Scalable ultrapeer-based DHT protocol for file sharing

In this paper, we present a novel file searching protocol to structure a DHT ring consisting of only ultrapeers, not all the nodes. The DHT ring in this protocol is much less sensitive to the churn rate because ultrapeers have much longer uptime compared with leaf nodes. Thus, this feature makes the protocol more scalable and efficient than the previous DHT ones in terms of costs of file search, node join and leave operations and the number of routing table entries each node should maintain. Moreover, it is more effective for locating rare files than Gnutella-like searching protocols.