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The University of Edinburgh

What is a "Proxy Cache"

Normally when your browser tries to display a web page it makes a direct network connection from your desktop computer to the web server holding the page you want. Instead of this direct connection it is possible to ask an intermediate machine, or proxy, to take your request and pass it on to the remote web server.

Such proxies may need to be used because of the type of network you are connected to or decisions taken by your network's administrator.

Many pages contain common images (for example the University's logo). Quite often you will use the 'Back' button to go to a page you have just been looking at. If your browser didn't have some memory it would have to ask again for the image or page every time you needed it. In order to make things work more quickly your browser keeps a collection of recently needed things in a 'cache'. But this cache is just for use by your browser on the one machine.

By using a web proxy cache service everyone's combined browsing ensures that copies of commonly accessed files are kept locally. Given enough space in the cache there is a good likelyhood of commonly used files (for example today's Dilbert cartoon) being already in the cache when you ask for it. That way you see it without having to wait for a connection to the remote server to be made. If you are the first person today to ask for it then there may be a short delay after which other users will reap the benefit of the local copy. So better and use of the available network bandwidth can be achieved and a more rapid response for your browsing. Additionally, we are exploring how we can protect you from downloading viruses to your desktop by installing virus scanners on the web proxy cache.