"module": "ietf-yang-packages@2022-03-04"
},
"timestamp": "2022-12-06T17:00:38Z",
"description": ["Example of a Package \
using YANG Semver"],
"content-data": {
"ietf-yang-packages:packages": {
"package": [
{
"name": "example-yang-pkg",
"version": "1.3.1",
...
}
]
}
}
}
}
Figure 2
5. Import Module by YANG Semantic Version
[I-D.ietf-netmod-yang-module-versioning] defines the rev:recommended-
min-date extension that allows for the imported revision to be
selected based on any revision that matches -- or is later -- than
the specified revision date in the import. This section defines a
similar extension for controlling import by YANG semantic version, as
well as the rules for how imports are resolved.
5.1. The recommended-min-version Extension
The ietf-yang-semver module defines a "recommended-min-version"
extension -- a substatement to the "import" statement -- that takes
the numeric version triplet (i.e., X.Y.Z) of the YANG Semver as its
argument and specifies that the minimum version of the associated
module being imported SHOULD be greater than or equal to the
specified value. The specific conditions for determining if a
module's version is greater than or equal is defined in Section 5.2
below. At most one instance of recommended-min-version MAY be used.
Removing, adding or changing the recommended-min-version statement is
considered a backwards compatible change. An example use is:
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import example-module {
ysv:recommended-min-version 3.0.0;
}
5.2. Import by YANG Semantic Version Rules
When evaluating target module to import, only the numeric triplet of
MAJOR.MINOR.PATCH is considered. The "_compatible" and
"_non_compatible" modifiers as well as any metadata are ignored. A
module to be imported is considered as meeting the recommended
minimum version criteria if it meets one of the following conditions:
1. Has the exact same MAJOR, MINOR, PATCH as in the recommended-min-
version value.
2. Has the same MAJOR and MINOR version numbers and a greater PATCH
number.
3. Has the same MAJOR version number and greater MINOR number. In
this case the PATCH number is ignored.
4. Has a greater MAJOR version number. In this case MINOR and PATCH
numbers are ignored.
If the recommended-min-version is specified as 3.1.0, the following
examples would satisfy that recommended-min-version:
3.1.0 (by condition 1 above)
3.1.1 (by condition 2 above)
3.2.0 (by condition 3 above)
4.1.2 (by condition 4 above)
3.1.1_compatible (by condition 2 above, noting that modifiers are
ignored)
3.1.2_non_compatible (by condition 2 above, noting that modifiers
are ignored)
3.3.0-00 (by condition 3 above, noting that the pre-release
metadata is ignored)
If a compiler that supports the recommended-min-version extension
cannot locate a module with a version that is viable according to the
conditions above, that YANG compiler should emit a warning, and then
continue to resolve the import based on established [RFC7950] rules.
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6. Guidelines for Using YANG Semver During Module Development
This section and the IETF-specific sub-section below provide YANG
Semver-specific guidelines to consider when developing new YANG
modules. As such this section updates Section 4.8 of
[I-D.ietf-netmod-rfc8407bis].
All modules and submodules being developed or updated that use the
YANG Semver versioning scheme MUST have unique YANG Semver version
identifiers throughout their lifecycle.
Development of a new YANG module or submodule outside of the IETF
that uses the YANG Semver versioning scheme SHOULD begin with a 0 for
the MAJOR version component. This allows the module or submodule to
disregard strict SemVer rules with respect to non-backwards-
compatible changes during its initial development. However, module
or submodule developers MAY choose to use the SemVer pre-release
syntax instead with a 1 for the MAJOR version number. For example,
an initial module or submodule version might be either 0.1.0 or
1.0.0-alpha.1. If the authors choose to use the 0 MAJOR version
number scheme, they MAY switch to the pre-release scheme with a MAJOR
version number of 1 when the module or submodule is nearing initial
release (e.g., a module's or submodule's version may transition from
0.3.0 to 1.0.0-beta.1 to indicate it is more mature and ready for
testing).
When using pre-release notation, the pre-release metadata MUST adhere
to [SemVer] syntax. The following are examples of valid pre-release
versions:
1.0.0-alpha.1
1.0.0-alpha.3
1.0.0-beta.42
1.0.0-202007.rc.1
1.0.0-20250106
1.0.0-03
When updating an existing module or submodule using the YANG Semver
versioning scheme, the intended target semantic version can be used
along with pre-release notation. For example, if a released module
or submodule which has a current version of 1.0.0 is being modified
with the intent to make non-backwards-compatible changes, the first
development MAJOR version component should be 2 with some pre-release
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notation such as -alpha.1, making the version 2.0.0-alpha.1. It may
be prudent to include the year or year and month development began
(e.g., 2.0.0-201907-alpha.1) in order to guarantee uniqueness. As a
module or submodule undergoes development, it is possible that the
original intent changes. For example, a 1.0.0 version of a module or
submodule that was destined to become 2.0.0 after a development cycle
may have had a scope change such that the final version has no non-
backwards-compatible changes and becomes 1.1.0 instead. This change
is acceptable to make during the development phase so long as pre-
release notation is present in both versions (e.g., 2.0.0-alpha.3
becomes 1.1.0-alpha.4). However, on the next development cycle
(after 1.1.0 is released), if again the new target release is 2.0.0,
new pre-release components must be used such that every version for a
given module or submodule is unique throughout its entire lifecycle
(e.g., the first pre-release version might be 2.0.0-202005-alpha.1 if
keeping the same year and month notation mentioned above).
Module and submodule developers SHOULD maintain only one revision
statement in a pre-released module or submodule that reflects its
latest revision.
6.1. YANG Semver in IETF Modules
All published IETF modules and submodules MUST use YANG semantic
versions in their revisions. This is an update to the guidance
provided in Section 4.8 of [I-D.ietf-netmod-rfc8407bis].
6.1.1. YANG Semver in New IETF Modules
Development of a new module or submodule (i.e., when there is no
existing module of the same name) within the IETF MUST begin by using
0 as the MAJOR version component. If the Internet Draft containing
the module or submodule is an adopted document, pre-release metadata
MUST NOT be used. Instead, the Y.Z (i.e., MINOR.PATCH) version
components MUST be incremented with new revisions in order to
maintain version uniqueness.
6.1.2. YANG Semver when updating IETF Modules
When revising an existing IETF module or submodule, the version MUST
use the target (i.e., intended) MAJOR and MINOR version components
with a 0 PATCH version number. If the intended RFC release will be
non-backwards-compatible with the current RFC release, the MINOR
version number MUST be 0.
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6.1.2.1. Guidelines for IETF Modules Previously Published without YANG
Semvers
For IETF YANG modules and submodules that have already been
published, versions MUST be retroactively applied to all existing
revisions when the next new revision is created, starting at version
"1.0.0" for the initial published revision, and then incrementing
according to the YANG Semver version rules specified in Section 4.5.
For example, if a module or submodule started out in the pre-NMDA
([RFC8342] ) world, and then had NMDA support added without removing
any legacy "state" branches -- and you are looking to add additional
new features -- a sensible choice for the target YANG Semver would be
1.2.0 (since 1.0.0 would have been the initial, pre-NMDA release, and
1.1.0 would have been the NMDA revision).
6.1.3. YANG Semver when there are multiple parallel competing IETF
drafts
Whether a new IETF module is being defined, or a previously published
IETF module is being updated, special considerations are required
when multiple parallel competing drafts are in progress for a new
module or a module update.
The following recommendations apply to the 2nd, 3rd, etc. parallel
drafts that develop a module or submodule with the same name. The
first draft published can simply use the guidelines above without any
extra metadata described below. The YANG Semver in subsequent drafts
SHOULD include the full document name as a pre-release version
identifier, including the current document revision. For example, if
a module or submodule which is currently released at version 1.0.0 is
being revised to include non-backwards-compatible changes in draft-
user-netmod-foo, its development versions SHOULD include 2.0.0-draft-
user-netmod-foo followed by the document's revision (e.g., 2.0.0-
draft-user-netmod-foo-02). This will ensure each pre-release version
is unique across the lifecycle of the module or submodule. When
using the 0 MAJOR version for initial module or submodule development
in an individual Internet Draft (where MINOR and PATCH can change),
appending the draft name as a pre-release component helps to ensure
uniqueness when there are perhaps multiple, parallel efforts creating
the same module or submodule.
Other approaches are also possible to ensure uniqueness of YANG
Semver identifiers across all parallel competing modules and
revisions before IETF adoption including:
1. Using unique module names (i.e., module names with unique
prefixes such as the author's name, e.g. johnsmith-
interfaces.yang), or
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2. Using unique strings within the YANG Semver pre-release metadata
(e.g. 2.0.0-johnsmith-02).
Once an Internet Draft containing the module or submodule is adopted
as an IETF document, the need for pre-release metadata changes. For
new modules and submodules, the pre-release metadata MUST NOT be
used. Instead, the Y.Z (i.e., MINOR.PATCH) version components are
incremented as desired while leaving the X (i.e., MAJOR) component at
0. For module or submodule revisions, only the revision of the
Internet Draft is required. For example, if the module ietf-foo.yang
is being revised by draft-ietf-netmod-rfcABCDbis to include
backwards-compatible changes, its versions would be 1.1.0-01,
1.1.0-02, etc. as the draft progresses.
Some draft revisions may not include an update to the YANG modules or
submodules contained in the draft. In that case, those modules or
submodules that are not updated do not require a change to their
versions. Updates to the YANG Semver version MUST only be done when
the revision of the module changes.
See Appendix A for a detailed example of IETF pre-release versions.
7. Updates to ietf-yang-library
This document updates YANG 1.1 [RFC7950] and YANG library [RFC8525]
to clarify how ambiguous module imports are resolved. It also
defines the YANG module, ietf-yang-library-semver, that augments YANG
library [RFC8525] with a version leaf for modules and submodules.
7.1. YANG library versioning augmentations
The "ietf-yang-library-semver" YANG module has the following
structure (using the notation defined in [RFC8340]):
module: ietf-yang-library-semver
augment /yanglib:yang-library/yanglib:module-set/yanglib:module:
+--ro version? ysv:version
augment /yanglib:yang-library/yanglib:module-set/yanglib:module
/yanglib:submodule:
+--ro version? ysv:version
augment /yanglib:yang-library/yanglib:module-set
/yanglib:import-only-module:
+--ro version? ysv:version
augment /yanglib:yang-library/yanglib:module-set
/yanglib:import-only-module/yanglib:submodule:
+--ro version? ysv:version
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Figure 3
7.1.1. Advertising version
The ietf-yang-library-semver YANG module augments the "module" and
"submodule" lists in ietf-yang-library with "version" leafs to
optionally declare the version identifier associated with each module
and submodule.
8. YANG Modules
This YANG module contains the typedef for the YANG semantic version
and the identity to signal its use.
<CODE BEGINS> file "ietf-yang-semver@2025-09-29.yang"
module ietf-yang-semver {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-yang-semver";
prefix ysv;
organization
"IETF NETMOD (Network Modeling) Working Group";
contact
"WG Web: <http://datatracker.ietf.org/wg/netmod/>
WG List: <mailto:netmod@ietf.org>
Author: Joe Clarke
<mailto:jclarke@cisco.com>
Author: Robert Wilton
<mailto:rwilton@cisco.com>
Author: Reshad Rahman
<mailto:reshad@yahoo.com>
Author: Balazs Lengyel
<mailto:balazs.lengyel@ericsson.com>
Author: Jason Sterne
<mailto:jason.sterne@nokia.com>
Author: Benoit Claise
<mailto:benoit@everything-ops.net>";
description
"This module provides type and grouping definitions for YANG
packages.
Copyright (c) 2025 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Revised BSD License
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set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.";
// RFC Ed.: update the date below with the date of RFC publication
// and remove this note.
// RFC Ed.: replace XXXX with actual RFC number and remove this
// note.
// RFC Ed. update the ysv:version to "1.0.0".
revision 2025-09-29 {
ysv:version "0.24.0";
description
"Initial revision";
reference
"RFC XXXX: YANG Semantic Versioning.";
}
/*
* Extensions
*/
extension version {
argument yang-semantic-version;
description
"The version extension is used to assign a version number
to a module or submodule revision.
The format of the version extension argument MUST conform
to the 'version' typedef defined in this module.
The statement MUST only be a substatement of the revision
statement. Zero or one version statements per parent
statement are allowed. No substatements for this extension
have been standardized.
Versions MUST be unique amongst all revisions of a
module or submodule.
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Adding, changing or removing a version is a
backwards-compatible change.";
reference
"RFC XXXX: YANG Semantic Versioning;
Section 4.2, YANG Semantic Version Extension";
}
extension recommended-min-version {
argument yang-semantic-version;
description
"Recommends the versions of the module that may be imported to
one that is greater than or equal to the specified version.
The format of the recommended-min-version extension argument
must be the MAJOR.MINOR.PATCH components from the
'version' typedef defined in this module (i.e., excluding
the '_compatible' and '_non_compatible' modifiers as
well as any metadata).
The statement MUST only be a substatement of the import
statement. Zero or one 'recommended-min-version'
statements per parent statement are allowed. No
substatements for this extension have been
standardized.
A module to be imported is considered as meeting the
recommended minimum version criteria if it meets one of
the following conditions:
* Has the exact same MAJOR, MINOR, PATCH as in the
recommended-min-version value.
* Has the same MAJOR and MINOR version numbers and a
greater PATCH number.
* Has the same MAJOR version number and greater MINOR number.
In this case the PATCH number is ignored.
* Has a greater MAJOR version number. In this case MINOR
and PATCH numbers are ignored.
Adding, removing or updating a 'recommended-min-version'
statement to an import is a backwards-compatible change.";
reference
"RFC XXXX: YANG Semantic Versioning; Section 5,
Import Module by Semantic Version";
}
/*
* Typedefs
*/
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typedef version {
type string {
length "5..128";
pattern '[0-9]+[.][0-9]+[.][0-9]+(_(non_)?compatible)?'
+ '(-[A-Za-z0-9.-]+[.-][0-9]+)?([+][A-Za-z0-9.-]+)?';
}
description
"Represents a YANG semantic version. The rules governing the
use of this version identifier are defined in the
reference for this typedef.";
reference
"RFC XXXX: YANG Semantic Versioning.";
}
}
<CODE ENDS>
This YANG module contains the augmentations to the ietf-yang-library
[RFC8525].
<CODE BEGINS> file "ietf-yang-library-semver@2025-09-29.yang"
module ietf-yang-library-semver {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-yang-library-semver";
prefix yl-semver;
import ietf-yang-semver {
prefix ysv;
reference
"XXXX: YANG Semantic Versioning";
}
import ietf-yang-library {
prefix yanglib;
reference
"RFC 8525: YANG Library";
}
organization
"IETF NETMOD (Network Modeling) Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/netmod/>
WG List: <mailto:netmod@ietf.org>
Author: Joe Clarke
<mailto:jclarke@cisco.com>
Author: Robert Wilton
<mailto:rwilton@cisco.com>
Author: Reshad Rahman
<mailto:reshad@yahoo.com>
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Author: Balazs Lengyel
<mailto:balazs.lengyel@ericsson.com>
Author: Jason Sterne
<mailto:jason.sterne@nokia.com>
Author: Benoit Claise
<mailto:benoit@everything-ops.net>";
description
"This module contains augmentations to YANG Library to add module
and submodule level version identifiers.
Copyright (c) 2025 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Revised BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.";
// RFC Ed.: update the date below with the date of RFC publication
// and remove this note.
// RFC Ed.: replace XXXX (including in the imports above) with
// actual RFC number and remove this note.
// RFC Ed.: please replace ysv:version with 1.0.0 and
// remove this note.
revision 2025-09-29 {
ysv:version "0.24.0";
description
"Initial revision";
reference
"RFC XXXX: YANG Semantic Versioning";
}
grouping module-version {
description
"Grouping for module version information.";
leaf version {
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type ysv:version;
description
"The version of the module or submodule.
The value MUST match the version value in the specific
revision of the module or submodule loaded in this
module-set.";
reference
"RFC XXXX: YANG Semantic Versioning;
Section 7.1.1, Advertising version";
}
}
// library 1.0 modules-state is not augmented with version
augment "/yanglib:yang-library/yanglib:module-set/yanglib:module" {
description
"Add a version to module information";
uses module-version;
}
augment "/yanglib:yang-library/yanglib:module-set/yanglib:module/"
+ "yanglib:submodule" {
description
"Add a version to submodule information";
uses module-version;
}
augment "/yanglib:yang-library/yanglib:module-set/"
+ "yanglib:import-only-module" {
description
"Add a version to module information";
uses module-version;
}
augment "/yanglib:yang-library/yanglib:module-set/"
+ "yanglib:import-only-module/yanglib:submodule" {
description
"Add a version to submodule information";
uses module-version;
}
}
<CODE ENDS>
9. Contributors
The following people made substantial contributions to this document:
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Bo Wu
lana.wubo@huawei.com
Jan Lindblad
jlindbla@cisco.com
Figure 4
10. Acknowledgments
This document grew out of the YANG module versioning design team that
started after IETF 101. The team consists of the following members
whom have worked on the YANG versioning project: Balazs Lengyel,
Benoit Claise, Bo Wu, Ebben Aries, Jan Lindblad, Jason Sterne, Joe
Clarke, Juergen Schoenwaelder, Mahesh Jethanandani, Michael
(Wangzitao), Per Andersson, Qin Wu, Reshad Rahman, Tom Hill, and Rob
Wilton.
The initial revision of this document was refactored and built upon
[I-D.clacla-netmod-yang-model-update]. We would like to thank Kevin
D'Souza for his initial work in this problem space.
Discussions on the use of SemVer for YANG versioning has been held
with authors of the OpenConfig YANG models based on their own
[openconfigsemver]. We would like to thank both Anees Shaikh and Rob
Shakir for their input into this problem space.
We would also like to thank Joseph Donahue from the SemVer.org
project for his input on SemVer use and overall document readability.
11. Security Considerations
This section is modeled after the template described in Section 3.7
of [I-D.ietf-netmod-rfc8407bis].
The "ietf-yang-semver" and "ietf-yang-library-semver" YANG modules
define data models that are designed to be accessed via YANG-based
management protocols, such as NETCONF [RFC6241] and RESTCONF
[RFC8040]. These YANG-based management protocols (1) have to use a
secure transport layer (e.g., SSH [RFC4252], TLS [RFC8446], and QUIC
[RFC9000]) and (2) have to use mutual authentication.
The Network Configuration Access Control Model (NACM) [RFC8341]
provides the means to restrict access for particular NETCONF or
RESTCONF users to a preconfigured subset of all available NETCONF or
RESTCONF protocol operations and content.
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The YANG modules define a set of identities, extensions, types, and
groupings. These nodes are intended to be reused by other YANG
modules. The module by itself does not expose any data nodes that
are writable, data nodes that contain read-only state, or RPCs. As
such, there are no additional security issues related to the YANG
module that need to be considered.
12. IANA Considerations
12.1. YANG Module Registrations
IANA is requested to register the following URIs in the "ns" registry
within the "IETF XML Registry" group [RFC3688]:
URI: urn:ietf:params:xml:ns:yang:ietf-yang-semver
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-yang-library-semver
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
This document requests IANA to register the following YANG modules in
the "YANG Module Names" registry [RFC6020] within the "YANG
Parameters" registry group.
The ietf-yang-semver module:
Name: ietf-yang-semver
XML Namespace: urn:ietf:params:xml:ns:yang:ietf-yang-semver
Prefix: ys
Maintained by IANA? N
Reference: [RFCXXXX]
The ietf-yang-library-semver module:
Name: ietf-yang-library-semver
XML Namespace: urn:ietf:params:xml:ns:yang:ietf-yang-library-
semver
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Prefix: yl-semver
Maintained by IANA? N
Reference: [RFCXXXX]
12.2. Guidance for YANG Semver in IANA maintained YANG modules and
submodules
Note for IANA (to be removed by the RFC editor): Please check that
the registries and IANA YANG modules and submodules are referenced in
the appropriate way.
IANA is responsible for maintaining and versioning all IANA (iana-)
YANG modules and submodules, e.g., iana-if-types.yang [IfTypeYang]
and iana-routing-types.yang [RoutingTypesYang].
In addition to following the rules specified in the IANA
Considerations section of [I-D.ietf-netmod-yang-module-versioning],
IANA maintained YANG modules and submodules MUST also include a YANG
Semver version identifier for all new revisions, as defined in
Section 4.
The YANG Semver version associated with the new revision MUST follow
the rules defined in Section 4.5.
Note: For IANA maintained YANG modules and submodules that have
already been published, versions MUST be retroactively applied to all
existing revisions when the next new revision is created, starting at
version "1.0.0" for the initial published revision, and then
incrementing according to the YANG Semver rules specified in
Section 4.5.
Most changes to IANA maintained YANG modules and submodules are
expected to be backwards-compatible changes and classified as MINOR
version changes. The PATCH version may be incremented instead when
only editorial changes are made, and the MAJOR version would be
incremented if non-backwards-compatible changes are made.
Because IANA versions YANG modules with a linear history, these
modules will not need to use the "_compatible" or "_non_compatible"
modifiers with the "Z_COMPAT" version element.
13. References
13.1. Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
and R. Wilton, "YANG Library", RFC 8525,
DOI 10.17487/RFC8525, March 2019,
<https://www.rfc-editor.org/info/rfc8525>.
[I-D.ietf-netmod-yang-module-versioning]
Wilton, R., Rahman, R., Lengyel, B., Clarke, J., and J.
Sterne, "Updated YANG Module Revision Handling", Work in
Progress, Internet-Draft, draft-ietf-netmod-yang-module-
versioning-13, 6 February 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
yang-module-versioning-13>.
[I-D.ietf-netmod-rfc8407bis]
Bierman, A., Boucadair, M., and Q. Wu, "Guidelines for
Authors and Reviewers of Documents Containing YANG Data
Models", Work in Progress, Internet-Draft, draft-ietf-
netmod-rfc8407bis-28, 5 June 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
rfc8407bis-28>.
13.2. Informative References
[I-D.clacla-netmod-yang-model-update]
Claise, B., Clarke, J., Lengyel, B., and K. D'Souza, "New
YANG Module Update Procedure", Work in Progress, Internet-
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Draft, draft-clacla-netmod-yang-model-update-06, 2 July
2018, <https://datatracker.ietf.org/doc/html/draft-clacla-
netmod-yang-model-update-06>.
[I-D.ietf-netmod-yang-packages]
Wilton, R., Rahman, R., Clarke, J., and J. Sterne, "YANG
Packages", Work in Progress, Internet-Draft, draft-ietf-
netmod-yang-packages-06, 7 July 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
yang-packages-06>.
[I-D.ietf-netmod-yang-schema-comparison]
Andersson, P. and R. Wilton, "YANG Schema Comparison",
Work in Progress, Internet-Draft, draft-ietf-netmod-yang-
schema-comparison-02, 14 March 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
yang-schema-comparison-02>.
[RFC4252] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
January 2006, <https://www.rfc-editor.org/info/rfc4252>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
<https://www.rfc-editor.org/info/rfc8342>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/info/rfc8341>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
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[RFC8792] Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
"Handling Long Lines in Content of Internet-Drafts and
RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
<https://www.rfc-editor.org/info/rfc8792>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/info/rfc9000>.
[openconfigsemver]
"Semantic Versioning for Openconfig Models",
<http://www.openconfig.net/docs/semver/>.
[SemVer] "Semantic Versioning 2.0.0 (text from June 19, 2020)",
<https://github.com/semver/semver/
blob/8b2e8eec394948632957639dfa99fc7ec6286911/semver.md>.
[IfTypeYang]
"iana-if-type YANG Module",
<https://www.iana.org/assignments/iana-if-type/iana-if-
type.xhtml>.
[RoutingTypesYang]
"iana-routing-types YANG Module",
<https://www.iana.org/assignments/iana-routing-types/iana-
routing-types.xhtml>.
Appendix A. Example IETF Module Development
Assume a new YANG module is being developed in the netmod working
group in the IETF. Initially, this module is being developed in an
individual Internet Draft, draft-jdoe-netmod-example-module. The
following represents the initial version tree (i.e., value of
ysv:version) of the module as it's being initially developed.
Version lineage for initial module development:
0.1.0-draft-jdoe-netmod-example-module-00
|
0.2.0-draft-jdoe-netmod-example-module-01
|
0.3.0-draft-jdoe-netmod-example-module-02
|
0.3.1-draft-jdoe-netmod-example-module-03
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At this point, development stabilizes, and the workgroup adopts the
draft. Thus, now the draft becomes draft-ietf-netmod-example-module.
The pre-release metadata is no longer required.
Continued version progression after adoption:
0.4.0
|
0.4.1
|
0.5.0
At this point, the draft is standardized and becomes RFC12345 and the
YANG module version becomes 1.0.0.
A time later, the module needs to be revised to add additional
capabilities. Development will be done in a backwards-compatible
way. Two new individual drafts are proposed to go about adding the
capabilities in different ways: draft-jdoe-netmod-exmod-enhancements
and draft-asmith-netmod-exmod-changes. These are initially developed
in parallel with the following versions.
Parallel development for next module revision (track 1):
1.1.0-draft-jdoe-netmod-exmod-enhancements-00
|
1.1.0-draft-jdoe-netmod-exmod-enhancements-01
In parallel with (track 2):
1.1.0-draft-asmith-netmod-exmod-changes-00
|
1.1.0-draft-asmith-netmod-exmod-changes-01
At this point, the WG decides to merge some aspects of both and adopt
the work in asmith's draft as draft-ietf-netmod-exmod-changes. Since
the draft is now an adopted IETF document, the pre-release metadata
changes to simply include the adopted draft's revision. A single
version progression continues.
1.1.0-00
|
1.1.0-01
|
1.1.0-02
|
1.1.0-03
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The draft is standardized, and the new module version becomes 1.1.0.
Appendix B. Examples of _COMPAT Modifier Use
The following scenarios illustrate some situations where the _COMPAT
modifier (i.e., _compatible and _non_compatible) might be used in the
YANG Semver of a YANG module. While module development is considered
here, this is appliacable to any YANG artifact.
In the scenarios below, the X axis represents relative time (date &
time) that a module is being published. Module versions to the right
are more recent than module versions to the left. In scenario 1, for
example, the time ordered publishing of module versions is: 2.0.0,
2.1.0, 3.0.0, A, B.
It is also useful to consider the leftmost sequence (diagonal column)
of versions (going mostly downwards and slightly right) as the "main
branch" in a software development branching scheme, and the sequence
of versions moving rightwards (rows) as bug fixes in released
branches (i.e., maintenance releases in a single major release
stream).
These scenarios are generally more applicable for vendor modules
(which require modifications that are not at the head of the main
branch) and not expected to occur much in modules published by
standard bodies (which tend to be linear and only update the head of
the single branch).
2.0.0-----A
\
\
2.1.0------B
\
\
3.0.0
Figure 5: Scenario 1
For each revision A and B, the following are possible YANG Semver
versions when the revision is backwards comptible (BC) or non
backwards compatible (NBC):
Revision A (BC): 2.0.1_compatible
Revision A (NBC): 2.0.1_non_compatible
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2.2.0 is not allowed for A (see Section 4.4.3), and 4.0.0 is not
recommended (likely to cause confusion since it does not have 3.0.0
as an ancestor).
2.0.0
\
\
2.1.0----------N
\
\
2.2.0-----------P
\
\
2.2.1-------------Q
Figure 6: Scenario 2
For each revision N, P and Q, the following are possible YANG Semver
versions when the revision is backwards comptible (BC) or non
backwards compatible (NBC):
Revision N (BC): 2.1.1_compatible
Revision N (NBC): 2.1.1_non_compatible
Revision P: This is a situation that illustrates the limits of
branching in YANG Semver. It is not recommended to create any new BC
or NBC version off of 2.2.0. One approach to avoid this situation is
to avoid only incrementing the PATCH digit in the main branch (i.e.,
increment at least the MINOR digit).
For revision Q -- given that it is at the head of the branch -- the
following are possible YANG Semver versions when the revision is
backwards compatible (BC) or non backwards compatible (NBC):
Revision Q (BC): 2.3.0
Revision Q (NBC): 3.0.0
Authors' Addresses
Joe Clarke (editor)
Cisco Systems, Inc.
7200-12 Kit Creek Rd
Research Triangle Park, North Carolina
United States of America
Phone: +1-919-392-2867
Email: jclarke@cisco.com
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Robert Wilton (editor)
Cisco Systems, Inc.
Email: rwilton@cisco.com
Reshad Rahman
Equinix
Email: reshad@yahoo.com
Balazs Lengyel
Ericsson
1117 Budapest
Magyar Tudosok Korutja
Hungary
Phone: +36-70-330-7909
Email: balazs.lengyel@ericsson.com
Jason Sterne
Nokia
Email: jason.sterne@nokia.com
Benoit Claise
Everything OPS
Email: benoit@everything-ops.net
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