The QUIC protocol

QUIC is a general-purpose network protocol built on top of UDP. The protocol is still under development and standardized by the IETF. Quinn strives to implement the latest draft but may lag a bit behind. Although QUIC is still in a draft phase, the protocol is used for all connections from Chrome web browsers to the Google servers.

QUIC solves a number of transport-layer and application-layer problems experienced by modern web applications. It is very similar to TCP+TLS+HTTP2, but implemented on top of UDP. Having QUIC as a self-contained protocol allows innovations which aren’t possible with existing protocols as they are hampered by legacy clients and middleboxes.

Key advantages of QUIC over TCP+TLS+HTTP2 include:

• Improved connection establishment speed (0-rtt).
• Improved congestion control by moving congestion control algorithms into the user space at both endpoints.
• Improved bandwidth estimation in each direction to avoid congestion.
• Improved multiplexing without head-of-line blocking.
• Contains forward error correction (FEC).

While QUIC's intentions are originally web-oriented, it offers interesting opportunities in other areas like game networking. One thing is for sure, QUIC has many great potentials and will serve us in the future with HTTP/3.

In the upcoming chapter we will be discussing various aspects of QUIC also in relation to Quinn.