Caching 101: Implementing Caches Transparently

By deploying the cache between the network and the end-users, ISPs get the full benefit of scalability and high performance without having to configure each browser.

by Amit Pandey
Director of NetCache, Network Appliance, Inc.
[May 28, 1999]

Q: What is the difference between a proxy cache and a transparent web cache?

A: A transparent cache acts much like a transparent firewall—it sits between the end users and the network and doesn't require the configuration of each browser. A proxy cache sits on the network and requires that each browser address the cache directly.

Q: What type of caching implementation should ISPs deploy to get the most benefit?

A: To take full advantage of caching, ISPs should deploy Web caches transparently, as a seamless part of the network infrastructure. This allows the ISP to capture the most browsers without configuring each browser for the cache. Web caches deployed transparently enable ISPs to easily retrofit their network for caching.

Q: Is any other equipment needed for transparent deployment?

A: For the highest performance, the current deployment is to integrate multiple Web caches with a Layer 4 (L4) switch, which partitions and balances Web traffic.

Transparent caches built on L4 switches can scale to arbitrary bandwidth because they group end user requests into separate buckets—mapping replicated data from a Web server to a single cache. When a switch detects that all caches for a given bucket are saturated, the switch simply forwards the TCP segments back to the WAN router, maintaining cut-through and freeing up the cache to handle other requests.

End

For more technical information on transparent deployment of Web caches, read the white paper, Transparent, Scalable, Fail-Safe Web Caching, by Dr. Peter Danzig and Karl L. Swartz .