P. Antoniadis (Department of Computer Science, Athens University of Economics and Business)
C. Courcoubetis (Department of Computer Science, Athens University of Economics and Business)
R. Weber (Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WB, UK)
In Second Workshop on the Economics of Peer-to-Peer Systems, Harvard University.
Paper [pdf - 174KB]
Presentation [pdf - 92KB]
The asymptotic analysis of certain public good models for p2p systems suggests that when the aim is to maximize social welfare a fixed contribution scheme in terms of the number of files shared can be asymptotically optimal as the number of participants n grows to infinity. Such a simple scheme eliminates free riding, is incentive compatible and obtains a value of social welfare that is within o(n) of that obtained by the second-best policy of the corresponding mechanism design formulation of the problem. We extend our model to account for file popularity, and discuss properties of the resulting equilibria. The fact that a simple optimization problem can be used to closely approximate the solution of the exact model (which is in most cases practically intractable both analytically and computationally), is of great importance for studying several interesting aspects of the system. We consider the evolution of the system to equilibrium in its early life, when both peers and the system planner are still learning about system parameters. We also analyse the case of group formation when peers belong to different classes (such as DSL and dial-up users), and it may be to their advantage to form distinct groups instead of a larger single group, or form such a larger group but avoid disclosing their class. We finally discuss the game that occurs when peers know that a fixed fee will be used, but the distribution of their valuations is unknown to the system designer. We also analyse the case of group formation and discuss the game that occurs when peers know that a fixed fee will be used, but the distribution of their valuations is unknown to the system designer.
Keywords: economics, p2p networks, public goods, incomplete information, incentives, mechanism design, asymptotics