Web Caching

Web Transport Protocols

Clients and servers use a number of different transport protocols to exchange information. These protocols, built on top of TCP/IP, comprise the majority of all Internet traffic today. The Hypertext Transfer Protocol (HTTP) is the most common because it was designed specifically for the Web. A number of legacy protocols, such as the File Transfer Protocol (FTP) and Gopher, are still in use today. According to Merit’s measurements from the NSFNet, HTTP replaced FTP as the dominant protocol in April of 1995.^[2] Some newer protocols, such as Secure Sockets Layer (SSL) and the Real-time Transport Protocol (RTP), are increasing in use.

HTTP

Tim Berners-Lee and others originally designed HTTP to be a simple and lightweight transfer protocol. Since its inception, HTTP has undergone three major revisions. The very first version, retroactively named HTTP/0.9, is extremely simple and almost trivial to implement. At the same time, however, it lacks any real features. The second version, HTTP/1.0 [Berners-Lee, Fielding and Frystyk, 1996], defines a small set of features and still maintains the original goals of being simple and lightweight. However, at a time when the Web was experiencing phenomenal growth, many developers found that HTTP/1.0 did not provide all the functionality they required for new services.

The HTTP Working Group of the Internet Engineering Task Force (IETF) has worked long and hard on the protocol specification for HTTP/1.1. New features in this ...