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When browsing the internet from a home PC, there are several elements
that make the whole process possible. First of all, on one end,
we have our home PC. This PC is connected via its modem to the ISP’s
server, which in turn is interconnected to servers around the world
that host the specific web sites that we are requesting.
From a web browser, we send a request to access a specific website
by typing the site’s address, for example, www.findproxy.org.
When we hit “Enter”, this request is sent to our ISP’s server,
which identifies the request. If the ISP has a proxy server with
cached requests, when retrieving our request it will look up the
information in its cache to determine if the proxy can comply or
not. This means that the proxy server saves all requests made from
users to its cache, so that the next time another user makes the
same request, it does not have to retrieve that same information
from the original server. The proxy server responds by sending the
information to our PC from its cache.
On the other hand, if the proxy server cannot comply, it will send
the request to the real server that hosts the specific website that
we are requesting. The host server sends that information to the
proxy server, which can then cache the response for future requests,
and then sends the information to our PC. Sometimes, more than one
proxy server can be involved, as some sites, like MSN, Yahoo, and
AOL have several proxy servers that respond to requests from their
cache, thus reducing the amount of petitions to the main server
and reducing response times.
In a corporate network, even more elements form part of the process.
Apart from the possibility of having its own proxy server to improve
performance, the proxy can also act as a filter from the employees’
terminal, blocking attempts to access specific content from their
web browsers. Additionally, companies have mail servers that store
and distribute emails over its local network and WAN. All potential
viruses are filtered at this stage before it can reach an employee’s
PC. Servers also provide additional security through firewalls either
from the proxy itself or from a firewall server dedicated to such
purpose.
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