Implementing ISA Server in Cache Mode

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

ISA Server in cache mode accelerates Web access performance by caching Internet content locally. ISA can provide access control for Web content, both in forward cache mode and reverse cache mode.

Forward Cache Mode

When a client in the internal network requests a Web page, ISA Server in forward cache mode checks if the content is cached locally. If so, the request is not forwarded to the Internet, and the forward cache server returns the Web pages to the client. If the Web page is not stored locally, ISA Server (acting on behalf of the client) retrieves the Web page from the Internet. ISA Server then saves that Web page in the local cache. The next time a client requests that page, ISA Server can fulfill the request without going to the Internet to retrieve the page. This results in using less bandwidth on the Internet connection. Figure 5.4 illustrates a forward cache mode configuration.

Figure 5.4   ISA Server in Forward Cache Mode

Reverse Cache (Web Publishing) Mode

You can also configure ISA Server in reverse cache mode. ISA Server in reverse cache mode caches content provided to the Internet from the Web server. When an Internet client requests a Web page, the request is sent to the ISA Server–based computer first. If the page is stored there locally, there is no need to retrieve the page from the Web server. This increases performance for Internet clients accessing the Web site from the Internet, as well as increasing security for the server. Figure 5.5 illustrates a reverse cache mode configuration.

Figure 5.5   ISA Server in Reverse Cache Mode