Research On The Resources Locating Models Of P2P System Based On DHT

As one of the important technologies of the Internet,the P2P(Peer-to-Peer) technology has been paid more and more attention for recent years in the computer field.Since P2P have some special characteristics,such as large-scale,dynamic state and distributed etc,therefore,how to retrieve information effectively in the system is a challenging problem.A DHT-based decentralized structured model, which avoids central managing and broadcast querying,has become a focus in the research area.Chord is a typical DHT-based system.However,as the logic keyword space is isolated from the real physical topology of the network,it weakens the data locality and the nodes in physical neighborhood may distributed far apart in logic ring of Chord.As a result,the system may have a large latency and downloading speed.Besides,it is regardless the peer's heterogeneity.In the thesis,we put forward a hierarchical P2P resources locating model based on Chord.The model consists of two rings:the main ring and the sub ring. Moreover chord has a poor performance because of redundant information in the finger table.In this thesis,an improved finger structure is presented for removing redundancy.The main ring is built up with super peers while the sub ring consists of normal peers,super peers and backup peers.The super peers,which help them search resources in the main ring,are more powerful and stable.Backup peers backup the data on super peers,and they will take charge the main ring when super peers fail to work.They begin their work as follows:First,a normal peer in a specific sub ring launches a resource query requirement,which will be routed in the sub ring according to the Chord protocol.Only in the case that the requirement is not met does the requirement be sent to super peers within the sub ring and be re-located in the main ring.Therefore,for the benefit of high efficiency in data locating and transporting,peers in physical neighborhood are distributed in the same sub ring and external resources are re-published in the local sub ring after downloaded from external network.The simulation result shows that the new algorithm does bring better performance in routing delay and hops of network than the original Chord Dual-chord and two-way Chord.