Bt Simulator Design And Protocol Optimization In Ppcdn Applications

For the appearance and prevalence of new applications such as streaming media, we need to solve the outstanding problem of how to meet the high demand and heavy consumption of network resources. So we need a high performance content distribution system to use its resources efficiently. PPCDN comes to birth. PPCDN is a supporting system of IPv6 stream distribution application system as well as a content distribution system based on P2P technology, sponsored by research of the IPv6 based next generation internet key technology and industrialization promotion of Beijing Municipal Science and Technology Commission. It is much difficult to research and optimize a P2P system because of its open and dynamic nature. As one subject of PPCDN, this thesis takes on the work of system protocol optimization.The author proposes a generic structure of P2P simulator after examining the fundamental P2P theory and other P2P simulators carefully. Based on the generic structure, the author develops a BT protocol simulator and gives its program structure and implementation details. Finally, the protocol optimization work is accomplished with the help of the BT simulator.The BT simulator is developed in C++ language using the modularization idea. It consists of four parts: the discrete event-driven module, the topology module, the protocol module and the input-output module. The discrete event-driven module is the heart of the simulator. It sorts and schedules all kinds of events effectively and all other modules are running on it. The topology module uses the GT-ITM network topology and flow model, and drives the whole system. The protocol module simulates the BT protocol, including the construction of the BT overlay network and the message description of BT protocol. The input-output module reads the configure files and outputs the outcomes.The author has optimized the PPCDN system with the support of the BT simulator. Firstly, the author has proved the importance of the punishment and incentive mechanism to the BT system and proposed some improvement of its Unchoke Algorithm. Secondly, the author has examined the system's steady state as well as the seed's pressure and optimized the ESP's service strategy. In order to verify the research work, the author has carried out a lot of experiments. The results have shown the effectiveness of the optimization work.