The Research On Searching Mechanism In Chord Networks

With the rapid growth of Internet and computing power, Peer-to-Peer(P2P) networks have become a hotspot in researching field of computer networks.P2P networks share idle CPU power,free disk space and network bandwidth between different nodes in a distributed and equal way.The nodes in P2P networks work as both service provider and consumer.From Client/Server model to P2P model,the sharing in Internet is going into a whole new level.P2P networks have bright future in distributed computing,cooperative working,search engine,file sharing and so on.The effectiveness of a P2P network largely depends on the versatility and scalability of its searching mechanism.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. Plaxton,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 DOTChord 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-three.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-three 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 DOTChord 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.