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Table Of Contents  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)
                          9  HTTP Features, Capabilities and Issues

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HTTP Caching Features and Issues
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HTTP Security and Privacy
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HTTP Proxy Servers and Proxying
(Page 2 of 3)

Comparing Proxies and Caches

Proxying and caching are concepts that have a number of similarities, especially in terms of the impact that they have on basic HTTP operation. Like caching, proxying has become more important in recent years, and also complicates HTTP in a number of ways. The HTTP/1.1 standard includes a number of specific features to support proxies, and also addresses a number of concerns related to proxying.

The fact that both proxying and caching represent ways in which basic HTTP client/server communication is changed, combined with the ability of proxies to perform caching, sometimes leads people to think caches and proxies are the same, when they are not. A proxy is actually a separate element that resides in the HTTP request/response chain, where caches can be implemented within any device in that chain, including a proxy.

Another key way that caches and proxies differ is that caches are used “automatically” when they are enabled, where proxies are not. To use a proxy, client software must be told to use the proxy, and supplied with its IP address or domain name. The client then sends all requests to the proxy rather than to the actual server that the user specifies.

Note: Most of my explanations here have focused on hardware proxy servers, but proxies are also commonly implemented as software in a client device. A software proxy performs the same tasks of processing requests and responses; it is much cheaper to implement than a hardware proxy, but cannot be shared by many devices.



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HTTP Security and Privacy
Next Topic/Section

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Version 3.0 - Version Date: September 20, 2005

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