As mentioned previously, the first and primary protocol to transport over QUICis HTTP.

Much like HTTP/2 was once introduced to transport HTTP over the wire in acompletely new way, HTTP/3 is yet again introducing a new way to send HTTP overthe network.

HTTP still maintains the same paradigms and concepts like before. There areheaders and a body, there is a request and a response. There are verbs,cookies and caching. What primarily changes with HTTP/3 is how the bits getssent over to the other side of the communication.

In order to do HTTP over QUIC, changes were required and the results of thisis what we now call HTTP/3. These changes were required because of thedifferent nature that QUIC provides as opposed to TCP. These changes include:

  • In QUIC the streams are provided by the transport itself, while in HTTP/2the streams were done within the HTTP layer.

  • Due to the streams being independent of each other, the header compressionprotocol used for HTTP/2 could not be used without it causing a head of blocksituation.

  • QUIC streams are slightly different than HTTP/2 streams. The HTTP/3 sectionwill detail this somewhat.