Abstract—The performance of peer-to-peer systems dependson the level of cooperation of the system’s participants.While most existing peer-to-peer architectures have assumedthat users are generally cooperative, there is great evidencefrom widely deployed systems suggesting the opposite. Todate, many schemes have been proposed to alleviate thisproblem. However, the majority of these schemes are eithertoo complex to use in practice, or do not provide strongenough incentives for cooperation.In this work we propose a scheme based on the generalidea that offering uploads brings revenue to a user, andperforming downloads has a cost. We also introduce atheoretical model that predicts the performance of thesystem and computes the values of the scheme’s parametersthat achieve a desired performance. Our scheme is quitesimple and very easy to implement. At the same time, itprovides very strong incentives for cooperation and improvesthe performance of P2P networks significantly. In particular,theory and realistic simulations show that it reduces thequery response times and file download delays by one orderof magnitude, and doubles the system’s throughput.

Keywords: P2P networks, user cooperation, theoreticalanalysis, realistic simulations.

Cite: Wei-Cherng Liao, Fragkiskos Papadopoulos, Konstantinos Psounis, "A Peer-to-Peer Cooperation Enhancement Scheme and its Performance Analysis," Journal of Communications, vol. 1, no. 7, pp. 24-35, 2006.