Web Caching

Manual Proxy Configuration

A manual configuration is generally characterized by a set of proxy addresses, one for each transfer protocol, and a list of domain names for which the proxies should not be used. The set of proxyable transfer protocols includes HTTP, FTP, Gopher, SSL, and WAIS. Usually, a single proxy supports all of these, so the same proxy address is used for all protocols. Some clients allow you to set a single proxy address rather than requiring you to enter the same address repeatedly.

Depending on your reasons for using proxies, you may not need or want to configure all protocols. If your users are behind a firewall, it is probably necessary to proxy all requests. If not, you might want to proxy only HTTP and FTP. A proxy cannot cache SSL responses because the content is encrypted. Forwarding SSL requests when the client can make a direct connection serves only to increase the load upon the proxy. Gopher and WAIS requests might be cachable, but they typically comprise such a small fraction of total traffic that the cache provides relatively little benefit.

The manual configuration approach has a number of disadvantages. Primarily, it requires a significant amount of individual effort to enter all the settings. Knowledgeable users may not be bothered, but a typical user requires very clear and specific instructions. Additionally, you may need to provide different instructions for different browsers and different versions of the same browser. Another annoyance is ...