Research Of Data Location In Structured P2P Systems

In recent years, peer-to-peer (P2P) computing has become a popular network computing paradigm. Peer-to-peer systems can be classified into unstructured systems and structured systems according to network topology. Applications of structured P2P systems have spread over many fields. Data location is one of the important basic techniques in large-scale structured peer-to-peer system. In this thesis, data location technique of structured P2P systems is researched, based on the typical structured P2P system Chord, P2P construction algorithm, routing algorithm and data location algorithm is studied in detail.To resolve the disagreement between logical route and physical route in Chord application at present, based on network delay, a P2P construction algorithm DeChord is proposed. In order to get the latency of nodes, DeChord utilizes Global Network Position to compute the physical distance among nodes by mapping nodes in network into geometry area. Therefore, the closer peers in the physical network are always taken as neighbor peers, which can decrease the latency of every hop. The results of simulation proved that DeChord can decrease the latency of data location greatly contrasted with Chord, and the performance of algorithm is better with the increasing of nodes.To resolve the problem resulted from unilateral routing mechanism in Chord that the whole Chord ring is traversed to locate the neighbor peers on the counter-clockwise, a bidirectional routing mechanism algorithm BIRChord is proposed. BIRChord locates data from clockwise and counter-clockwise in the ring simultaneously, and bidirectional routing mechanism can make most lookup events accomplished through half the ring at most. The results of simulation indicated that BIRChord can decrease the hops in the process of data location compared with Chord, and the efficiency of data location is also improved.To resolve the problem that there are bottleneck nodes in the traditional routing path if large amounts of data are needed to be exchanged between the source node and the target node in the Chord ring, a routing chosen algorithm RCChord is proposed. In RCChord, the source node confirms the best routing path through computing the latency cost for every possible routing path according to the latency among nodes. The results of simulation indicated that the cost of routing path in RCChord is greatly reduced than that in Chord.