A Distributed and MeasurementBased Framework Against Free Riding

Peer-to-peer networks have attracted a signicant amount of interest as a popular and successful alterna-tive to traditional client-server networks for resource sharing and content distribution. However, the exis-tence of high degrees of free riding may be an impor-tant threat against P2P networks. In this paper 1, we propose a distributed and measurement-based method to reduce the degree of free riding in P2P networks. We primarily focus on developing schemes to locate free riders and on determining policies that can be used to take actions against them. We propose a model in which each peer monitors its neighboring peers, makes decisions if they exhibit any kind of free-riding, and takes appropriate actions if required. We specify three types of free riding and their symptoms observable from the activities of the neighboring peers. We employ sim-ple formulas to determine if a peer exhibits any kind of free riding. The counter actions to be applied to the free riders are dened. We combine the mechanisms proposed to detect free riders and to take appropriate actions in an ECA rule and a state diagram.