Session Date/Time: 17 Apr 2024 14:00

CBOR

Summary

The CBOR working group held an interim meeting to review the status of numerous documents and discuss ongoing technical issues. Key updates included progress on documents nearing publication, significant discussion on clarifications and implementation strategies for the "more-control" CDDL draft, and an experiment with application-oriented literals for placeholder code points. The group decided to initiate a working group adoption call for the "cbor-numbers" draft and acknowledged the need for external Yang expertise for upcoming Yang CBOR work.

Key Discussion Points

Document Status Overview: Casten gave a comprehensive update on over 20 documents, noting specific progress and pending actions.
RFC Editor Queue: The companion document to the CBOR Time Tag (RFC 9557) has completed its RFC 48 process and is awaiting publication, which is expected to facilitate the movement of the C-time tag document.
WG Last Call Documents: The edn, literals, and update-8610-grammar documents have completed their working group last call comments and are ready to be handed off to the IESG. Ari indicated he would finish the shepherd write-ups for edn and CDDL.
More Control Document:
- Deterministic CBOR: The previous feedback to remove control operators for deterministic CBOR from this document and move them to a CDDL draft has been incorporated (D4).
- Strictness Requirements: An experiment by Lawrence highlighted the need for more detailed definitions of strictness, particularly concerning unused bits in Base64 (RFC 4648). The proposed approach is strict validation where unused bits must be zero, with explicit allowances for sloppiness only where specifications mandate it. A PR is expected soon.
- do-join Operator: This powerful mechanism poses implementation challenges for validation (splitting a joined string back into its components). The current text is insufficient. Casten is exploring two implementation strategies:
  1. Scanning for constant markers (e.g., delimiters).
  2. Building parsing regular expressions from markers and variable elements. Casten favors the regex approach for potential simplicity.
Modules Document: Work is needed, particularly on handling sockets. Brendan raised further concerns that require discussion. A simple, implementable solution for sockets is sought.
Application-Oriented Literals (draft-ietf-cbor-numbers):
- This draft addresses the problem of using placeholder code points in examples, which can lead to number squatting. It proposes using an application-oriented literals mechanism.
- Marco successfully experimented with this mechanism in draft-ietf-ace-oscar-gm-edmin. He found it preferable to use the new notation only for yet-to-be-registered code points, while indicating registered code points with comments, rather than a hybrid approach. He is applying this in another draft (Ace revoked token notification).
- The cbor-numbers document is designed so it does not need to be normatively referenced from an RFC, making its publication status less critical for its current use in internet drafts.
Other Documents: Brief mentions were made of Pack to Work (needs renewed attention), Notable Tags (slowly moving, serves as a stable reference), serialization discussion (postponed), DCBOR document (needs decision), and a new Tag 201 (requires architectural discussion on interaction with encoding/serialization).
Yang CBOR Documents:
- Yang Standin: The proof-of-concept for compact Yang representation is technically stable, but discussions are needed on convergence with other Yang representations and how next hops in the processing chain detect this functionality.
- Yang CBOR Metadata Annotations: Andy Beerman suggested supporting metadata annotations (RFC 7952). The proposed CBOR representation encapsulates the instance in a tag (e.g., tag 109), with the tag content being an array [metadata, original_instance], aiming to replicate the simplicity of XML annotations. This work is currently in a GitHub repository and not yet a formal draft.
- Working Group for Yang CBOR: There is a sentiment to do further Yang CBOR work in the CBOR WG, particularly for CBOR representation specifics, but acknowledging the need to involve the Netmod WG.
External Work:
- RFC 9542 (BCP 141): Recently published, it adds CBOR tags for MAC addresses and OUIs, updating RFC 7042. The notable-tags document will be updated to reference this.
- CoRE WG CIS Model: Ongoing work on a CBOR representation of the UI data model called CIS is technically stable, with test vectors underway. It will become visible to the CBOR WG during its working group last call.
Yang Expertise Poll: A quick poll revealed that only one participant present felt familiar enough with Yang to review Yang CBOR material, highlighting the significant need for external Yang expertise if this work is to proceed within the CBOR working group.

Decisions and Action Items

The edn, literals, and update-8610-grammar documents will be handed off to the IESG. Ari will complete the shepherd write-ups for edn and CDDL.
Casten will create PRs for the "more-control" document, addressing strictness requirements (unused bits) and providing guidance on do-join validation strategies. AJ will shepherd this document.
The chair will initiate a working group adoption call on the mailing list for the cbor-numbers document.
For the Yang CBOR metadata annotation work, Casten will proceed with submitting the draft (d-00) when technically sound and will announce it to the Netmod working group.
The working group recognizes the need to identify and engage Yang experts to review future Yang CBOR-related documents.

Next Steps

Casten will prioritize creating the PRs for the "more-control" document, particularly for strictness and do-join validation.
The chair will issue the working group adoption call for cbor-numbers.
Casten will continue work on the modules document, focusing on the socket issue and incorporating Brendan's concerns.
Upon submission, the yang-cbor-metadata draft will require review, with an emphasis on securing input from Yang experts. A "Yang CBOR roadmap wiki page" may be created to guide this work.
The notable-tags document will be updated to include references to RFC 9542.
The serialization discussion and the DCBOR document decisions will be revisited in a future meeting.
The next interim meeting is scheduled for four weeks from now.