Research On Propagation Model Based P2P-VoIP Interception System

With the rapid development of P2P technology, P2P technology is increasingly concerned about applications in the field of communication. P2P-VoIP system is a typical application. P2P-VoIP system has lower deployment costs and breaks through the bottleneck of the C/S mode. But because of the openness of P2P-VoIP network, the expansion of call signaling and the distribution of data transmission, there is a great challenge on the security of network information.The difficulty of the P2P-VoIP network interception is first analyzed, as well as the status of current researches on the issue, and then characteristics of the application based on the propagation model is in-depth studied. Combined with the advantages of P2P technology, a intercepting system based on the model is presented.The framework of the P2P-VoIP interception system is designed, according to the characteristics of the application based on the propagation model. And various components of the framework are described in detail on their functions. Further more, the module structures and interfaces between the modules are defined. In order to strengthen the scalability and robustness of the interception system, interception agents are organized in a P2P network. The different forms of organization are introduced.In order to manage the system simply, a lightweight protocol stack is designed for management of interception agents and communication between agents. In line with the protocol a set of basic instrucion of interception is defined, and some special management methods are made out. A specific deployment process of the interception system is given in accord with the system framework. Then the application of the interception system is described. According to the agent deployment on the intercepted user host, there are different interception methods.Before the interception system starts to work, the interception agents must be deployed. Therefore, a simulation on the deployment of the system is designed, include designing the architecture and corresponding algorithms. Choosing different propagation algorithms, and setting different nerwork sizes and propagation conditions, make a large number of simulation results. After analyzing the simulation results, some factors which impact the time-cost of the deployment are found out, like PSN (Propagation Start Number) and EDR (Effective Detection Rate).In the research on the time-cost of the system deployment, some shortcomings of the hybrid propagation algorithm are discovered. One of them is that the hybrid algorithm would reduce the efficiency of the deployment though it would save time-cost. After the further study on the passive propagation algorithm, we find that the passive algorithm would cover each node 6 times statistically in despite of network sizes and propagation conditions. It means when detecting a certain number of nodes which have been more than 6 times covered, the deployment of the system will finish. Based on the conclusion, an improved hybrid propagation algorithm is designed to improve the efficiency of the deployment.