Based On The Design And Realization Of The Oversim P2p Simulation Systems

With the prompt development of information technology, P2P (Peer-to-Peer) technology has gradually become the focus of researches and attentions.Because of its unique self-organization and distribution, it's developing rapidly on the Internet, and it has become an integral part of the Internet network. The research of P2P technology involves many aspects, including content distribution, caching data resources, grid computing, distributed computing, data deployment, self-organizing networks and so on.In the filed of research about P2P technology, incentives mechanism, direct traffic and other algorithms have caused people's concerns, but the performance testings of these algorithms are lack of an effective platform. Therefore it has become a good choice to use simulation software in the limitied circumstances. Because of this, the pa-per presents a simulation system based on OverSim of P2P.OverSim is based on OMNET++ (a C++ open source emulator) and it is the over-lay network simulation framework, using discrete event simulation to simulate the net-work of message exchange and process. In this paper, the system, which is designed and implementationed, is a typical unstructured P2P model, and it uses the BitTorrent pro-tocol to simulate P2P system sharing files. The Tracker Server responses to Peer's download request in the form of peerlist to notify the whereabouts of the corresponding peer to peer download. File sharing function in the simulation, the system do peer selec-tion, piece selection and download blocking algorithm based on the BT protocol. Through large-scale network simulation it verified the oerformance of the system. In the download time, network size and the robust of the system can be guaranteed.This paper first describes the component of the P2P system and the related techni-cal background, then designs the simulation system based on the framework of OverSim, starts from the basic module design and message-passing process, completes the com-plex design of the Tracker Server and the Client Host, and then uses C + + code ini file configuration to complete the simulation system .In the process of running, the genera-tion of the node havs to rely on Churn generator to achieve. The number of nodes is dynamically configurable, this ensures the scale of the simulation network.The system is not perfect in some respects, just did some research on P2P system based on BT pro-tocol, and did not consider more complex scenarios, including adding credit mechanism to ensure the incentives and so on. About the latter part of the work, mainly in the fol-lowing aspects: First, adding incentives to achieve fairness; second, allocate the download bandwidth in order to ensure better efficiency, third, add different domains to achieve inter-domain traffic control, simulate the real environment, in order to achieve the purpose of network traffic optimization.