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Wajde

about browser&proxy caches ...

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hi guys , im new to networking. i read about browser's cache which created on client's pc. and then i read about proxy cache which more or less does the same job like browser's cache.. but there are somethings that i didnt get: 1) where do we install the proxy server (client pc or server)? 2) how do we configure it? 3) if i use home pc, where is the proxy server exactly? 4) whats the difference between browser's cache and proxy cache ? thanks

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Try Squid.

External caches make sense as soon as you have more than one browser connecting through same node, home/corporate LAN, ISP and similar.

Where you put it doesn't really matter, as long as the traffic between the computer and internet will run through it, and the connection between computer and proxy is somewhat "optimal". They are usually placed within a LAN, or operated by the ISP you're connecting through. Using other proxies usually isn't viable, or even possible, since they tend to be restricted to IP ranges.

The only advantage of a third party cache might be some additional filtering, and possibly larger cache size. It may also come handy if you use several browsers on same computer.

Other than that, caches shine when you have several browsers, accessing same domains regularly.

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but there is something that i didnt understand.
if a proxy server set on a Web Server , how this can help ???
if the client reaches the proxy it also reached the webserver!!!!! so that didnt save bandwidth !! the user already has a connection with the webserver even if he reached proxy!!!!

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Proxies are caches and have same characteristics.

For a given request, a response will be generated. What you need to figure out now is where to put the proxy, so that it will receive as many requests to which it can generate identical responses.

Quote:
if a proxy server set on a Web Server , how this can help ???


It doesn't. Proxies sit near groups of clients, not the target server.

Even then, there exist database specific HTTP proxies, which sit hidden on the server, and reduce workload on the database, by not executing pages that haven't changed.

Standalone proxies are nothing but HTTP caches. How effective they will be depends solely on where they are placed with regard to traffic that passes through them.

For example, a software development company uses MSDN. If they set up their web proxy somewhere on LAN, their requests msdn.com will be served mostly from local LAN, rather than querying MSDN every time. The potential savings here in terms of response times are pretty big, since LAN traffic is essentially free and considerably more scalable.

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You can answer your own question by just reading the answers you've already gotten. However, I will spell it out for you:

A browser cache sits in an individual browser client.

A proxy cache sits between a group of clients (for example, an office, or a school), and the greater web. Typically, you have very fast networking (Ethernet) between the clients and the proxy/cache, and slower networking (T1, DSL, etc) between the cache and the greater Internet.

An individual cache can only cache what an individual client has seen. If another client goes to the web and wants to get the same data, it has to be downloaded again over the slower network link.

If an individual goes through a proxy cache to the greater internet and requests some data, it will be cached both in the proxy and on the individual's machine. If another individual requests that same data within the cache lifetime from the same proxy, that individual's machine only needs to get the data from the proxy, not download it again over the slower Internet.

Thus, proxies are usually used by network administrators on campuses of businesses, schools and other organizations to improve performance on a limited Internet connection. For example, when everybody gets an e-mail linking to some funny video, then the first person to click the link will download the data for the video, but every person after that will get the cached copy from the proxy (assuming caching is set up right, etc).

There is one more possible use of a proxy. If you have a slow web server, say based on a large database and CMS system, but the output of that web server is cacheable, then you can make the "public" web server address be that of a proxy, and the proxy would in turn be redirected to the slow web server. That way, the proxy can remove redundant load from the slower web server.

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