A new and effective hierarchical overlay structure for Peer-to-Peer networks

The tremendous growth of public interest in Peer-to-Peer (P2P) networks in recent years has initiated a lot of research work on how to design efficient overlay structures for P2P systems. Scalable overlay networks such as Chord, CAN, Pastry, and Tapestry provide no control over where data is stored and the location of the peers and resources is determined by the hash values of their identifiers and keys respectively. As a result, these overlays cannot support range queries and other proximity-aware complex queries directly.In this paper, we present a hierarchical P2P overlay network called SkipCluster, which is capable of supporting both exact-match and multi-dimensional range queries efficiently without consumption of extra memory space. SkipCluster is derived from skip graphs and SkipNet, but it has a two-tier hierarchical architecture.In both tiers, peers are connected in sequence according to the order of their peer IDs, and related resources are stored near each other without hashing of their resource keys. We design a novel data structure called Triple Linked List (TLL) to store each super-peer’s pointers in the higher tier, which can be used to find the longest prefix and speed up query routing of inter-cluster. In the lower tier, each intra-cluster peer’s routing table contains pointers with exponentially incremental distance. Experimental results show that SkipCluster can speed up both exact-match and range queries in different network sizes.