HTTP-2
Topics: HTTP
HTTP/2 multiplexes requests over TCP, so TCP-level head-of-line blocking can still occur.
Subtopics
Head of Line blocking
One form of Head of Line blocking in HTTP/1.1 is when the number of allowed parallel requests in the browser is used up, and subsequent requests need to wait for the former ones to complete. HTTP/2 addresses this issue through request multiplexing, which eliminates HOL blocking at the application layer, but HOL still exists at the transport (TCP) layer. HTTP/3 aims to solve this issue by using UDP as its transport layer protocol.