muMuQUIC: Micro-Multicast for QUIC

Abstract:

Delivering the same content to many receivers over QUIC currently requires either one unicast connection per receiver or a substantial protocol extension. Flexicast QUIC solves the problem by building on Multipath QUIC, but in doing so it inherits the full multipath machinery — path probing, per-path nonce computation, and the rest — much of which flexicast delivery never exercises. This report asks how much of that machinery can be discarded, and how much must be reinvented in its place.

The answer is muMuQUIC (micro-multicast QUIC), a roughly 320-line specification. A server sends ordinary 1-RTT short-header packets to an IP source-specific multicast group. The only departures from a unicast packet are that the Destination Connection ID carries a Flow ID and that packet protection uses a flow-specific key, derived from a shared secret by the unmodified RFC 9001 procedure. Clients learn the group address, port, Flow ID, cipher suite and secret over their existing unicast connection through a single new frame, then feed multicast packets into their normal receive pipeline. Only DATAGRAM frames are carried. muMuQUIC deliberately provides no reliability, no congestion control and no source authentication.

The design was validated at the IETF 126 Hackathon in Vienna, where participants implemented it in six independent QUIC stacks in under 1.5 days and used it to deliver a live RTP video stream from a webcam to a laptop and two smartphones.

Recommended citation: Navarre, L., & Bonaventure, O. (2026). muMuQUIC: Micro-Multicast for QUIC.
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