1 The Proxy Server Squid - Novell LINUX ENTERPRISE SERVER 10 SP2 - INSTALLATION AND ADMINISTRATION Installation Manual

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The Proxy Server Squid
Squid is a widely-used proxy cache for Linux and UNIX platforms. This means that it
stores requested Internet objects, such as data on a Web or FTP server, on a machine
that is closer to the requesting workstation than the server. It may be set up in multiple
hierarchies to assure optimal response times and low bandwidth usage, even in modes
that are transparent for the end user. Additional software like squidGuard may be used
to filter Web contents.
Squid acts as a proxy cache. It redirects object requests from clients (in this case, from
Web browsers) to the server. When the requested objects arrive from the server, it de-
livers the objects to the client and keeps a copy of them in the hard disk cache. One of
the advantages of caching is that several clients requesting the same object can be served
from the hard disk cache. This enables clients to receive the data much faster than from
the Internet. This procedure also reduces the network traffic.
Along with the actual caching, Squid offers a wide range of features such as distributing
the load over intercommunicating hierarchies of proxy servers, defining strict access
control lists for all clients accessing the proxy, allowing or denying access to specific
Web pages with the help of other applications, and generating statistics about frequently-
visited Web pages for the assessment of the users' surfing habits. Squid is not a generic
proxy. It normally proxies only HTTP connections. It does also support the protocols
FTP, Gopher, SSL, and WAIS, but it does not support other Internet protocols, such as
Real Audio, news, or video conferencing. Because Squid only supports the UDP protocol
to provide communication between different caches, many other multimedia programs
are not supported.
The Proxy Server Squid 785