Research On Several Vital Problems Of Peer-to-peer Network

In recent years, P2P network has been a research hotspot in the domain of network and communications, and is deemed as one of four basic technologies in next generation network architecture. Because the following several problems directly decide the usability and system efficiency of P2P network, they have been studied for theoretic significance and applied value.1. P2P network is essentially a distributing overlay network based on Internet. The goal of P2P network is to construct large-scale cooperating and resource-sharing by making full use of every possible end-system in internet-scale. The topology structure of P2P overlay network decides its system performance, better topology structure makes the goal more easily achieved.2. The basic assumption of P2P network is that peers are willing to share resources with others.However, because of peers'heterogeneity, the rational users of P2P network are self-determination.The object of them is to maximize the personal utility without considering the whole network productivity.Besides, there still exist a large amount of P2P services with unreliable qualities and malicious actions. One way to solve these problems is to introduce trust model and incentive mechanisms to ensure data credibility, encourage effective cooperation between nodes and rationally use network resources.3. Currently, file-sharing is the most widely applications of P2P network. Thus, research on the behaviors of P2P file sharing systems can contribute to a deeper understanding the features of P2P file sharing systems, have a positive significance for reasonable and effective management and control to network traffic as well as enhance P2P file sharing system performance, stability and scalability.The thesis focuses on these problems, and makes the main research subjects and contributions as follows:1. Owing to P2P overlay network models don't taking clustering and symmetry of P2P network into account,this paper proposes a a novel P2P overlay network model based on the algebra and graph theory method of Cayley graph. Its simplicity and symmetry can ensure the self-organization and scalability of P2P network. Besides, comparing to the existing P2P Overlay Network models, this model provides better robustness, higher enquiry efficiency and better load balance. Furthermore, it possesses the property of high clustering.2. Due to the sacrifice of peer anonymity and information flooding in most current trust models, an anonymous peer-to-peer trust model was proposed in this paper, which comes from construction approach of trust relations in the social network, in which, a peer's trust value was calculated according to two aspects. The result of using several public/ private key pairs and onion routing is that this model is capable of commendably guaranteeing peer anonymity and data authenticity.Based on this trust model, this paper presents a novel topology structure and resource search mechanism, in which, the capability of serving is depicted by the trust value of peer, links based on trust constructs the dynamic topology of network, and the resource search mechanism is introduced based on this dynamic topology. So, it improves the search performance of the network.3. Based on the assumption that peers in P2P network are rational and selfish, an incentive mechanism for P2P network was proposed in this paper, which comes from limitless repeated game theory. This paper also implemented the finite state machine of the incentive mechanism. Punishing mechanisms to selfish peers and some essential norms are introduced in this model so that rational peers are stimulated to maximize their own utility and contribute their free resource, which in turn improve the whole utility of the system.4. By analyzing the characteristics of P2P file-sharing system, with the conformation method of the dynamic model SEIR for infectious diseases, this paper proposes a file-propagation model of P2P file-sharing system, in which, most states of peers are adequately taken into account in the model. Simultaneously, the basic reproduction ratio of file-propagation is expressed based on the model, which shows the effect of several factors on the speed of file-propagation, so that it can be used as the reference for the index to improve the speed of file-propagation and the utilization rate of the file-sharing system..