Directory Structures for Collective Internet Caches Efficient directory management is the key design problem for any Internet cache. Load on the internal network. Important to almost all configurations, internal network usage affects link contention and congestion and the potential for lost packets on the network connecting the caching servers, e.g., an ISP's internal network. Costs of external network usage.
Web caches exist in part to reduce bandwidth demands on the external network.
A second reason is that caches can directly affect access costs when Internet access charges are metered by traffic volume. Object fetch latency. From the perspective of an individual client, object fetch latency is the most important motivation for using a Web cache, and the only real measure of its success. Latency of the internal network. As the network distance between the servers in a collective cache increases, synchronous network exchanges with remote parts of the cache are no longer practical.