A reputation based incentive mechanism for selfish BitTorrent system

The current BitTorrent-like file sharing systems suffer from peer selfish behaviors. The uncooperative peers can freeload compliant users by free-riding and exploiting. To study the performance of BitTorrent´s embedded incentive mechanism against selfishness, a fluid model with three different classes of peers, namely normal peers, exploiters and free-riders, is established. We point out that the current BitTorrent system can not provide an effectively differentiated service in accordance with contribution of peers. Therefore, a reputation based incentive (RBI) mechanism for selfish BitTorrent system is proposed. RBI defines a trust value for each peer associative to its historical performance to the whole system. With the trust value, the choking mechanism is modified to ensure the more trustworthy peers will have more chances to get served. Our simulation study indicates that RBI mechanism can remarkably prevent exploiting behaviors, severely penalize free-riders, and thus result in a fairer allocation of bandwidth among peers.