2 / 5 HTTP/1.1, HTTP/2, HTTP/3 & QUIC

Wi-Fi to Cellular

A user walks out of the office mid-download. Their phone switches from Wi-Fi to cellular and its source IP changes. Over HTTP/2 the transfer stalls and restarts; over HTTP/3 it keeps going. What makes the difference?

A

HTTP/3 keeps a spare connection open over the second interface at all times and switches the transfer onto it as soon as the primary path stops delivering

B

QUIC identifies a connection by a connection ID rather than the IP and port four-tuple, so the endpoints keep the same connection and validate the new path

C

QUIC detects the interface change and immediately performs a fresh 0-RTT handshake from the new address, quickly enough that the transfer never visibly stalls

D

UDP is connectionless, so there is no state to lose and the packets simply arrive from the new address with no protocol involvement