QUIC
QUIC is a new multiplexed transport built on top of UDP. HTTP/3 is designed to take advantage of QUIC's features, including lack of Head-Of-Line blocking between streams.
The QUIC project started as an alternative to TCP+TLS+HTTP/2, with the goal of improving user experience, particularly page load times. The QUIC working group at the IETF defined a clear boundary between the transport(QUIC) and application(HTTP/3) layers, as well as migrating from QUIC Crypto to TLS 1.3.
Because TCP is implemented in operating system kernels and middleboxes, widely deploying significant changes to TCP is next to impossible. However, since QUIC is built on top of UDP and the transport functionality is encrypted, it suffers from no such limitations.
Key features of QUIC and HTTP/3 over TCP+TLS and HTTP/2 include[1]
- Reduced connection establishment time - 0 round trips in the common case
- Improved congestion control feedback
- Multiplexing without head of line blocking
- Connection migration
- Transport extensibility
- Optional unreliable delivery
Algorithm
Client key change generation
The connection begins with the client generating a private/public keypair for key exchange. Key exchange is a technique where two parties can agree on the same number without an eavesdropper being able to tell what the number is.
The private key is chosen by selecting an integer between 0 and 2^256-1. The client does this by generating 32 bytes (256 bits) of random data. The private key selected is:
202122232425262728292a2b2c2d2e2f303132333435363738393a3b3c3d3e3f
The public key calculated is:
358072d6365880d1aeea329adf9121383851ed21a28e3b75e965d0d2cd166254
Ref: