A Hotspots-Free Overlay Cooperative Caching Scheme

Overlay Web caching (OCC) exploits resources of peers to provide scalable and cost-effective web caching service. In a typical OCC system, which is often characterized by highly heterogeneous node capacities and skewed query distributions, the resources of each node may be utilized in an unbalanced manner, i.e., some nodes are overloaded and become "hotspots". Unfortunately, there are no effective load balancing mechanisms in existing OCC systems to relief the "hotspots". This paper proposes a hotspots-free OCC scheme called HFOCC for multimedia content delivery service. Through replicating "hot" objects adaptively to lightly loaded nodes, loads are distributed more evenly across the whole network. Consequently, the hotspots are relieved. In order to utilize cache resource more effectively, HFOCC splits a node's cache space dynamically into two parts, namely the home cache and the replica cache, and manages them by a uniform policy. With a "soft" lifetime control mechanism, the redundant object replicas are deleted adaptively, and the system performs well under dynamically changing workloads. Experimental results show that HFOCC improves resource utilization and system throughput markedly.