The frames are sent in multiplexed fashion and have a stream id. The receiver re arranges frames with the same stream id but what happens if an older frame arrives first?

Is there a concept of sequence number in http2.0 stream frames?

  • HTTP doesn't have any concept of frames. That's taken care of at a lower layer which usually, but is not required to, support that concept. – Blrfl Feb 7 at 13:25
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    @Blrfl: RFC 7540 Section 4 is titled HTTP Frames and specifies the framing layer of HTTP/2. – Jörg W Mittag Feb 7 at 13:43

At the moment, HTTP/2 is only specified for transport on top of TCP, which is a connection-oriented, reliable protocol, IOW it guarantees that packets are never re-ordered, duplicated, or lost. As long as the sender sends the frames in the correct order, they will arrive in the correct order.

Likewise, HTTP/3 is essentially HTTP/2 adapted for transport over QUIC instead of TCP. QUIC again, is a connection-oriented, reliable protocol like TCP, even though it is based on UDP.

In other words: as long as frames are sent in the correct order, they cannot be received in the wrong order, so there is no need to have provisions in the spec for that.

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