Using a shared cache

It is common for a point of presence on the Web to have more traffic than a single server can handle. One solution is to simply add more servers. However, when multiple caching proxy servers are used, the contents of one cache often overlap with the contents of the other caches. In addition to unnecessary redundancy in storage, maximum bandwidth savings are not achieved because a cached file is re-fetched from the origin server when a request for it comes to a proxy server that does not have that file in its own cache. Although duplicate caching can be minimized by using a hierarchical chain of proxy servers, this scenario still results in additional traffic through a given server, and each additional link in the chain adds latency.

Cache sharing solves these problems by allowing each cache to share its contents with the other caches. Bandwidth savings result because of the following facts:

Two methods are provided for using multiple caches as if they are one logical cache:

RCA and ICP can be used together.