Due to its exponential growth, the World Wide Web is increasingly experiencing
several problems, such as hot spots, increased network bandwidth usage, and excessive
document retrieval latency. The standard solution to these problems is to use
a caching proxy. However, a single caching proxy is a bottleneck: there is a limit
to the number of clients that can use the same cache, and thereby the effectiveness
of the cache is limited. Also, a caching proxy is a single point of failure. We
address these problems by creating a protocol allowing multiple caching proxies
to cooperate and share their caches, thus increasing robustness and scalability.
This scalability, in turn, gives each client an effectively larger cache with
a higher hit rate. This paper describes a prototype implementation of this protocol
that uses IP multicast to communicate between the servers.