Adding Structure to Unstructured Peer-to-Peer Networks: The Role of Overlay Topology

Abstract

Our work examines the role of overlay topology on the performance of unstructured peer-to-peer systems. We focus on two performance metrics: (a) search protocol performance, a local gain perceived directly by a user of the system and (b) utilization of the network, a global property that is of interest to network service providers. We present a class of overlay topologies based on distance between a node and its neighbors. We show, by simulation, that a particular topology instance of this class where every node has many close neighbors and few random neighbors exhibits better properties than other examined instances. In this overlay topology, the chances of locating files are high and the nodes where these files are found are, on average, close to the query source. This improvement in search protocol performance is achieved while decreasing the traffic load on the links in the underlying network. We propose a simple greedy algorithm to construct such topologies where each node operates independently and in a decentralized manner.