draft-gurel-moq-probing-00 | Individual submission | -00 posted 2026-10-12 | 27 pages | Standards Track | Datatracker
Authors
- Zafer Gürel (moqtail)
- Ali C. Begen
- Deniz Ugur
Abstract
A standards-track moq-transport extension that defines probe tracks — synthetic, on-demand media streams a MoQT endpoint uses to measure the available bandwidth on a single connection hop before switching to a higher-quality representation. The problem it solves is fundamental to adaptive delivery: a subscriber receiving a 1 Mbps track only ever learns that at least 1 Mbps is available — the throughput measurement is capped by the media’s own bitrate, so it cannot tell whether a 3 Mbps rendition would sustain. Probe tracks let an endpoint deliberately generate measurable traffic at a chosen rate without perturbing the real media, and — crucially — without the probe being cached or forwarded beyond the hop it targets, so the measurement reflects that hop alone rather than an end-to-end path.
Key Technical Details
- Two probe directions.
- Downlink probe — the subscriber requests a probe via
SUBSCRIBEin the(.session, .probe)namespace; the relay (or publisher) synthesizes objects to fill the measured capacity toward the subscriber. - Uplink probe — the publisher generates objects into the
(.session, .sink)namespace; the relay consumes (sinks) them, measuring the publisher→relay hop.
- Downlink probe — the subscriber requests a probe via
- Session-scoped, non-forwarded. Probe tracks live under reserved session-local namespaces and are terminated at the target hop — they are never cached nor relayed onward, so a probe measures exactly one link.
- Probe “shapes”. Probes are parameterized by a shape — e.g. paced (deliver at a target rate) or greedy (bulk transfer to saturate the link) — with the shape parameters encoded in the track name and resolved deterministically by both endpoints, so no extra negotiation message is needed.
- Complements, not replaces, padding. It positions relay-managed probe tracks alongside MOQT’s existing object padding mechanism, adding an explicit, controllable measurement capability rather than relying on incidental padding.
Relationship to other work
- A media / ABR building block. Bandwidth headroom estimation is the input switch-based ABR and rate adaptation need to decide when to step up a rendition — squarely in the wiki’s media focus area. Where moq-subscription-flow-control bounds what a publisher may push, this draft measures what a hop can carry.
- Authored by the moqtail team. Zafer Gürel and Ali C. Begen maintain moqtail; this is the second Gürel-authored individual input of the week after moqtail’s draft-18/20 wire work, and it lands during the Seattle interim.
- Part of the October individual-draft flurry. It is the newest MoQ document on the datatracker (Oct-12), ahead of [[moq-discovery|
draft-jennings-moq-uri-00]] (Oct-7), moq-subscription-flow-control (Oct-7), moq-end-to-end-delivery-timeout (Oct-6) and the two timestamp drafts.
Notes
Individual submission by Zafer Gürel, Ali C. Begen and Deniz Ugur; not WG-adopted. Posted 2026-10-12, during the Oct 12–15 Seattle hybrid interim. See adaptive-bitrate, switch-abr, moq-transport, moqtail, discussions-2026-10.