Study On Resources Locating Technology Of Structured Peer-to-peer Networks Based On Heterogeneity Of Peers

P2P (Peer-to-Peer Network) is a system with completely decentralized self-organization and resource usage. It is a research hotspot which has replaced the traditional"client/server"computing pattern on account of its efficient, high scalability and good fault-tolerance etc. In recent years, the continuous growth of Internet resources is accompanied by increasing requirements of a diversified wealth of P2P applications. How to locate resources efficiently with the lowest load factor has become an important issue to meet these challenges. In contrast to centralized server applications, for which the location of data items is inherently known, P2P systems store resources in multiple locations within the system. There are two main approaches which have been developed to solve this problem: structured approaches and unstructured approaches. Structured approaches outperform unstructured approaches in scalability, reliability and fault tolerance. But a large heterogeneity among peers and too much information redundancies in routing table bring inefficient routing with higher network overhead in structured P2P networks. The thesis proposed a two-tier bidirectional search system, which improved the network topology, routing strategy and self-orgnization strategies of Chord and get higher efficiency with lower network overhead.At first, the thesis introduces the basic notions of P2P network and summaries the progress of the domestic and foreign relate researches. After an in-depth research on the DHT (Distributed Hash Table) routing principles and Chord protocol, hierarchical P2P systems became a suitable approach to solve the problems of peers'heterogeneity. Then the thesis chooses an optimal hierarchical structure with minimal network load from four typical hierarchical structures. On this basis, the thesis proposed a two-tier bidirectional search system with a new routing table optimization strategy, a new node arrival algorithm and a new node failure handling mechanism by the improvement of Chord. On the new routing table optimization strategy, too much information redundancies are instead by a piece of useful routing information. By using corresponding routing algorithms, the resource searching efficiency is improved. The node arrival algorithm take peers'absolute performance and relative performance into account at the same time in order to avoid inefficient routing resulted from error estimation of peers'absolute performance. In addition, the node failure handling mechanism maintains the stability of system performance by connecting nodes'new successors initiatively. In the end,to validate the performance of the two-tier bidirectional search system in real network environment, mathematical analysis and P2Psim simulator are used to compare the system's performance with Chord and Bidirectional Chord. The results show that the two-tier bidirectional search system can advance the systems'performance.