A Two-Level Caching Protocol for Hierarchical Peer-to-Peer File Sharing Systems

In hierarchical Peer-to-Peer (P2P) systems, several selected peers are promoted as super-peers to provide an efficient lookup service for the ordinary peers, although it would cause a service bottleneck and a heavy workload at the point of the promoted peers. In this paper, we propose a two-level caching architecture consisting of level-1 cache and level-2 cache to relax such bottlenecks in hierarchical P2Ps. Each cache is partitioned into two parts so that it could manage both of static and dynamic data in a space-efficient manner, where static data indicates popular pages which are frequently requested by many users and dynamic data indicates pages which may not be popular but repeatedly requested during a short time period. The performance of the proposed method is evaluated by simulation. The result indicates that our caching protocol significantly reduces the network traffic and exhibits a high hit rate even in small cache sizes.