A two-level semantic caching scheme for super-peer networks

Recent measurement studies of file-sharing peer-to-peer networks have demonstrated the presence of semantic proximity between peers and between shared files. In this paper we tackle the problem of exploiting the semantic locality of peer requests to improve the performance of a P2P network by the use of semantic caches. Such caches group together peers with similar interests as well as files with similar request patterns. The resulting two-level caching infrastructure can be integrated in a very natural way with the superpeer concept. The super-peers in our system cache pointers to files recently requested by their client peers. The client peers, on the other hand, keep caches of super-peers that answered most of their requests in the past. As a consequence, peers with similar interests are grouped (clustered) under the same super-peers, and also files with similar request patterns are indexed by the same super-peers. We discuss the design choices and optimizations of the presented model. We also evaluate our system versus the network that uses only one level of semantic caches.