ISPPlanet Cache Review Series - Quantex WebXL

Fine-Tuning Cache Behavior
ISPs who have deployed caches will tell you that quick and easy bypass configuration is very important. For some sites, caching can have undesirable side-affects, ranging from session timeouts to authentication failures. WebXL handling of objects with ?, /cgi, and NO-CACHE reply headers can be customized to efficiently reduce these problems (for example, do not cache but split replies for concurrent requests without cookies). When short-term or persistent problems do occur, ISPs require the ability to circumvent the cache for specified sources and destinations. Sources are bypassed with Client Acceleration Exception IPs.

Destinations are identified by host/domain name, path name, and/or file extension on the Bypass panel. We had no luck testing this feature. According to log files, bypassed content was served from the cache (Quantex is investigating). While a layer 4 switch could quickly bypass entire subnets, the ability to specify subnets and path names with regular expressions would be a nice extension here.

The WebXL supports HTML 1.1 tags to ensure cached content stays fresh. If an individual cached object does not have a time to live, it is refreshed every 6 hours. Tuning parameters are available to customize HTTP, FTP, and Gopher refresh intervals and control how long unreferenced objects remain "hot" (available for fastest retrieval).

Admins can proactively refresh specified sites by configuring Downloads on an hourly, daily, or one-time scheduled basis; a "download now" button would also be nice. Parameters define maximum object sizes and levels to control resource usage. The WebXL does not appear to provide any predictive pre-fetch. Monitoring tools (see Monitoring the WebXL) could provide more resource usage info to facilitate fine-tuning.

ISPs will appreciate the ability to customize the splash screen presented to clients proxied through the WebXL.