Session Date/Time: 24 Jul 2023 20:00

netmod

Summary

The NETMOD working group met at IETF 117 in San Francisco. Key topics discussed included module versioning, extensions to the Access Control List (ACL) YANG model, the system configuration YANG model, and guidelines for authoring and reviewing YANG data models. The session focused on reaching consensus on allowing non-backwards compatible changes in YANG.

Key Discussion Points

Module Versioning:
- Discussion on allowing non-backwards compatible (NBC) changes in YANG.
- Three options were presented: updating RFC 7950 (Yang 1.1) to allow NBC changes, creating a new version of YANG (Yang 1.2) to accommodate NBC changes, and strictly adhering to current RFC 7950 rules (no NBC changes).
- Concerns raised regarding the impact on existing tools and implementations if a new version of YANG is introduced.
- Arguments were made for and against allowing NBC changes in YANG and for the various versioning options.
ACL YANG Model Extensions:
- Updates and extensions to the existing ACL YANG model RFC to address identified gaps and use cases, including support for EVPN and MPLS headers.
- Discussion on which actions to include in the ACL model (e.g., remarking packets, assigning packets to a VRF, logging, redirecting).
- The group will need to review the model and the proposed extensions with the MPLS working group to get input.
System Configuration YANG Model:
- Discussion focused on the handling of configuration data, clarification of reference meaning, and the ongoing debate about offline validation of the running datastore.
- The key question is whether running on its own always expects to be valid or if it is implicitly valid, based on a merge of running plus system into the intended.
- Different opinions regarding the copying of referenced system nodes into running.
Guidelines for Authoring/Reviewing YANG Models:
- Updates to the YANG guideline document focused on maintenance and the use of security templates.
- Discussion on whether the security template is too broad with some feeling that it captures too many components of a model.
- It was also recommended to file an errata against the existing RFC to add the extra tags that solve the problem in the immediate term.

Decisions and Action Items

Decision: The working group reached a consensus to move towards supporting NBC changes in YANG. This will be confirmed on the list.
Action Item: The chairs will discuss internally regarding the versioning approach that was presented.
Action Item: Dave will draft an acknowledgment of the liaison from the BBF to send back for comment on the mailing list.
Action Item: Authors of the ACL YANG model extensions will update the document based on the discussion and consult with the MPLS working group regarding the MPLS header matching.
Action Item: Authors of the YANG guideline will add the required updates to the security template

Next Steps

The NETMOD working group will hold an interim meeting to further discuss versioning.
The working group will follow up with action items.
Discussion will continue on the mailing list.