Discovering Free-Riders Before Trading: A Simple Approach

Free-riding is one of the most serious problems encountered in Peer-to-peer (P2P) systems like Bit Torrent. Incentive mechanisms, including those based on reputation have been proposed to deal with this problem, but are still not effective in preventing free-riders from completing a download. This is because they discover the free-riders´ behavior during or after the process of trading, giving free-riders the opportunity to download from others. In this paper, we propose PreDiscover, a novel approach to prevent free-riding behavior in Bit Torrent. In PreDiscover, regular peers and free-riders can be recognized before trading. So free-riders have little opportunity to download blocks from others. Our simulation results indicate that this new mechanism is very effective in discouraging free-riders and foster fairness.