The TCP/IP Guide  9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)       9  TCP/IP Key Applications and Application Protocols            9  TCP/IP File and Message Transfer Applications and Protocols (FTP, TFTP, Electronic Mail, USENET, HTTP/WWW, Gopher)                 9  TCP/IP World Wide Web (WWW, "The Web") and the Hypertext Transfer Protocol (HTTP)                      9  TCP/IP Hypertext Transfer Protocol (HTTP)

HTTP Overview, History, Versions and Standards 1 HTTP Operational Model and Client/Server Communication

The Hypertext Transfer Protocol (HTTP) began as an extremely basic protocol, designed to do just one thing: allow a client to send a simple request for a hypertext file and receive it back from the server. Modern HTTP remains at its heart a straight-forward request/reply protocol, but now includes many new features and capabilities to support the growing size of the World Wide Web and the ever-increasing variety of ways that people have found to use it. The best place to start in explaining HTTP is thus by looking at its operation as a whole and how communication takes place between a Web server and a Web client.

In this section I introduce the Hypertext Transfer Protocol by describing its operation in general terms. I begin with a high-level overview of HTTP and discussion of its operational model. I explain the two types of connections that are supported between HTTP clients and servers, and the method by which requests can be pipelined in HTTP/1.1. I then provide more information about how persistent connections are established, managed and terminated in the current version of HTTP.

HTTP Overview, History, Versions and Standards 1 HTTP Operational Model and Client/Server Communication