allowing multiple request-response exchanges to be exchanged on the same TCP connection, without the need for a new connection establishment phase for each request. However, accepting HTTP/1.1 connections does not support sending multiple requests at the same time, again causing blockages due to the increasing complexity of web pages.
About HTTP/2
HTTP/2, a derivative of the now obsolete SPDY protocol, introduced the concept of first-class streams embedded in the same connection. This allowed simultaneous multiplexing of buy phone number list requests and responses, but with one serious disadvantage: when the packet loss increases, HTTP/2 performance degrades due to the way TCP handles packet retransmissions (HOL blocking). The impact can be high because all wires use the same connection. When packet loss exceeds a given threshold, paradoxically, more HTTP/1 connections are more efficient than HTTP/2.
As mentioned, QUIC has first-class streams that solve the problem of slow connection latency, as in HTTP/2. In addition, it processes them separately from each other, which solves performance issues due to packet loss. Using QUIC as a transport layer protocol is the biggest improvement over HTTP/3 over HTTP/2. Because QUIC initially implemented a number of flow-related features that were an integral part of the HTTP/2 specification, they could have been removed from HTTP/3. In addition, the implementation of QUIC was required to create a new HTTP header compression scheme, QPACK, because HTTP/2 HPACK header compression depends largely on the order in which TCP delivers packets to endpoints.