QUIC
also called HTTP/3
A transport built on UDP that provides streams, encryption and congestion control, removing TCP's head-of-line blocking and reducing connection setup latency.
QUIC reimplements what TCP provides, in user space, over UDP — which lets it fix things TCP cannot change without breaking the internet.
Per-stream ordering, so a lost packet stalls only its own stream rather than every multiplexed request. This is the main win on lossy or mobile networks.
Encryption built in, with the TLS handshake integrated into the transport handshake — so connection setup is one round trip, or zero for a resumed connection.
Connection migration: a connection is identified by a connection ID rather than by the IP/port four-tuple, so a phone switching from Wi-Fi to cellular keeps its connection instead of reconnecting.
Costs: UDP is sometimes blocked or deprioritised by middleboxes, and processing in user space uses more CPU than kernel TCP at high volume.