MOQ

Media over QUIC (MOQ) Working Group Interim Meeting Date: March 30, 2026

Summary

The MOQ working group held a virtual interim meeting to discuss the implementation of server-side Adaptive Bitrate (ABR) over MoQ, establish a roadmap for the stabilization of draft-ietf-moq-transport, and resolve several outstanding technical issues and pull requests. Key outcomes included a timeline targeting Working Group Last Call (WGLC) for MoQ Transport by August 2026 and consensus on several protocol mechanisms including fetch timeouts, redirected requests, and reserved namespaces for session-level diagnostics.

Key Discussion Points

1. Server-Side ABR Demo on MoQ

Presenter: Tongyu Dai Slides: Server Side ABR Demo on MoQ

Tongyu Dai presented an implementation of server-side ABR using draft-ietf-moq-transport and draft-ietf-moq-cmsf.

Implementation Details: The relay integrates the ABR algorithm. Currently, the relay parses the catalog to understand available bitrates, though Tongyu Dai noted a need for a more standardized way for relays to build this context.
Mechanism: Uses PUBLISH and PUBLISH_OK messages to signal track switches.
Observations:
- A significant challenge is the delay in buffer recovery after a downswitch because high-bitrate data already in flight continues to congest the network. Tongyu Dai suggested that MoQ needs a way to cancel ongoing object downloads effectively.
- Bandwidth estimation using QUIC CWND and RTT is fluctuating for small objects, requiring smoothing.
Discussion: Mike English inquired about the applicability of ABR to FETCH vs. SUBSCRIBE. Tongyu Dai noted that while FETCH is used for SEEK operations, it complicates server-side ABR because FETCH usually specifies a single track, making parallel ABR logic complex.

2. MOQT Roadmap Proposal

Presenter: Alan Frindell Slides: MOQT Roadmap Proposal

Alan Frindell outlined a path to WGLC for draft-ietf-moq-transport.

Timeline: Target Draft 18 as the next interop target (May). Target WGLC for Draft 20 in mid-August 2026.
Major Topics: The next three virtual interims will be dedicated to:
1. Rewind
2. Filters
3. DTS (Delivery Time Stamp) and Switching
Process: Proponents of these features are expected to drive resolutions asynchronously. Alan Frindell emphasized that "done is a feature" and the editors aim to close five issues per week.
Hybrid Interims: Martin Duke and Suhas Nandakumar discussed the necessity of a fall hybrid interim. The group decided to evaluate the need for a September/October meeting at the conclusion of the London hybrid interim in June.

3. MOQT PRs and Issues

Presenter: Alan Frindell Slides: MOQT PRs & Issues 3.30

The group discussed several technical issues for draft-ietf-moq-transport:

Error Codes (Issue 1243): Ian Swett and Suhas Nandakumar agreed on using a single code point space for RESET_STREAM and STOP_SENDING across both bidirectional and unidirectional streams.
Redirects (Issue 1481 / PR 1534): This PR adds a Redirect error code and a REDIRECT message. It supports moving a client to a different server or track. Mo Zanaty questioned the need for a timeout. Suhas Nandakumar argued against a timeout for now, suggesting it adds unnecessary complexity for "make-before-break" scenarios.
SUBSCRIBE_NAMESPACE Overlaps (Issue 1494): Discussion focused on how to widen or narrow a namespace subscription.
- Decision: Instead of allowing overlaps, the group favored using Request Update to change the namespace prefix parameter.
Fill Timeout (PR 1496): Discussed whether the timeout in FETCH should be a per-request budget or an absolute timer.
- Decision: Consensus for "Budget B"—the timeout represents the total time a relay is permitted to spend on upstream fetches to satisfy the request.
Send Rate Parameter (Issue 1354): Proposed for pacing FETCH data.
- Decision: The group (including Ian Swett, Luke Curley, and Mo Zanaty) expressed skepticism about its utility and complexity. The issue will be parked or deferred to the Rewind proposal.
Reserved Session Namespaces (Issue 1507 / PR 1555): Proposed reserving namespaces starting with a dot (e.g., .session) for stack-level diagnostics (e.g., congestion control logs).
- Decision: Reserve all namespaces/tuple zeros starting with a dot (.). These are hop-by-hop and must not be forwarded by relays.

Decisions and Action Items

Decision: Use a single error code space for all stream resets in draft-ietf-moq-transport.
Decision: SUBSCRIBE_NAMESPACE will use Request Update for prefix modifications instead of allowing overlapping subscriptions.
Decision: FETCH Fill Timeout will be implemented as a time budget for upstream relay fetches.
Decision: Reserve the . (dot) prefix for internal session-level tracks; these are non-forwardable.
Action Item (Chairs): Finalize the order of the next three virtual interims (Rewind, Filters, DTS/Switching).
Action Item (Editors): Update draft-ietf-moq-transport to reflect the consensus on error codes, namespace updates, and reserved dot-namespaces.

Next Steps

Consensus call for draft-ietf-moq-transport version 17 ends April 7, 2026.
Virtual interims scheduled for April 13 and April 27 to address the major "Big Rocks" (Rewind/Filters/DTS).
Participants interested in VOD optimizations (Issue 1316) or Subscription Flow Control (Issue 869) are encouraged to drive these proposals, or they will be closed without action.

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