activeReadBeforeSend

[mwelzl]

The SCTP mapping excludes using a new stream of an already existing SCTP association on Initiate when activeReadBeforeSend is used. This is about the (unusual) pattern where the client opens and then reads without first sending anything. In SCTP, the server can't learn about the creation of a new stream unless the client sends data on it, so such stream mapping wouldn't work.

Is this different in QUIC? If yes, we must say how (because the general approach is to just send data). If not, we must also exclude using a new stream of an already existing connection when activeReadBeforeSend is used ("Preferred or Required").

[mwelzl]

RFC 9000 is a little bit ambiguous here: in Section 2, it just says: "Streams can be created by sending data", and there are no real indications in the text of "just creating without sending" being a part of the design. On the contrary, it is not a part of Section 2.4. So, to me, it's questionable if a QUIC API will offer "create a stream but don't send anything".

Then again, technically, it would be possible, since Section 19.8 says "When a Stream Data field has a length of 0, the offset in the STREAM frame is the offset of the next byte that would be sent." There are also rules on what to do when an unexpected STREAM frame arrives, but an error should only occur when it this happens on a "locally initiated stream"... so it seems that beginning a stream by sending a STREAM frame with no data is indeed quite okay.