An analysis of peer-to-peer networks with altruistic peers

We develop a new model of the interaction of rational peers in a Peer-to-Peer (P2P) network that has at its heart altruism, an intrinsic parameter reflecting peers’ inherent willingness to contribute. Two different approaches for modelling altruistic behavior and its attendant benefit are introduced. With either approach, we use Game Theoretic analysis to calculate Nash equilibria and predict peer behavior in terms of individual contribution. We consider the cases of P2P networks of peers that (i) have homogeneous altruism levels or (ii) have heterogeneous altruism levels, but with known probability distributions. We find that, under the effects of altruism, a substantial fraction of peers will contribute when altruism levels are within certain intervals, even though no incentive mechanism is used. Our results corroborate empirical evidence of large P2P networks surviving or even flourishing without or with barely functioning incentive mechanisms. We also enhance the model with a simple but powerful incentive scheme to limit free-riding and increase contribution to the network, and show that the particular incentive scheme on networks with altruistic peers achieves its goal.

Vasilis VassalosEmail: URL: http://wim.aueb.gr/vassalos

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Dimitrios K. Vassilakis   2005–today: PhD candidate in the Informatics Department of the Athens University of Economics and Business (AUEB). Research areas: Operations Research (OR), Game Theory, economic models and applications of Game Theory on the internet (anti-spam, P2P networks), applications of OR on electricity scheduling. Vasilis Vassalos   2003–today: Assistant Professor in the Informatics Department of the Athens University of Economics and Business (AUEB). 1999–2003: assistant professor in the Information Systems Group of Information, Operations and Management Sciences (IOMS) Department in the Stern School of Business at New York University. Research areas: databases, Web-based information systems and middleware development, generation of user interfaces and Web services for semistructured data sources, integration of mobile data sources, XML query processing, digital libraries.