ISPPlanet Cache Review Series - Quantex WebXL

Designing Your Cache Network
WebXL can simultaneously support three caching modes: forward proxy, transparent proxy, and reverse proxy. Forward proxy requires the usual browser reconfiguration. Reverse proxy (aka Web Server Acceleration) uses DNS to resolve a web server's name to the WebXL's address. The WebXL either returns cached content or forwards requests proxied servers in a rotating round-robin sequence for load distribution and fail-over.

Transparent proxy can be accomplished in four ways:

1. Use the WebXL as an in-line router (a gateway / proxy firewall)
2. Use a layer 4 switch (e.g., Foundry, Alteon) to forward HTTP to the WebXL
3. Use a WCCP (Cisco Web Cache Coordination Protocol) router to forward HTTP to the WebXL
4. If the WebXL and clients are on the same subnet, use the WebXL as a default gateway for clients. The WebXL will re-route non-HTTP traffic to its own default gateway (the next-hop router).

We tested the WebXL in forward mode, transparent modes 1 and 4 above, and reverse mode. While many ISPs prefer transparent mode to eliminate browser changes, beware that WebXL currently only caches FTP in proxy mode.

Hierarchies can be used to distribute caching workload. The WebXL can act as a CERN client, an ICP server, and an ICP client. Use CERN if you've already invested in other (older) cache servers. Otherwise, use ICP to build a network of client, parent, and peer caches. When ICP is enabled and content is needed, the WebXL sends queries to all ICP peers and parents. If none responds positively, the WebXL sends a content request to one ICP parent, who fetches the objects.