| With the wide popularity of the Internet and the continual growth of computer users, as well as the persistent advancement of the network bandwidth and computer processing power, peer-to-peer (P2P) network is rapidly developed. It provides a variety of ways to attain information and services, and observably improves the level of collaboration. In recent years many structures of P2P have been presented. The P2P network mainly includes two forms: Unstructured P2P network and Structured P2P network. The latter, based on Distributed Hash Table, because of its high querying efficiency and expansibility, has aroused people's great attention.How to locate resource nodes efficiently and quickly in P2P network is the kernel question. This paper firstly analyses the routing algorithms of structured P2P network, such as pastry, Tapestry, CAN and Chord, especially Chord and other advanced algorithms based on Chord. Then, based on the analysis above, a new routing algorithm—Chord based on Multi-ring (MR-Chord) is brought forward. MR-Chord uses a structure combined with multi-ring and group.Each node in one group records all routing information of the group, and all groups link into multiple rings with recursive algorithm. This sturcture can increase the number of online nodes and reduce redundancy of the routing table. Analysis in theory and simulation results shows that MR-Chord can improve the performance and adaptability, and the routing tables have few redundancies.Finally, in order to validate the actual performance of MR-Chord in the factual network, this paper designs and realizes an instant messaging system based on MR-Chord. In allusion to the overloading weakness of traditional instant messaging system servers, the MRC-IM uses the MR-Chord structure, and lightens the load on the server, so that it can be directly applied to ordinary Web server. And in accordance with the characteristics of MR-Chord, it has new functions, such as anonymous login and a group chat.The main work and innovation of this paper are: research of the structure of P2P network; detailed analysis of the Chord algorithm and its related algorithms; design of MR-Chord based on multi-ring; design and realization of an instant messaging system based on MR-Chord. |
