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Media over QUIC Transport (MOQT)

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draft-ietf-moq-transport-17 | 121 pages | Expires 2026-09-03

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Abstract

MOQT defines a media transport protocol operating over QUIC and WebTransport. It uses a publish-subscribe model where producers publish data that is consumed by multiple endpoints via subscription. The protocol treats relays as first-class citizens, enabling intermediate content distribution networks for high-scale, low-latency distribution.

Key Concepts

  • publish-subscribe: Core messaging pattern - PUBLISH, SUBSCRIBE, FETCH, REQUEST_OK/REQUEST_ERROR, PUBLISH_DONE
  • subgroups-and-objects: Data hierarchy: Track > Group > Subgroup > Object
  • relays: First-class relay support for CDN-style distribution
  • track-properties: Metadata attached to tracks and objects via Key-Value Pairs
  • joining-fetch: Mechanism to fetch historical data when joining a live session
  • qmux: TCP fallback via QUIC multiplexing over TLS+TCP
  • URI Scheme: moqt:// URI scheme with fragment identifier support (PR #1571)

Recent Changes (draft-17)

Draft-17 was published 2026-03-02 with significant changes from draft-16:

  • Unidirectional control streams for 0-RTT subscribe capability
  • SUBSCRIBE_NAMESPACE split into two messages: SUBSCRIBE_NAMESPACE (namespace info) and SUBSCRIBE_TRACKS (PUBLISH notifications)
  • Subscription filters moved to be a Param (PR #1590)
  • Track Properties added to REQUEST_OK (PR #1576)
  • Allow 7-byte varint and non-minimal encodings (PR #1595)
  • Editorial: consistent use of “MOQT” for protocol references (PR #1597)
  • Editorial: use “message” instead of “frame” (PR #1587)

Active Issues (as of 2026-04-15)

Design Issues

  • #1603 - What is the use case for required-request-id (questions if field is needed beyond REQUEST_UPDATE/FETCH)
  • #1602 - Joining Fetch should be on the SUBSCRIBE/PUBLISH stream
  • #1598 - Why PUBLISH_OK not REQUEST_OK? (Needs PR, Editorial & Minor Design)
  • #1585 - Exclude your own tracks from SUBSCRIBE_NAMESPACE
  • #1582 - Caching and propagation of REQUEST_ERRORs (Design)
  • #1581 - Request cancellation should be able to specify an error code
  • #1578 - Bikeshed: Largest Object should be Next Object
  • #1550 - Properties Type collision between moq-16 and loc-01
  • #1405 - Single Object Subgroups don’t need a Subgroup ID (likely closing — no WG appetite for change)

Open PRs

  • PR #1605 - Split DELIVERY_TIMEOUT into two types of timeout (Victor Vasiliev, Apr 14)
  • PR #1604 - Joining FETCH with subscription (implements #1602)
  • PR #1596 - Exclude your own tracks from SUBSCRIBE_NAMESPACE
  • PR #1593 - RFC: Allow framing single Objects without Subgroup ID
  • PR #1591 - RFC: Add flow control for Subscriptions
  • PR #1588 - Add internationalization statement for moqt URI scheme
  • PR #1586 - Make Object ID and Group ID delta encoded in Fetch responses
  • PR #1562 - RFC: Add Session-Level Tracks reserved namespace

Recently Merged

  • PR #1599 - Move normative text on Track Alias
  • PR #1597 - Consistently use MOQT for protocol references
  • PR #1595 - Allow 7-byte varint and non-minimal encodings
  • PR #1590 - Subscription filters are a Param
  • PR #1583 - Allow publisher to reopen subgroup after REQUEST_UPDATE fwd 0→1
  • PR #1577 - Clarify Joining Fetch ordering with Forward State transitions
  • PR #1576 - Add Track Properties to REQUEST_OK
  • PR #1540 - Allow coalescing REQUEST_UPDATE processing

ALPN Negotiation

Draft-17 uses ALPN strings for version negotiation:

  • qmux-00.moqt-17 - QUIC multiplexed, draft-17
  • qmux-00.moqt-16 - QUIC multiplexed, draft-16
  • qmux-00 with no suffix implies draft-14 (legacy)

Related Drafts

Mailing List

Consensus Call on draft-17 (March 2026)

martin-duke initiated a consensus call on the mailing list (2026-03-24) for draft-17 changes. The thread received responses through April 10, 2026.

7-Byte Varint Encoding Debate

Multi-week mailing list thread (March 19 - April 7) about the new varint format introduced in draft-17. The 7-byte encoding (6 leading ones) was initially marked invalid. Discussion among alan-frindell, martin-duke, suhas-nandakumar, Ian Swett, Mo Zanaty, and Christian Huitema led to PR #1595 allowing 7-byte varint and non-minimal encodings.

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