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Web Performance Tuning by Patrick Killelea

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Proxy Servers

Proxy servers are usually set up at the interface between a large organization and the rest of the Internet, both for security and performance reasons. The main idea behind using a proxy for security is that there will be no direct connections between the Internet and the internal network; when an HTTP request goes out, the proxy intercepts it and makes the request on behalf of the internal user. Or if the proxy already has the page in its cache, the cache will simply return the page to the internal user without ever touching the Internet.

If the page requested is not in the proxy’s cache, then the request will be significantly slower because of the extra step of intercepting the request and copying it back from the proxy to the client. On the other hand, for all subsequent accesses, access will be far faster because the page is close at hand.

Proxy caches don’t work for dynamic content, or at least they’re not supposed to. If your proxy is caching dynamic content, the whole purpose of creating custom content on the fly is defeated. There are a few other twists with dynamic content. The images and other embedded static content on a dynamic page will be cached for an increase in performance, but HTTP 1.1 keepalives may actually hinder this use of cached images and lower performance. It depends on the sophistication of your proxy server. If the proxy checks only the first URL of the connection, it will not realize that it has usable images in the cache. Or, if the ...

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