Abstract

This paper presents Cache Digest, a novel protocol and optimization technique for cooperative Web caching. Cache Digest allows proxies to make information about their cache contents available to peers in a compact form. A peer uses digests to identify neighbors that are likely to have a given document. Cache Digest is a promising alternative to traditional per-request query/reply schemes such as ICP. We discuss the design ideas behind Cache Digest and its implementation in the Squid proxy cache. The performance of Cache Digest is compared to ICP using real-world Web caches operated by NLANR. Our analysis shows that Cache Digest outperforms ICP in several categories. Finally, we outline improvements to the techniques we are currently working on.