Overcoming misbehavior in mobile ad hoc networks: an overview

In the recent years, wireless networks have experienced an enormous growth which has given rise to new research challenges. Ad hoc networks are composed of autonomous nodes that are independent of any fixed infrastructure. Mobile ad hoc networks have a fully decentralized topology and they are dynamically changing. Besides these challenges, the wireless transmission medium introduces limitations in communication. For these reasons, providing security guarantees is particularly difficult. In a mobile ad hoc network every node acts as a router for its neighbors. The routing protocols that have been proposed assume that the nodes will fully participate. Unfortunately, node misbehavior is a common phenomenon. Misbehavior is due to selfish or malicious reasons. Another reason, which is rarer, is a faulty link due to the wireless medium. Misbehavior can take place at all layers. At the Physical layer a misbehaving node can increase its transmitting power, adversely affecting the network performance. At the MAC (Medium Access Control) layer a node may choose to avoid waiting for its turn to access the medium, taking an unfair advantage of the shared medium. The basic threat at the Network layer is the non-cooperative behavior as far as packet forwarding is concerned. The proper execution of a routing protocol demands that the intermediate nodes in a path forward the packets correctly to the intended receivers. Misbehaving nodes do not forward these packets. A routing protocol for MANETs should give incentives for cooperative action or at least it should be able to detect misbehaving nodes and correct them.