Network services

HTTP/3 and QUIC

Also called HTTP/3, QUIC, h3, UDP 443, 0-RTT, Alt-Svc, connection ID, QPACK

HTTP over QUIC: a transport on UDP port 443 with TLS 1.3 built in and streams that do not block each other.

QUIC gives each stream its own ordering, so a loss delays only its stream; merges the transport and TLS 1.3 handshakes into one round trip (0-RTT to a known server); and names connections by connection ID, so they survive a change of address. Clients learn a site speaks it from Alt-Svc (h3=":443") or a DNS HTTPS record, then race QUIC against TCP; where UDP 443 is blocked, TCP (HTTP/2) wins and nobody notices. Headers use QPACK.

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