Is HTTP2 a change from TCP?

HTTP / 3: The next Hypertext Transfer Protocol simply explained

In order to understand what HTTP / 3 entails, it is first necessary to understand the function of QUIC, UDP and HTTP / 2 understand. HTTP / 3 is basically an amalgam of these components. The name HTTP-over-QUIC already contains the information that the data transfer takes place via UDP instead of TCP.

HTTP / 2 uses TCP as the most widely used transmission protocol on the Internet. TCP wraps connections over multi-level handshakes and transmits data packets chronologically. TCP does not continue transmission until a packet has been successfully transmitted. The transmission is secured via so-called Acks, i.e. Order and delivery confirmations and check numbers. Data transmitted via TCP contain a header with parameters that help sender processes to connect to peer processes of the recipient.

TCP is very reliable in terms of complete data transmission, but is associated with data congestion and loading times because all transmissions stop until one lost data packet is successfully transferred. With HTTP / 2, the internet protocol family is reaching its limits, as data transfer cannot be accelerated without new protocols.

Google thus proactively developed its own transfer protocol QUIC. QUIC bypasses TCP load congestion by using datagram-based and connectionless UDP transmission. UDP works like TCP on the transport layer, but dispenses with recipient-sender confirmations. Other streams do not have to wait for the previous one to be transmitted. Round trips between client and server are significantly shortened. The IETF recognized the advantages of the new protocol and introduced it in 2018 as the HTTP / 2 successor version HTTP-over-QUIC.

The principle of the HTTP transport protocol remains the same. It also consists of a header and message body and uses verbs, cookies and caching. The difference lies in the type of data transmission and the presence of built-in encryption.