A Study Of Peer-to-Peer Systems Based On Topological Properties Of Overlay

Due to the technology growing swiftly, the demand and the user quantity keep a rapid increasing, peer-to-peer (P2P) systems become extreme dynamic and complex, and some of their topologies have been proved to exhibit strong power-law degree distributions and small-world phenomena found in many other real networks. However, the main difficulty in designing such systems is that currently, very little is known about the nature of topologies on which they would be operating. The result is that even simple algorithms or protocols, as in the case of Gnutella, could result in complex interactions that can adversely affect system performance.In this thesis, we focus our viewpoint upon these topological properties and conduct an extensive study on search technology of unstructured P2P networks with the theory of complex networks.Unstructured Peer-to-Peer (P2P) systems are largely self-organized and scalability. However, the loose overlay structure and the mechanism of a peer randomly joining and leaving a P2P network cause topology mismatching between the P2P logical overlay network and the physical underlying network. Meanwhile, due to the inefficient overlay topology, the flooding-based search mechanisms cause a large volume of unnecessary traffic. Aiming at alleviating the mismatching problem and reducing the unnecessary traffic, On the one hand we report an efficient algorithm for searching p2p networks. The algorithm, termed DNA, gets the topology of the network and resource information in the search phrase. Through the information obtained, we can decrease redundant messages and search the p2p networks efficiently. On the other hand we propose OTO(Overlay Topology Optimization) algorithm. The algorithm gets the current topology information through flooding queries among peers so as to alleviate the mismatching problem involving the optimization policy.