One of the major benefits of using an Access Gateway to protect Web resources is that it can cache the requested information and send it directly to the client browser rather than contacting the origin Web resource and waiting for the requested information to be sent. This can significantly accelerate access to the information.
IMPORTANT:For caching to work correctly, the Web servers must be configured to maintain a valid time. If possible, they should be configured to use an NTP server.
The object cache on an Access Gateway is quite different from a browser’s cache, which all users access when they click the button and which can serve stale content that doesn’t accurately reflect the fresh content on the origin Web server.
The Access Gateway caching system uses a number of methods to ensure cache freshness. Most time-sensitive Web content is flagged by Webmasters in such a way that it cannot become stale unless a caching system ignores the Webmaster’s settings. The Access Gateway honors all RFC 2616 directives that affect cache freshness such as Cache-Control, If-Modified-Since, and Expires.
The Access Gateway can be fine-tuned for cache freshness in the following ways:
Accelerated checking of objects that have longer than desirable Time to Expire headers
Delayed checking of objects that have shorter than desirable Time to Expire headers
Checking for freshness of objects that do not include Time to Expire headers
Both the Access Gateway Appliance and the Access Gateway Service follow the RFC directives. In addition, the Access Gateway Service uses the “Apache Module mod_file_cache”.
The following sections describe the features available to fine-tune this process for your network: