HTTP: The Definitive Guide
Chapter 4. Connection Management
The HTTP specifications explain HTTP messages fairly well, but they don't talk much about HTTP connections, the critical plumbing that HTTP messages flow through. If you're a programmer writing HTTP applications, you need to understand the ins and outs of HTTP connections and how to use them.
HTTP connection management has been a bit of a black art, learned as much from experimentation and apprenticeship as from published literature. In this chapter, you'll learn about:
How HTTP uses TCP connections
Delays, bottlenecks and clogs in TCP connections
HTTP optimizations, including parallel, keep-alive, and pipelined connections
Dos and don'ts for managing connections