**Session Date/Time:** 25 Jul 2024 20:00

# bier

## Summary

The BIER working group meeting in Vancouver covered several key topics including charter and milestone updates, a new proposal for Unmasked BIER (U-Beer) to improve scalability, and a discussion of Brownfield deployment options for BIER. The meeting concluded with a presentation on loop avoidance using Segment Routing (SR).

## Key Discussion Points

*   **Charter and Milestones:** The working group discussed removing dates from milestones to reflect the volunteer-driven nature of the IETF process. Accomplishments will be archived. The charter is being updated to reflect accomplishments and new objectives related to AI data centers and replication fabrics.
*   **U-Beer Proposal (Tony):** Tony presented a proposal for "Unmasked BIER" (U-Beer) to address scalability issues with large BFR-ID spaces. U-Beer involves using a sequence of smaller BFR-IDs and allows for replication and invalid BFR-IDs. It can be mixed with standard BIER and offers potential compression benefits. There are considerations around how to control replication points on the fabric and whether compression is worthwhile. There's interest for use cases such as Mixture of Experts (MoE) for AI traffic.
*   **Brownfield Deployment Options (Human):** Human presented an information draft outlining various Brownfield deployment options for BIER, including naked multi-topology, section 6.9 of the architecture spec (RFC 8279), skipping non-BFRs in calculations, using a controller, tethering, and penultimate hop popping (PHP). The discussion centered on including solutions for stitching multiple PIM/MLDP domains via BIER in the Brownfield draft, and election of replication points when the same PIM domain is hooked up to the BIER domain at multiple points.
*   **Loop Avoidance using SR (Yuan Jiangchew):** Yuan presented a draft proposing the use of Segment Routing (SR) to avoid micro-loops in BIER forwarding. The approach involves calculating backup paths using existing IGP fast re-route technology. Concerns were raised that the proposal might simply be re-purposing existing IGP techniques.

## Decisions and Action Items

*   **Milestones:** Remove dates from milestones.
*   **Charter:** Update the charter as discussed, reflecting current accomplishments and new objectives (AI data centers, replication fabrics). Chair to send updated charter to the list for review.
*   **Brownfield Draft:** The draft will be expanded to include solutions for stitching multiple PIM/MLDP domains to a BIER core. Human and Jeffrey will work together on the content.
*   **U-Beer:** Authors to add more text on the U-Beer draft, addressing use-cases and deployment scenarios.

## Next Steps

*   Chair will update and redistribute the draft charter for review on the mailing list.
*   Human and Jeffrey will collaborate on revising the Brownfield draft to include stitching PIM/MLDP scenarios.
*   Yuan will take feedback from meeting to the mailing list for the loop avoidance draft.
*   Tony to add additional text to U-Beer draft for further discussion.