The effect of direct interactions on reputation based schemes in mobile ad hoc networks

In multihop networks such as mobile ad hoc networks selfish or misbehaving nodes can degrade network performance. Reputation based models have been developed to enforce cooperation and to discourage node misbehaviour. These schemes detect and isolate selfish nodes and maintain network throughput by enabling nodes to construct paths that only include good nodes. In order to punish selfish nodes and restrict their services, selfish nodes are not provided with packet forwarding services anymore by the good nodes in the network; however they can still gain throughput or utility by interacting directly with the destination nodes. The commonly adopted simulation parameters used by the research community for the evaluation of reputation based schemes in mobile environments usually produces high direct interactions. These direct interactions result in noticeably higher throughput and node utility for the network overall causing confusion: these metrics are increased or decreased due to the direct interactions or due to the reputation based scheme. We implemented the popular CONFIDANT reputation-based scheme to confirm how much throughput is the result of these direct interactions. Our simulation studies show that in the presence of 20% selfish nodes and in a continuous mobile environment, 59% of the evil throughput and 29% of the good throughput was gained through direct interactions among nodes. These direct interactions accordingly affect delay and routing overhead in the network.