New Algorithms for Load Balancing in Peer-to-Peer Systems

Load balancing is a critical issue for the efficient operation of peer-to-peer networks. We give new protocols for several scenarios, whose provable performance guarantees are within a constant factor of optimal. First, we give an improved version of consistent hashing, a scheme used for item to node assignments in the Chord system. In its original form, it required every network node to operate O(logn) virtual nodes to achieve a balanced load, causing a corresponding increase in space and bandwidth usage. Our protocol eliminates the necessity of virtual nodes while maintaining a balanced load. Improving on related protocols, our scheme allows for the deletion of nodes and admits a simpler analysis, since the assignments do not depend on the history of the network. We then analyze a simple protocol for load sharing by movements of data from higher loaded to lower loaded nodes. This protocol can be extended to preserve the ordering of data items. As an application, we use the last protocol to give an efficient implementation of a distributed data structure for range searches on ordered data.