Performance of peer-to-peer resource sharing networks depends upon the level of cooperation of the participants. To date, cash-based systems have seemed too complex, while lighter-weight credit mechanisms have not provided strong incentives. We propose exchange-based mechanisms for providing incentives for cooperation in peer-to-peer file sharing networks. Peers give higher service priority to requests from peers that can provide a simultaneous and symmetric service in return. We generalize this approach to n-way exchanges among rings of peers and present a search algorithm for locating such rings. We have used simulation to analyze the effect of exchanges on performance. Our results show that exchange-based mechanisms can provide strong incentives for sharing, offering significant improvements in service times for sharing users compared to free-riders, without the problems and complexity of cash- or credit-based systems.