A common proxy application is a caching Web proxy.
This provides a nearby cache of Web pages and files available on remote
Web servers, allowing local network clients to access them more quickly
or reliably.
When it
receives a request for a Web resource (specified by a URL), a caching
proxy looks for the resulting URL in its local cache. If found, it
returns the document immediately. Otherwise it fetches it from the
remote server, returns it to the requester and saves a copy in the
cache. The cache usually uses an expiry algorithm to remove documents
from the cache, according to their age, size, and access history. Two
simple cache algorithms are Least Recently Used (LRU) and Least
Frequently Used (LFU). LRU removes the least-recently used documents,
and LFU removes the least-frequently used documents.
Web proxies can
also filter the content of Web pages served. Some censor-ware
applications which attempt to block offensive Web content are
implemented as Web proxies. Other web proxies reformat web pages for a
specific purpose or audience; for example, Skweezer reformats web pages
for cell phones and PDAs. Network operators can also deploy proxies to
intercept computer viruses and other hostile content served from remote
Web pages. |
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