| Since the popularity of Napster starting from 1999, the research on P2P technology has caused more and more attention. During recent years, P2P technology has developed so quickly that it's listed in the four new technologies which will change the future of the Internet by Fortune.P2P technology has solved the single point of failure and accessing hot spot problems of traditional C/S model. It can defend DoS attack effectively and propose good solutions aiming at balancing net flow, using clients' source effectively, eternal storage and so on.In the P2P network, each computer performs as both server and client, which means it request service and offer service as well. It has many characteristics of decentralization, self-organization and such like Thus, the core of the whole Internet's network application has transferred from central server to terminal device on net edge. People can take part in net activities more initiatively, which realizes the freedom and equality principle of the Internet. Meanwhile the utilization of sources like information and band width is improved. The sharing on the Internet has been developed to a higher level.The key technique of P2P is to build what we called overlay network above the physical network, which offers the service of source discovery and orientation. Overlay network is a logical network. And it can be separated in two types, one is non-structured network based on flooding algorithm, and Gnutella as representative, the other is structured network based on distributed hash-table (DHT), and Chord and Kademlia as representatives. When the size of network grows, the sent message by flooding algorithm is exponent growing, which can cause the net storm easily. So recently the researches concentrate on methods based on DHT.In this paper we emphasize on Chord and Kademlia's protocol based on DHT, research on the principles of so pop softwares like BT and eMule, analyze the basic platform JXTA of P2P system deeply, even comprehend the thoughts of layer and super-peer in the JXTA detailed, and based on the above proposes a new kind of source discovery model--RCDHT.RCDHT is on the base of Kademlia protocol, aiming at heterogeneity of network nodes' capability and considering network proximity of nodes, and is improved from the following three points:? Aiming at node's heterogeneity, improve the Kademlia model, optimize k-bucket mechanism's information storage and parameter setting especially; nodes with high integration can store more rout information and offer more service, eliminate probability of system bottleneck caused by weak nodes.? Aiming at network proximity of nodes, introduce the concept of time-stamp, which helps consider physical network proximity when distributing node's ID, in this way nodes which have close physical distance can have related closer node logical distance.? To organize and manage the net better, the whole P2P net is divided into two layers: the main net and the branch net. The main net uses improved Kademlia protocol, while the branch net uses topology to have complementary advantages and a good combination.In the end, to validate the performance of RCDHT in real network environment in which nodes change continually, P2PSim simulator by MIT is used to simulate model and compare performance. The results show that RCDHT can advance the system's performance.At present, there are many applications based on P2P, for example, Skype, BT, eMule, Groove and so on, which are related to various fields such as distributed computing, file sharing, communication and collaboration, platform and so on. We firmly believe that P2P is not only a meaningful research field, but also a potential business market. P2P technology will have a brighter future!... |
PDF Full Text Request