QUIC

QUIC (originally Quick UDP Internet Connections) is a modern transport-layer protocol developed by Google and standardized by the IETF. Instead of TCP it builds on UDP and embeds TLS 1.3 encryption directly into the transport layer. QUIC is the foundation of HTTP/3 and was designed to solve long-standing performance limits of the classic TCP + TLS stack.

How QUIC works

The key improvements QUIC brings over TCP are:

• Faster handshakes — QUIC merges the transport and encryption handshakes into one step, and on repeat connections it offers 0-RTT, sending data in the very first packet.
• Non-blocking multiplexing — many independent streams share one connection; a lost packet in one stream does not stall the others, eliminating the head-of-line blocking seen in HTTP/2.
• Connection migration — a connection is identified by a unique ID rather than an IP-address pair, so switching from Wi-Fi to mobile does not drop the session.
• Built-in encryption — all traffic is encrypted by default via TLS 1.3.

Because QUIC runs in user space (not the kernel like TCP), the protocol can evolve and update faster on the application side.

QUIC in practice

QUIC is already widely used across the internet:

1. Websites — browsers and servers speak HTTP/3 over QUIC, cutting load times especially on lossy mobile links.
2. CDNs — content providers serve assets over QUIC, improving TTFB and smoothing video delivery.
3. Server configuration — modern web servers (LiteSpeed, Nginx, Caddy) enable QUIC/HTTP/3, advertising it with the Alt-Svc header.

Enabling QUIC requires opening UDP port 443 on the firewall and an up-to-date server that serves HTTPS over TLS 1.3.