Oasis: A Hierarchical EMST Based P2P Network

Peer-to-peer systems and applications are distributed systems without any centralized control. P2P systems form the basis of several applications, such as file sharing systems and event notification services. P2P systems based on Distributed Hash Table (DHT) such as CAN, Chord, Pastry and Tapestry, use uniform hash functions to ensure load balance in the participant nodes. But their evenly distributed behaviour in the virtual space destroys the locality between participant nodes. The topology-based hierarchical overlay networks like Grapes and Jelly, exploit the physical distance information among the nodes to construct a two-layered hierarchy. This highly improves the locality property, but disturbs the concept of decentralization as the leaders in the top layer get accessed very frequently, becoming a performance bottleneck and resulting in a single point of failure. In this paper, we propose an enhanced m-way search tree (EMST) based P2P overlay infrastructure, called Oasis. It is shown through simulation that Oasis can achieve both the decentralization and locality properties along with high fault tolerance and a logarithmic data lookup time.