Networking

QUIC

UDP-based multiplexed and secure transport — the substrate of HTTP/3.


In plain terms

Per-stream loss recovery (no TCP HOL), 0-RTT resumption, integrated TLS 1.3, connection migration via connection ID.

Origin

Started at Google in 2012 as a TCP-replacement experiment ("Quick UDP Internet Connections"). Iteratively standardised at the IETF over 2016–2021; the IETF version diverged from Google's original. RFC 9000 published May 2021. HTTP/3 (RFC 9114) followed in 2022.

Where it shows up in production
  • Google services YouTube, Maps, Search — most Google traffic now runs over QUIC by default in Chrome.
  • Cloudflare Serves HTTP/3 to all customers since 2019. About 30% of their HTTPS traffic is QUIC.
  • Facebook & Meta mvfst (their QUIC implementation) carries the bulk of native-app traffic.
On Semicolony
Sources & further reading
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