The Research On Searching Mechanism In Chord Networks

Peer to peer network (P2P) is a revolution to the traditional Client/Server network architecture.Each node in P2P can share a large amount of data with others. With the scale of the P2P network growing, it can rapidly accumulate inflated information and provide a rich information warehouse for users.Consequently,an efficient search scheme for users to retrieve needed data quickly and accurately is required emergently.Present research concentrates on improving location efficiency, load balance, scalability and etc.Besides centralized systems,P2P networks can be roughly classified into two categories:unstructured and DHT-based structured P2P networks.Searching mechanisms in unstructured P2P networks are inherently blind,which makes the search inefficient and unscalable.Gnutella is a typical flooding protocol.Methods based on DHT are efficient and scalable. Plaxto,Tapstry,Pastry,CAN,Chord are all excellent represents of methods based on DHT. Chord is a structured P2P of circle topology. As it has the neat structure and better scalability, Chord is used widely。This paper presents a new Chord algorithm by extending the finger table on the basis of deep analyses of Chord,this algorithm makes improvements in the following two aspects:(1)Finger table is changed into order-four. This increases the density of fingers and the probability of finding destination node。(2) This algorithm adds a R_Finger table.This makes Chord search in two directions.R_Finger is a reverse of finger table.So Chord can choose next-hop node in clockwise and anticlockwise directions.So this algorithm can approach the destination node faster.This algorithm combines the advantages of order-four Chord and dual Chord,so Chord can achieve the bidirectional search by the distance between the key words and the alternate node. This algorithm has lower latency and shorter search path than Chord. At last simulation results indicate that the algorithm inherits the advantages of Chord,such as simplicity,efficiency,reliability,load balance and low cost.So this algorighm gets higher search efficiency than original Chord.This paper,using XML technology,presents a P2P file sharing system-PPShare, which supports exact-match lookup and fuzzy search simultaneously.