QUIC

QUIC (Quick UDP Internet Connections) is a transport layer network protocol designed to reduce connection and transport latency for web traffic. It runs over UDP and combines multiplexed streams with strong encryption, aiming to replace TCP plus TLS for many applications, notably HTTP/3. A QUIC connection provides reliable, in-order delivery within streams, while allowing multiple streams to be active concurrently within a single connection to avoid head-of-line blocking.

History and standardization: QUIC was originally developed by Google in the 2010s to improve web performance, with early experiments and deployments in Chrome and Google services. The IETF began standardizing QUIC in the mid-2010s, resulting in the IETF QUIC specification, published as RFC 9000 (transport) and RFC 9001 (TLS over QUIC) in 2021. Today, the IETF QUIC is the standardized version and is what is widely deployed.

Design and features: QUIC uses UDP, supports 0-RTT and 1-RTT handshakes to reduce latency, and integrates TLS 1.3 into the transport handshake. It provides connection-level cryptographic keys and per-connection state. It supports multiple independent streams with their own flow control, and streams can deliver data out of order relative to each other. QUIC includes built-in congestion control, loss recovery, and mechanisms for connection migration when IP address changes.

Deployment and impact: The protocol is the foundation for HTTP/3 and is increasingly deployed by major browsers and services. Because it runs over UDP, it can be blocked on some networks; however, it offers reduced latency and improved performance in supported environments. Ongoing improvements focus on security, tooling, and interoperability.

Security and considerations: QUIC provides end-to-end encryption and aims to reduce exposure to man-in-the-middle and buffering attacks, but 0-RTT data can be vulnerable to replay attacks and has trade-offs in terms of forward secrecy and security. Network operators monitor QUIC traffic, as with other UDP-based protocols.