PROXY SERVERS

What exactly is a proxy server? What does it do? Thedictionary defines proxy as the authority or power to act for or on behalf ofanother. That’s exactly what a proxy server does. Proxy servers areimplemented on networks that connect to the Internet, through a dial-upconnection or otherwise. For the clients on the network, the proxy serverrepresents the Internet (or at least a microcosm of the Internet), and to theInternet, the same proxy server acts on behalf of all the clients on thenetwork. Let’s see how this works.

A proxy server is installed on the network, at or near itspoint of connect to the Internet. It intercepts all requests to the Internet forWeb pages, etc, and tries to fulfill them locally. If it doesn’t have the pagein local storage (called cache), then it fetches the page from the Internet. Theproxy server stores a local copy of all such pages, and the next time someonerequests the same page, it serves the page from its local storage rather thanfetch it again from the Net.

What are the advantages of having such a setup?

For starters, a proxy server makes Internet access faster.How? Consider an office with say a hundred people. Chances are that most of themwould be visiting the same pages again and again. If the proxy server saves suchpages locally, then people requesting for those pages again will not have towait for the pages to travel to them all the way from servers located half theworld away. They will be able to access them instantaneously over the localnetwork.

This leads us to the second benefit of having proxy servers–conservingbandwidth. If the requested page is served off a local machine (the proxyserver) then you will not use already scarce bandwidth to download that page.So, other applications or page requests that can’t be satisfied by the proxyserver and have to actually go out to the Internet, get more bandwidth and, inturn, become faster themselves.

The third benefit of installing a proxy server is thatadministrators need not go and configure hundreds of systems for access rights.For example, if you want to avoid access to certain functionalities, saydownloading of streaming music and movies, you can easily do that at the proxyserver than by, say, sending out ineffective circulars.

Proxies handle requests they get according to protocols. Byenabling or disabling selected protocols, you can enable or disable access tospecific services. For example, you can disable instant messaging, or streamingmedia. Also, you can grant or deny access based on time, client name, networkaddress, etc.

Not all proxies support all protocols. Thus, if a proxy doesnot support a particular protocol, say the SMTP protocol, then you cannot routethat service (in this case, the sending out of mail) through that proxy. So, youneed to first check out the protocols you need supported, and the protocolssupported by the particular proxy server, before you decide on one to use onyour network.

Most proxies today also offer built-in firewall capabilities.That is, they can also act as your first level of security against intrudersfrom the Internet into your local network.

It’s not only on local networks that proxy servers areinstalled. They are implemented all across the Internet to make Net accessfaster. ISPs implement proxy servers at their local nodes to provide fasteraccess to their clients. Moreover, large networks can benefit from multipleproxy servers. In the article on cascading proxy servers (page 109 in thisissue), we’ll discuss how this is done.

If you run a network that provides shared access to theInternet, you should run a proxy server to improve access speeds, if not tomanage and control access rights.

Krishna Kumar