When the ISA server is installed in either Cache or Integrated mode, the Web Proxy Service is installed. The Web Proxy Service includes the Web caching facility. This feature allows the ISA server to cache HTTP and FTP (and Gopher) objects so that they can be accessed via the cache after the first request for the object is made. Web caching is one of the most common reasons for implementing a proxy server such as ISA Server. There are multiple advantages to using the Web proxy caching facility:

• Caching can reduce the total bandwidth used on the external interface.

• Caching can significantly reduce access times for popular content.

• Active caching allows popular Web objects to be refreshed automatically.

• Caching can reduce processor and network utilization at peak usage times.

All these advantages make a compelling argument for implementing a Web caching solution for your enterprise. ISA Server s caching mechanism is superior to that found in Proxy Server 2.0. Cached files are now stored in a single file where objects can be more rapidly searched and retrieved. ISA Server also can place virtually all of the cached elements into RAM, depending on how much memory is installed on the server. Retrieving cached objects from RAM greatly increases the speed at which Web objects can be retrieved.

Because the Web cache is a component of the Web Proxy Service, it is available only when ISA Server has been configured in Cache only or Integrated mode.