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.