Summary: S4-260525 – Pseudo-CR on Annex for MOQT Session Setup and Media Delivery Models

Source: NTT | Spec: 3GPP TR 26.836 v0.1.1 | WI: FS_Q4RTC_MED | For: Agreement

Purpose

Contributes informative annex content to TR 26.836 to support evaluation of Media over QUIC Transport (MOQT) for RTC application scenarios, as part of the FS_Q4RTC_MED study item.

Changes Proposed

References section update: - Updates reference [18] (draft-ietf-moq-transport) from draft-16 to draft-17 / March 2026 version.

New Annex A (Informative): MOQT Session Setup and Media Delivery Models

• A.2 – MOQT Session: Describes the MOQT session structure over native QUIC or WebTransport, covering use of unidirectional control streams (SETUP, GOAWAY), bidirectional request streams (SUBSCRIBE, PUBLISH, FETCH, etc.), and datagrams/streams for object delivery. Covers session setup (SETUP message exchange) and termination (CONNECTION_CLOSE for native QUIC; CLOSE_WEBTRANSPORT_SESSION for WebTransport).

• A.3 – Media Delivery Models and Call Flows: Defines two models:

• E2E unidirectional delivery without Relay – direct publisher-to-subscriber flow including namespace discovery (SUBSCRIBE_NAMESPACE, PUBLISH_NAMESPACE, or out-of-band), catalog track subscription (subscriber- or publisher-initiated via SUBSCRIBE/PUBLISH messages), media track subscription, and subscription termination (STOP_SENDING or PUBLISH_DONE).

• Unidirectional delivery for multiple subscribers using Relay – referenced but call flow detail not included in this contribution.

• Call flows assume use of MOQT Streaming Format (MSF) (draft-ietf-moq-msf) for catalog-based track discovery.

Notes

• Contains minor editorial errors in the draft text (e.g., "PUPBLISH_OK", "publisehr", inconsistent step numbering) that would need correction before agreement.
• Relay model (A.3.3) is referenced but not yet populated in this contribution.

Summary: S4-260526 – Pseudo-CR on MOQT Call Flow for Multi-Subscriber Using Relay

Source: NTT | Spec: 3GPP TR 26.836 v0.1.1 | Meeting: SA4 #135-bis-e

What is Proposed

• Adds a new clause A.3.3 to TR 26.836 providing an example call flow and model diagram for MOQT-based media delivery to multiple subscribers via a Relay, as part of the FS_Q4RTC_MED study item.

Key Technical Details

• Topology: Original Publisher → Relay → Subscriber_1 and Subscriber_2; Relay maintains separate MOQT sessions with each endpoint.
• Relay caching: The Relay can cache object data for both catalog tracks and media tracks, enabling it to serve subsequent subscribers without re-fetching from the Publisher.
• Subscription reuse: When Subscriber_2 requests a track already subscribed by Subscriber_1, the Relay reuses the existing upstream subscription to the Publisher (no duplicate SUBSCRIBE sent upstream).
• Catalog discovery: Each subscriber optionally sends a SUBSCRIBE for the Publisher's catalog track via the Relay; the Relay forwards upstream only if no existing upstream subscription exists.
• Teardown: Subscribers terminate subscriptions via STOP_SENDING frames and close SUBSCRIBE_NAMESPACE streams (FIN/RESET_STREAM). The Relay only sends STOP_SENDING upstream once all downstream subscribers have unsubscribed.

Proposal

• Agree the new text (clause A.3.3 + two figures) for inclusion in TR 26.836 v0.1.1.