Session Date/Time: 22 Nov 2023 15:00

CORE

Summary

The CORE Working Group discussed the status of COVI and OSCAR-AD-HOC documents. A significant part of the meeting focused on the discoverability of CoAP URIs and interface types, leading to a proposal for an informative GitHub Wiki page. Updates to the HRE document were presented, including new CoAP options for CRIs and a discussion on handling scheme numbering in IANA registries and CoAP options. The group also noted an ongoing adoption call for a document.

Key Discussion Points

Document Status Updates:
- COVI: Remains in ISG processing with two discusses from older versions. Progress is pending AD action to clear these, with delays attributed to recent IETF discussions and upcoming holidays.
- OSCAR-AD-HOC: Expected to merge PRs and submit version 10 early next week, with the aim of being considered at the November 30th ISG meeting.
Discoverability of CoAP Interface and Resource Type URIs/URNs:
- Esco raised a question regarding the registration and discoverability of CoAP interfaces defined using URNs/URIs.
- Current IANA registry policy does not allow registering URNs/URIs as they are managed by the namespace owner (e.g., /.well-known/core-parameters).
- Concern: Without registration, it is difficult for practitioners to find an overview of all defined CoAP attributes like interface types or resource types.
- Discussion explored alternative methods for making this information discoverable, given IANA's reluctance to create new registries for informative purposes.
- A Wiki page on the CoRE GitHub organization was proposed as an informative resource to list organizations or specifications defining such CoAP attributes.
- It was suggested that IANA could be asked to add a note referencing this Wiki page in the existing CoAP Interface Type (if) and Resource Type (rt) registries.
HRE Document Updates (CRIs in CoAP):
- CRI Conversion Procedures: Carsten presented the need to add procedures for converting CRIs to CoAP options (e.g., Uri-Path, Uri-Query), analogous to sections 6.4 and 6.5 of RFC 7252 for URIs. This would include addressing the anomaly of a trailing slash after an authority.
- New CoAP Options for CRIs:
  - Proxy-CRI Option: A new CoAP option, analogous to Proxy-URI, was proposed. It would carry a CBOR-encoded CRI as opaque binary data. Semantically, it functions similarly to Proxy-URI, with the Proxy-CRI overriding Proxy-URI if both are received (though sending both in a request would be forbidden).
  - Proxy-Scheme-Number Option: An alternative to Proxy-Scheme (which uses text labels), this option would use a numeric scheme ID. This is relevant given the new IANA scheme registry.
    - A challenge was noted with CoAP's unsigned integer encoding for options, while CRIs use negative numbers for schemes (e.g., -1 for CoAP, -2 for CoAPS).
    - Two approaches were discussed:
      1. Map negative CRI scheme numbers to unsigned option values (e.g., -1 maps to 0, -2 maps to 1).
      2. Modify the IANA scheme registry itself to use unsigned numbers (0 for CoAP, 1 for CoAPS, etc.) and apply a negation (e.g., - (value + 1)) only when constructing a CRI. The latter was considered "easier to explain" and more palatable.
- Location URI with Different Schemes: Carsten raised a point about the current inability to specify a Location-URI with a different CoAP scheme (e.g., CoAP+TCP). If this functionality is added, a numeric option would be preferred over a text-based one, given the existence of the scheme registry.
- New Option Numbers: Discussion on appropriate option numbers for Proxy-CRI and Proxy-Scheme-Number, suggesting values in the 1-255 range for single-byte encoding, potentially by adding 200 to the existing Proxy-URI (35) and Proxy-Scheme (39) numbers for memorability.
Adoption Call: There is an ongoing adoption call for a document. Participants are encouraged to provide feedback or additional information on the mailing list. If no objections or further input are received, the draft will proceed to adoption, confirming previous in-room consensus.

Decisions and Action Items

Decision: An informative Wiki page will be established on the CoRE GitHub organization to list and describe CoAP interface and resource type URIs/URNs used by different organizations/specifications.
Decision: The IANA scheme registry for CRIs will be adjusted to store unsigned numbers, with the negative mapping applied when the scheme ID is used as the first data item in a CRI.
Decision: The HRE document will be updated to include new CoAP options (Proxy-CRI, Proxy-Scheme-Number) and procedures for converting CRIs to CoAP options.
Action Item: Esco to start preparing a list of CoAP URIs/interfaces to populate the new Wiki page.
Action Item: Carsten to update the HRE document's Pull Request with the following:
- Analogous text for CRI to CoAP option conversion (similar to RFC 7252 sections 6.4/6.5).
- The new Proxy-CRI and Proxy-Scheme-Number options, incorporating the agreed-upon approach for unsigned scheme registry values.
- Considerations for location URIs with different schemes.
Action Item: Working Group participants to review the adoption call for the current document and provide any relevant input on the mailing list.

Next Steps

The interim meeting scheduled in two weeks is likely to be cancelled unless critical and urgent issues arise.
Regular working group meetings are planned to resume in January.
Continue discussions on the mailing list regarding ongoing work and the adoption call.