The Challenges of 0-RTT in IETF QUIC | Ian Swett

A key feature of HTTP/3 over QUIC is the ability to send a request in the first flight with the ClientHello. 0-RTT in IETF QUIC is notably more complex than gQUIC, with multiple packet number spaces and a limit on the amplification factor. Walk through some issues we hit and the tooling we used to identify and debug them before 0-RTT became a performance win for applications.