**Session Date/Time:** 23 Jul 2025 09:30

# bier

## Summary

The BIER working group meeting covered the status of existing drafts, a presentation on Halo Labels draft, and a presentation on the MOE multi-cost use case. A lively discussion ensued regarding the Halo Labels draft and its implications for interoperability, ultimately leading to a decision to adopt the draft and expand its scope. The MOE use case presentation sparked a discussion about the relevance of multicast in AI networks and potential deployment strategies.

## Key Discussion Points

*   **Halo Labels Draft:**
    *   Clarification of the draft's purpose in resolving inconsistencies in MPLS payload type identification within the BIER header.
    *   Discussion around the semantics of the protocol field and the distinction between global and context alphabets.
    *   Debate regarding the implementation requirements for BIER routers supporting upstream and downstream labels, with concerns about interoperability and vendor choices.
    *   Whether the draft should only address semantics, or attempt to enforce greater interoperability.
    *   The use of downstream and upstream assigned service labels
*   **MOE Multi-Cost Use Case:**
    *   Introduction of MOE (Mixture of Experts) architecture in large language models (LLMs) and its potential benefits for training and inference.
    *   Exploration of using multicast to reduce the pressure on source GPUs and alleviate latency/bandwidth issues in MOE deployments.
    *   Discussion about the data volume transferred to experts and the trend of increasing context, prompting questions about the scalability and relevance of multicast.
    *   Consideration of alternative approaches like broadcast and GMP, as well as the potential for leveraging switch-level adoption instead of NICs.
    *   The importance of reliability in AI networks and the need for multicast solutions to integrate with existing reliable transmission functions.
    *   Question of the charter scope of the BIER working group and whether the scope of the AI issues should be discussed in other IETF groups, or the IRTF

## Decisions and Action Items

*   **Halo Labels Draft:**
    *   Decision to adopt the Halo Labels draft as a working group item.
    *   Agreement to expand the scope of the draft to address interoperability concerns and define more specific behaviors for vendors implementing BIER with MPLS.
    *   Take the updated draft to the mailing list for further discussion and refinement.
*   **MOE Multi-Cost Use Case:**
    *   Authors to connect with other IETF and IRTF groups working on data center AI to gather more data and explore potential solutions.

## Next Steps

*   Authors to revise the Halo Labels draft based on the meeting discussions and submit it to the mailing list for further review and potential refinements.
*   Authors to investigate alternative solutions.
*   Working group to explore the potential for switch-level adoption of BIER in data centers.
*   Working group to consider how to balance solving AI multicast issues with the existing charter.