What Is QUIC?

Date First Published: 10th June 2022

Topic: Computer Networking

Subtopic: Internet Protocols

Article Type: Computer Terms & Definitions

Difficulty Level: 9/10

Learn more about what QUIC is in this article.

QUIC stands for Quick UDP Internet Connections and it is a transport-layer protocol that was designed by Google on 12th October 2012. The aim of QUIC was to be equivalent to a TCP connection, but with reduced latency. QUIC is pronounced ‘quick’. Other browsers, such as Microsoft Edge and Firefox support it. On Safari, it is implemented but disabled by default. QUIC was standardised by the IETF as RFC 8999, supported by RFC 9000, RFC 9001, and RFC 9002 in May 2021.

QUIC Changes

QUIC introduces four changes, which include:

• Reduced connection times – Most HTTP connections use TLS. QUIC makes the exchange of keys and supported protocols part of the handshake process. When a connection is made, the response packet will include the data required for future packets to use encryption, making it unnecessary for the TCP connection to be set up and the security protocol to be added through additional data packets. A TLS handshake is a long process, since there are 4 round-trip requests required. Transmitting the data over TCP adds even more steps to the process, causing the connection to slow down. All of this is replaced by a single handshake by QUIC.
• Using UDP as the transport protocol rather than TCP. This does not include recovery of lost data packets. Instead, each QUIC stream has its own flow control, and lost data is retransmitted at the QUIC level rather than the UDP level. This means that if one stream experiences an issue, the communication protocol can still handle other streams separately. This can help improve speed on lines that are vulnerable to errors because, in most cases, a lot more data is received before TCP recognises a broken or missing packet, and all of that data is blocked or discarded whilst the error is fixed. This data can be processed in QUIC whilst the single multiplexed stream is restored.
• Stable connections when networks are changed – If a user is connected to a mail server using TCP and their network changes (e.g. from Wi-Fi to 4G), every connection would time out and would need to be reestablished. However, QUIC enables better movement from one network to another by providing each connection to a server with a unique identifier, which can be reestablished by sending a data packet rather than making a new connection.
• It is easier to improve and develop – Since QUIC can be implemented on the application level, it is a much more flexible protocol. TCP is implemented in operating system kernels, making it almost impossible to change it.