| As one of the Real-World Applications, Peer-to-peer (p2p) network is playing a more and more meaningful role in people's day-to-day Internet life. With the generation of p2p, certain inherent flaws of traditional Client/Server model, such as server bottleneck and single point failure, have turned out to be solved to a comparatively high degree. However, since p2p is just in its preliminary stage, lots of problems still do exist and require further research. Peer-to-peer research covers different fields such as network architecture, query algorithm, resource management, and security. As for a system design, network topology is the first essential to be determined, i.e. choosing the appropriate network architecture is the fundament of all the operation and application of a system. Napster, the most popular p2p network in the nineties of the twentieth century, uses centralized network architecture, i.e. system accommodates shared resource list, online node list and resource querying service to all users through its central server. As a result, according to central server's assistance, nodes in Napster can establish connections and finally swap MP3s. However, the same as traditional Client/Server system, single point failure threats Napster network. Once Napster server fails, all nodes are incapable of reaching other nodes through Napster network. Accordingly, the whole system would fail to accommodate services. Gnutella network which was generated after Napster, completely abandons central system server and uses purely distributed architecture. Nodes-searching in Gnutella proceeds by flooding queries to all nodes within a certain search horizon, rather than through server's assistance. Because all nodes are absolutely equal, the breakdown of a few nodes won't observably impact the whole system. Therefore, Gnutella eliminates the threat of single point failure from the root of the problem. But, the issue for Gnutella network itself is the lack of effective way for its node to acquire other peers'information. Accordingly, the consequences are: the operation of Gnutella network is conducted in a disordered way; network bandwidth is usually taken by a huge amount of broadcasting data; the lack of trust between nodes and communication security; frequent network package drop and so on. This paper comes up with a new regional p2p system which is similar to people's true life by means of combining the advantages of both Napster and Gnutella networks. Although, threats of single point failure inhere in Napster's server-assisting architecture, never exists any problem for its node to find other peers, neither will the system generate exponentially expanding broadcasting data in network. Meanwhile, the existence of central server makes it easier to solve security and reputation issues according to the application of effective measurements. Gnutella is established on the base that all nodes'in Gnutella are absolutely equal. Thus, it radically eliminates the server bottleneck by abandoning servers at all, however, neglecting the importance of system management. Extreme distribution leads to anarchy of the whole system. Mischievous nodes can easily cheat healthy nodes to destroy the whole system. In fact, interests and habits of every node in a system form the whole system's character. Research reveals that Gnutella network bears the Power Law and Locality of content serving, i.e. only a few nodes in the network have a high degree of connectivity while all the others have a very low degree of connectivity, according to which Gnutella network is virtually divided into different clusters. By the same way as a society comes into being, nodes in Gnutella system gradually come into relatively stable colonies. And most of their activities are within certain areas. Although the peer to peer relationship among nodes still exists globally, it indeed takes effect in a compact and effective way within every colony, i.e. within each cluster. According to Napster and Gnutella's identities stated above and considering real world circumstances, this paper detailed analyses and compares different p2psystems'advantages and shortcomings, as a result, proposes a regional p2p model named ReXcel. ReXcel divides the whole network into separate regions architecturally, based on the fact that Gnutella's distributed p2p network would finally come into different clusters. In each region, one super node (server) would be set up, which accommodates online information service and partial directory querying service to local nodes. These nodes would establish connections for data swap with the assistance of the super node. Nodes in a certain region can directly or indirectly communicate with nodes in other regions. All regional servers build up a globally purely-distributed p2p network. Web Service is a new idea of component model for building up distributed applications. It is a Service Oriented Architecture (SOA). The relationship between nodes in p2p systems is just the same as it is between service providers and service requesters. Thus, ReXcel uses Web Service as its communication framework. On one hand ReXcel uses XML to encapsulate the data transported through the network, on the other hand it bases its communication on HTTP. Together with the regional server management, ReXcel solves the security issues and firewall-crossing problem soundly. Both regional servers and ordinary nodes providing all their operations such as searching, resource downloading through Web Services...
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