Mitigating routing vulnerabilities in ad hoc networks using reputations

Nodes in mobile ad hoc networks have limited transmission ranges that necessitate multihop communication. Hence the nodes expect their neighbours to relay the packets meant for nodes out of the transmission range of the source. Ad hoc networks are based on the fundamental assumption that if a node promises to relay a packet, it will relay the packet and will not cheat. This assumption becomes invalid when the nodes in the network have contradictory goals. As a result, routing protocols for ad hoc networks become vulnerable to rogue nodes. The reputations of the intermediate nodes, based on their past history of relaying packets, can be used by their neighbours to ensure that the packet will be relayed by the intermediate nodes. This paper introduces a reputation scheme for ad hoc networks that can motivate the intermediate nodes to relay packets. The source performs a route discovery (using Ad hoc on Demand Distance Vector Routing Protocol (AODV)) and finds a set of routes to the destination. Instead of choosing the shortest route to the destination, the source node chooses a path whose next hop node has the highest reputation. This policy, when used recursively, in the presence of 40% rogue nodes, improves the throughput of the system to 65%, from the 22% throughput provided by AODV with same number of rogue nodes. This improvement is obtained at the cost of a higher number of route discoveries with a minimal increase in the average hop length. Mitigating routing vulnerabilities in ad hoc networks using reputations 151