An analytical comparison of cooperation protocols for Web proxy servers

Sharing cached documents among cooperative Web proxies is an effective solution to reduce Web traffic and alleviate network bottlenecks. This paper aims at comparing the performance of two cooperation protocols which follow opposite approaches: the Internet Cache Protocol (ICP) and the Full Informed Protocol (FIP). The former activates information exchange among proxies on client demand; the latter guarantees that any proxy is kept informed about the cache content of all the other cooperative proxies. The performance comparison is carried out through analytical models determining under which conditions one protocol outperforms the other. Our analysis shows that ICP is often preferable to FIP, thus pointing out that the client demand based approach is an effective solution for proxy cooperation.