Session Date/Time: 24 Sep 2025 14:00

CORE

Summary

This interim meeting focused on the status of three key documents: the CRI (Constraint Resource Identifiers) document, the SIDPEN (YANG Schema Item Description Private Enterprise Number) document, and the recently adopted CoAP Abbreviated Path Options document. The discussion also included a proposed optimization for Constrained BRski discovery, which explored the use of unspecified IPv6 addresses in CoAP link-format. Key decisions included advancing the CRI document to ISG evaluation, preparing the SIDPEN document for Working Group Last Call, and formally adopting the CoAP Abbreviated Path Options document.

Key Discussion Points

CRI (Constraint Resource Identifiers) Document Status
- The document has passed AD review and is currently awaiting ISG evaluation.
- Dash-24 addressed most AD review comments.
- Two remaining issues are being addressed via pull requests:
  - More examples: The document will point to the CORE WG wiki at wiki.ietf.org for additional examples and test vectors (PR 138). The wiki now has a page pointing to the GitHub source repo for href test vectors, providing a stable link for evolving content.
  - ToASCII processing for regname: Clarification that ToASCII processing for regname in the UI authority part is explicitly out of scope for the CRI document (PR 139). This aims to avoid requiring full Unicode tables on constrained devices and treats ToASCII as a UI concept, not a CRI concept.
- A sense of those present indicated satisfaction with the proposed resolutions for these issues.
SIDPEN (YANG Schema Item Description Private Enterprise Number) Document Status
- This is a Working Group document intended to provide a "zero-threshold" mechanism for third-party YANG models to obtain numeric Schema Item Identifiers (SIDs) using Private Enterprise Numbers (PENs).
- Current YANG-CBOR (RFC 9254) requires SIDs, with a formal mechanism for RFCs, but an easier method is needed for ad-hoc YANG models.
- Discussion from May highlighted concerns about ensuring that "zero effort" doesn't mean "zero responsibility," particularly regarding the availability of SID files.
- The author plans to add "implementer notes" or text to the document clarifying expectations for authors to make their SID allocations from PENs easily accessible. This is not a technical change but sets expectations.
Constrained BRski Discovery Method (Unspecified Address Discussion)
- Esko presented a proposal from the ANIMA WG related to Constrained BRski discovery using unsecured CoAP and link-local addresses.
- The current protocol for discovering a Joint Proxy involves a node sending a CoAP request for a specific resource type (brewski.jp) and receiving a link in response. The joining device then contacts the proxy using the source address of the response message, not necessarily the address specified in the returned link.
- Proposed optimization: To reduce overhead and bytes, it was suggested to use the unspecified IPv6 address [::] in the returned link, implying the client should use the sender's IP address.
- Concerns raised (Karsten):
  - The unspecified address [::] has a defined meaning (e.g., "self" or "any local address") and giving it a new, implicit meaning could cause backward compatibility issues and unexpected behavior (e.g., web browsers and OS kernels often resolve [::] to [::1] or a local host address).
  - Such usage could introduce security vulnerabilities (e.g., cross-protocol attacks) by leading clients to unintended local addresses.
  - The link-format relies on URI resolution (RFC 3986), which does not support this type of partial compression (retaining the server's host while specifying a different port).
- Alternative suggestions:
  - If the primary goal is to discover port numbers and protocol variations rather than a full link, consider defining a new, compact media type (e.g., application/brewski+cbor) for the discovery response. This would allow explicit encoding of necessary information (e.g., a CBOR array of port numbers and profiles) without misusing link-format semantics.
  - Advanced compression/deduplication could be considered with CORAL (Concise Object Representation for Application Links) in the future, though CORAL's serialization is still evolving.
- The general sense was that using [::] as a shorthand for "sender's address" in this context is problematic due to existing semantics and potential security implications. The alternative of a dedicated, compact media type for discovery responses should be explored further.
CoAP Short Paths Document Adoption
- The document, which was previously in "call for adoption," received positive feedback on the mailing list.
- Discussion around the document title: "short paths" is a misnomer, as the path itself is not shortened, but an abbreviated form is used. The option name used in the draft is Ebrev (for "abbreviation").

Decisions and Action Items

CRI Document:
- Decision: The Working Group is generally happy with the proposed resolutions in PR 138 and PR 139.
- Action Item: Karsten to signal the AD for ISG evaluation within the next 24-48 hours, assuming no further objections or comments are received. Individuals are encouraged to review PRs 138 and 139.
SIDPEN Document:
- Action Item: Author (Karsten) to submit a -02 draft including implementer notes/text to clarify expectations for SID file availability.
- Action Item: Initiate a Working Group Last Call for the SIDPEN document once the -02 draft is published.
- Action Item: Chairs will begin looking for a document shepherd.
Constrained BRski Discovery Method:
- Decision: The proposed use of [::] (unspecified IPv6 address) as a shorthand for the sender's address in link-format for discovery responses is deemed problematic due to existing URI semantics, potential for misinterpretation by clients, and security concerns.
- Action Item: Esko to consider alternative approaches, such as defining a new, compact CBOR-based media type for discovery responses that explicitly carries the necessary information (e.g., port numbers, protocol variations) without misusing link-format semantics.
CoAP Short Paths Document:
- Decision: The document is formally adopted as a Working Group document.
- Action Item: Karsten to update the document name to align with the option name Ebrev (e.g., "CoAP Abbreviated Path Options" or similar) upon submission as a Working Group document.

Next Steps

CRI document to proceed to ISG evaluation.
SIDPEN document to be revised with implementer notes and then enter Working Group Last Call.
Discussion on Constrained BRski discovery to continue, focusing on alternative compact media types for discovery results.
The newly adopted CoAP Abbreviated Path Options document will be revised for name alignment.