Enhancing Tit-for-Tat Strategy to Cope with Free-Riding in Unreliable P2P Networks

P2P applications suffer from free-riding. In economics terminology, free-riding is the rational behavior of the participants. So it´s feasible to use game theory to analyze this problem and design countermeasures. Tit-For-Tat is a simple and efficient equilibrium strategy in repeated game environments. In this paper, we construct a game model in P2P environments and deduce the constraint under which the strict tit-for-tat is an equilibrium strategy. We then improve and adapt the tit-for-tat strategy to the dynamic property in P2P networks, and deduce the constraint under which it is still an equilibrium strategy. Finally we study through simulations the performance improvement of the enhanced tit-for-tat and give suggestion of how to choose proper system parameters under different network conditions.