proxy server A server
that sits between a client application,
such as a Web browser, and a real server.
It intercepts all requests to the real server to see if it can
fulfill the requests itself. If not, it forwards the request to
the real server.
Proxy servers have two
main purposes:
- Improve Performance: Proxy servers can dramatically
improve performance for groups of users. This is because it saves
the results of all requests for a certain amount of time. Consider
the case where both user X and user Y access the World
Wide Web through a proxy server. First user X requests a
certain Web page, which we'll call
Page 1. Sometime later, user Y requests the same page. Instead
of forwarding the request to the Web server where Page 1 resides,
which can be a time-consuming operation, the proxy server simply
returns the Page 1 that it already fetched for user X. Since
the proxy server is often on the same network as the user, this
is a much faster operation. Real proxy servers support hundreds
or thousands of users. The major online services such as Compuserve and
America Online, for example,
employ an array of proxy servers.
- Filter Requests: Proxy servers can also be used
to filter requests. For example, a company might use a proxy
server to prevent its employees from accessing a specific set
of Web sites.
