Hi all,
The weekly call group thought it would be good to provide an advance look at
Key Issues #2 and #3 before the IETF117 NETMOD meeting.
For now on the list let's continue the focus on K1 but we'll start in on K2 &
K3 (if there is time) at IETF117.
Key Issue #2: Single v/s multiple revision label schemes
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Recap of revision-label-scheme:
* Extension defined in YANG module versioning document.
* Takes a mandatory parameter defining the scheme used, it is an identity
derived from revision-label-scheme-base
* Extension MUST be used if there is a revision label statement in the
(sub)module
* The YANG Semver document defines the scheme yang-semver
(note - the current YANG revision date is not considered a revision label /
label scheme)
* Example:
rev:revision-label-scheme "yangver:yang-semver";
Pros of revision-label-scheme:
* YANG Semver deemed too restrictive by some
* This provides flexibility to e.g. have vendor specific schemes which
allow for infinite branching where the versions have no semantic meaning
* Consistent framework for adding other schemes
Cons of revision-label-scheme
* Flexibility comes with cost of added complexity, e.g. what if a module
changes from scheme A to scheme B
* YANG Semver is sufficient for IETF and many vendors
* If some entity wants their own scheme they could just do it using their
own separate extension (outside of any "framework")
Impact of removing revision-label-scheme
* We would rename revision-label e.g. to yangsemver-label
* If a vendor wants a new versioning scheme, a proprietary extension would
need to be added by that vendor (including augmentations of yang library,
packages, etc)
* The current IETF documents would be simpler
* Cost/effort to make the changes to the documents
Key Issue #3: Why do we need YANG Semver (vs. SemVer 2.0.0)?
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SemVer 2.0.0:
* Linear (no branching)
* Simpler in construction
* Major
* Minor
* Patch
* 1.0.0, 1.0.1, 1.1.0, 2.0.0, ...
* If a new feature is needed in 1.0.1, a 1.2.0 would need to be minted
that incorporates the features of 1.1.0
* Widely liked by the industry, but only works well when updating at the
head (fine for open source, not acceptable for operators)
YANG Semver:
* Support for limited branching (maintenance of released code)
* Supports SemVer 2.0.0 rules
* MAJOR.MINOR.PATCH_MODIFIER
* _compatible
* _non_compatible
Example:
1.0.0
|
1.0.1 -- 1.0.2_non_compatible
|
1.1.0
|
2.0.0
A feature (or an NBC change can be backported)
Why YANG Semver:
* Given that module versioning allows branching, the labeling scheme must
also support branching
* YANG Semver is a compromise between power and simplicity
* Encourage "mostly" single track development with modifiers the
exception
* Retains support for some updates to older versions
* Sufficient for SDOs and vendors
* Industry is familiar with Semver - tried to stay close to it
Jason (he/him)
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