Higher Order Chord: A New Policy Of Resource Searching In Peer-to-Peer Networks

Peer-to-peer network is becoming a hot topic dramatically in recent years. Various applications are developed base on it. Peer-to-peer network can provide unlimited storage and network bandwidth, which is unthinkable in traditional centralized server. The nodes in peer-to-peer network work as both service provider and consumer. Nodes cooperate and share resources with a totally distributed and symmetric algorithm. Hereby the core of the networks'application is moved from central server to those terminal devices distributed in the edge of network. Currently web sites are the core of Internet. Peer-to-peer is going to change this completely. People will be able to involved in network activity in a much more initiative way. From Client/Server model to Peer-to-peer model, the sharing in Internet is going into a whole new level. This is a great opportunity to solve many unsolved problems, and have bright future in distributed computing, cooperative working, search engine, file sharing and so on. The most critical problem in peer-to-peer network is how to search resources in a decentralized way while provide efficiency, security and scalability. We can divide all existing search method into two categories: Flooding and DHT (Distributed Hash Table) based. Gnutella is a typical flooding protocol. But it is proved to be unscalable in practice. Although many efforts were devoted to control the broadcast package in flooding algorithm, it is very hard to limit the exponential growth of overhead lead by increasing of users. So, many study turns to DHT. Plaxton, Tapstry, Pastry, CAN, Chord are all excellent represents of them. Chord is featured with its high performance in continuous changing network, which is vital in most peer-to-peer environment. This paper presents the concept of "order"in Chord. Figure out that original Chord can be regard as order-2 Chord. Higher order Chord will relay search request to distinct node faster, in cost of bigger route table need be maintained in every node. In order to verify the performance of higher order Chord, a program was made based on p2psim to simulate higher order Chord. The simulation result shows that higher order Chord do bring better performance than original Chord.