Incentive Mechanism Study Of Bittorrent Protocol Based On CPN

BitTorrent is one of the most popular file sharing protocol, as one of the main applications of P2P technology, over the years has achieved great success. Incentives plays a crucial role in BitTorrent, it motivates users to upload more resources so that they can obtain shorter download time. However, recent work has found that BitTorrent suffers from the free-riding induced by selfish peers, that is, peers consume much more resources but make little contribution to the system. As a result, the effect of original incentive mechanism and the system robustness has been widely questioned.In this thesis, we make a detailed analysis to the incentives built into the BitTorrent protocol and found that original incentive mechanism is really easy to induce free-riding. In order to provide a better motivate to peers to avoid free-riding, we propose a new, more effective incentive strategy. And, we also make an evaluation to the effect of the incentive strategy. First, a formal model of BitTorrent protocol based on CPN is given, which first contains a larger number of participants, allows us to make a more accurate evaluation to the performance of BT protocol’s implementation. Then, we verify the correctness of the model from local and whole by the simulation execution and state space techniques of the CPN tool. At last, we make a performance analysis to the model which is verified the correctness, the analysis results show new incentive mechanism is more effective in motivating the participants contribute resources while punishing the free-rider, of course, will also make the system more robust in the long run.