Http3

HTTP/3 runs QUIC over UDP:443, and the reason to care is what a lost packet costs. On a TCP connection every stream shares one byte stream, so a dropped segment blocks delivery of everything behind it until the retransmission arrives. QUIC gives each stream its own loss recovery, so the same drop blocks only the streams whose data was in that packet. ...

The next version of HTTP moves from TCP to QUIC, a transport with its own reliability built on UDP. The payoff is that packet loss on one stream no longer stalls the whole connection the way it can on TCP with HTTP/2. ...