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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)

TCP/IP Hypertext Transfer Protocol (HTTP) 1 2 3 HTTP General Operation and Connections

HTTP/1.1

While impatient pundits coined sarcastic terms such as the “World Wide Wait”, the IETF continued to work to improve HTTP. In January 1997, the first draft version of HTTP/1.1 appeared: in RFC 2068. This document was later revised and published as RFC 2616, Hypertext Transfer Protocol — HTTP/1.1, in June 1999. HTTP/1.1 retains backwards compatibility with both HTTP/1.0 and HTTP/0.9. It is accompanied by RFC 2617, HTTP Authentication: Basic and Digest Access Authentication, which deals with security and authentication issues.

HTTP/1.1 introduces several significant improvements over version 1.0 of the protocol, most of which specifically address the performance problems I just described. Some of the more important improvements in version 1.1 are:

• Multiple Host Name Support: In HTTP/1.0, there was no way to specify the host name of the server to which the client needed to connect. As a result, the Web server at a particular IP address could only support one domain name. This was not only inefficient, it was exacerbating the depletion of IP addresses in the 1990s, because each new Web server to come online required a new IP address. HTTP/1.1 allows one Web server to handle requests for dozens or even hundreds of different virtual hosts.
  
  
• Persistent Connections: HTTP/1.1 allows a client to send multiple requests for related documents to a server in a single TCP session. This greatly improves performance over HTTP/1.0, where each request required a new connection to the server.
  
  
• Partial Resource Selection: In HTTP/1.1, a client can ask for only part of a resource rather than the entire document, which reduces the load on the server and saves transfer bandwidth.
  
  
• Better Caching and Proxying Support: HTTP/1.1 includes many provisions to make caching and proxying more efficient and effective than they were in HTTP/1.0. These techniques can improve performance by providing clients with faster replies to their requests while reducing the load on servers, as well as enhancing security and implementing other functionality.
  
  
• Content Negotiation: A negotiation feature was added that allows the client and server to exchange information to help select the best resource or version of a resource when multiple variants are available.
  
  
• Better Security: HTTP/1.1 defines authentication methods and is generally more “security aware” than HTTP/1.0 was.

In addition to these notable improvements, many other minor enhancements were made in HTTP/1.1. Several of these take the form of new headers that can be included in client requests to better control under what circumstances resources are retrieved from the server, and headers in server responses to provide additional information to the client.

TCP/IP Hypertext Transfer Protocol (HTTP) 1 2 3 HTTP General Operation and Connections