Expand description
The cloud relay backend of Session (ADR 0010).
When no candidate connected, the pilot may ask the signal server to carry the session: each party opens one WebSocket to the relay, the cloud pairs them by session id and forwards binary frames verbatim. The frames are the very bytes that would have been QUIC datagrams and control-stream bytes:
| byte 0 | rest |
|---|---|
1 | one datagram (a chunk, exactly as send_datagram would have sent it) |
2 | a segment of the control stream (NDJSON bytes, any split) |
Nothing above the transport knows the difference: the engine’s admission
control still measures a queued backlog against the profile’s threshold,
and the pilot’s reassembler still assembles chunks. The relay is TCP, so
loss is retransmitted rather than repaired by FEC, and a congested leg
shows up as backlog here (send_buffer_queued) instead of as QUIC loss.