MBONED

IETF 125 - Brisbane, Australia Chairs: Lenny Giuliano, Greg Shepherd In-room Delegate: Jeffrey Zhang

Summary

The MBONED working group met to discuss the status of active documents, new use cases for multicast in Large Language Model (LLM) synchronization, a proposal for dynamic internet multicast tunneling, and a report on real-world multicast deployment for professional sports streaming. Several documents are currently in Working Group Last Call (WGLC), and the chairs emphasized the need for community feedback to advance them.

Key Discussion Points

Working Group Status and Draft Updates

draft-ietf-mboned-multicast-yang-model: Currently in WGLC (ends Friday). The draft was updated following extensive off-list feedback. Chairs noted a lack of on-list responses from non-authors and stressed that consensus cannot be determined without broader participation.
draft-ietf-mboned-redundant-ingress-failover: In WGLC for a few more weeks. Updated recently after directorate reviews.
draft-ietf-mboned-non-source-routed-sr-mcast: Just entered WGLC. This is an informational document regarding deployment options in Segment Routing networks.
draft-ietf-mboned-multicast-security: No recent updates; authors were not present.
draft-ietf-mboned-dorms: Awaiting Security Directorate review. The request was recently reopened after previous attempts were unsuccessful.
Parking of Documents: The authors of draft-ietf-mboned-cbacc and draft-ietf-mboned-ambi suggested parking these documents due to a lack of current implementation interest or the drafts being overtaken by other technologies (e.g., Multicast extensions for QUIC).

Multicast for LLM Synchronization

Presentation: update-llmsyn-multicast Presenter: Sandy Zhang

Use Case: Delivering large-scale models (70GB to 1TB) from central repositories to distributed GPU clouds for real-time inference.
Challenges: High concurrency leads to I/O bottlenecks at storage points; "cold start" latency affects inference service availability.
Technical Analysis:
- PIM-SM and SR-P2MP are suitable for fixed destination sets.
- BIER provides a stateless, dynamic alternative for evolving sets of destination GPU clouds.
Discussion: The presenter is seeking the appropriate working group for this work (options include MBONED, BIER, PIM, or RTGWG).

Dynamic Internet Multicast Tunneling

Presentation: Dynamic Internet Multicast Tunneling Presenter: Lenny Giuliano

Problem: While Automatic Multicast Tunneling (AMT) is effective for the last mile, it lacks a standard mechanism for routers to dynamically discover which relay to use for specific sources in the "middle mile."
Proposal: Use a BGP Extended Community to encode the AMT relay IP address within the route advertisement for the multicast source.
Technical Benefits: Allows core routers to act as AMT gateways/relays dynamically, connecting "multicast islands" across a unicast-only internet without manual GRE tunnel configuration.
Feedback: Early feedback from IDR experts suggests that a new BGP attribute might be more appropriate than an extended community for internet-wide propagation. The authors will update the draft to reflect this.
WG Placement: The chairs believe MBONED is the correct home as it pertains to relay discovery, similar to RFC 8777 (Dryad).

Aircast's Internet Multicast Experience: Australian Open

Presentation: Aircast's Internet Multicast Experience for the Australian Open Presenter: Sanjay Mishra

Deployment: Aircast Live utilized AMT to stream live 1080p/30fps video from the Australian Open to global participants.
Performance: Achieved glass-to-glass latency of 500ms–900ms (Melbourne to Boston/India), significantly faster than traditional chunk-based streaming (which ranged from 18 seconds to 2 minutes).
Implementation Hurdles:
- Lack of external IP addresses at the venue required a complex stack: Wireguard -> GRE -> AMT.
- VLC 4.0 had issues with Variable Bitrate (VBR) over RTP, requiring a fallback to Constant Bitrate (CBR).
Next Steps: Focus on security/authentication between gateways and relays, multicast encryption for content protection, and adaptive bitrate support.

Decisions and Action Items

Decision: draft-ietf-mboned-cbacc and draft-ietf-mboned-ambi are officially parked due to lack of interest.
Action Item: Working Group members are urged to review and comment on draft-ietf-mboned-multicast-yang-model, draft-ietf-mboned-redundant-ingress-failover, and draft-ietf-mboned-non-source-routed-sr-mcast before their respective WGLC deadlines.

Next Steps

Lenny Giuliano and Jeffrey Zhang to update the Dynamic Internet Multicast Tunneling draft based on IDR feedback regarding BGP attributes vs. extended communities.
Sanjay Mishra and Craig (Aircast) to continue investigating multicast encryption and authentication mechanisms for future deployments.
The chairs will monitor the security directorate review for draft-ietf-mboned-dorms.

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