Session Date/Time: 07 Oct 2025 15:00

SNAC

Summary

The SNAC Working Group held an interim meeting to discuss document updates, preparations for the upcoming IETF meeting in Montreal, and review pending pull requests. Key discussions included the timing of document publications, potential content for the Montreal session, a significant reorganization of state machines, and several technical clarifications regarding message naming, network partitioning, route lifetimes, and prefix delegation. The group also addressed the applicability of RFC 9416 to ULA prefix generation and proposed normative text for Net64 prefix handling based on sub-network capabilities.

Key Discussion Points

Meeting Schedule: The chair noted that the scheduled interim for the 14th could be canceled due to conflicts with a Thread Group meeting.
IETF Note Well: An attempt was made to display the IETF Note Well. Attendees were reminded of its importance and directed to ietf.org/about/note-well.
Document Publication Request: The chairs requested authors to publish an updated draft version this week to show working group activity on the mailing list. Jonathan indicated he could publish.
IETF Montreal Session Planning:
- The SNAC Simple portion of the Montreal meeting is expected to be minimal, focusing on document updates.
- Esko suggested a detailed discussion on SNAC Simple fallback solutions, particularly for scenarios involving multiple AILs.
- Chairs intend to gauge interest in extending the working group's scope beyond SNAC Simple, potentially into "SNAC Complex" topics like DNSSD service on infrastructure (which has energy in MATTER participants).
- The goal is for the next published draft to be a strong candidate for a Working Group Last Call.
State Machine Reorganization (Ted):
- Ted is actively reorganizing the document's state machines to improve clarity and correctness, describing it as a "big change" requiring serious review.
- The new structure aims to abstract common machinery and then apply it specifically to AIL and stub network contexts.
- Introduced new state machines: a general Router Advertisement Monitor (for discovery and listening) and a per-router Router Monitor (for tracking individual router information and suitability).
- The intention is to make the state machine descriptions sufficiently clear for implementers without being strictly normative.
Pull Request Reviews (Esko):
- "Sync Message Names": Updated terminology to align with RFC 4861 for Router Advertisements (e.g., "Periodic unsolicited multicast RA message," "min_router_advertisement_interval," "max_router_advertisement_interval"). The "RA beacon" term was removed.
- "Move Partitioning Discussion to Informative Appendix": The discussion of partitioning events in mesh networks was moved to an informative appendix due to its dependency on specific stub network technologies. This section also outlines expectations for automatic adaptation to network changes.
- "Rename Step Network Reachable Time": The constant name "stop network reachable time" was clarified to "stop network route lifetime" to better reflect its use in route lifetime values advertised by the SNAC router on the infrastructure link (set to 30 minutes maximum).
- "Prefix Delegation (PD) Updates":
  - Introduced min_pd_prefix_lifetime as the minimum acceptable lifetime for a delegated prefix to be usable as an OSNR prefix, addressing reboot scenarios.
  - Clarified that PD clients do not request specific lease intervals; rather, they receive and evaluate offers from the server, treating offers below the minimum preferred lifetime as unsuitable.
Open Issues Discussion:
- RFC 9416 and ULA Prefix Generation: Discussed whether RFC 9416 (for generating transient numbers) applies to ULA prefix generation within SNAC. Consensus was that SNAC references the existing ULA RFC, and it is not the SNAC WG's responsibility to update the ULA RFC to comply with RFC 9416.
- Net64 Prefixes and Stability: Explored the handling of Net64 prefixes, particularly the rules for deprecation or withdrawal when multiple are available or when infrastructure-configured prefixes appear. Esko proposed rules based on sub-network capabilities (e.g., if a sub-network cannot advertise priority, the SNAC router must withdraw its generated Net64 prefix if an infrastructure-configured one is present). Ted highlighted the importance of avoiding connection breakage when changing Net64 prefixes.

Decisions and Action Items

Decision: Jonathan will publish an updated draft version as soon as possible this week.
Decision: The four pull requests presented by Esko ("Sync Message Names," "Move Partitioning Discussion to Informative Appendix," "Rename Step Network Reachable Time," "Prefix Delegation Updates") will be merged. (Note: One PR had conflicts and will be merged post-meeting.)
Action Item: The chairs will send another reminder to the mailing list for content proposals for the IETF Montreal meeting.
Action Item: Ted will continue work on the state machine reorganization, and the updated text will require thorough review by the working group.
Action Item: Esko will create a pull request to incorporate the discussed rules for Net64 prefix handling based on sub-network technology capabilities.

Next Steps

Publishing of the updated SNAC Simple draft.
Review and feedback on the reorganized state machine description.
Preparation for the IETF Montreal meeting, including detailed discussion on SNAC Simple fallback solutions and a discussion on the future scope of the SNAC Working Group beyond SNAC Simple.
Consideration of a Working Group Last Call for SNAC Simple after the next draft publication.