A MAC Protocol Based On Reputation Mechanism Of Ad Hoc Network

Self-organized network is also called Ad Hoc network. Its characteristics such as open medium, dynamic topology and distributed cooperation not only make it easy to organize a network, but also bring a lot of security problems to it. MAC layer is mainly responsible for nodes' accessment to the medium, and the security in MAC layer is also an important part of security in Ad Hoc networks.A MAC protocol based on reputation mechanism of Ad Hoc network is proposed in this thesis. Under the new protocol, every node in the network estimates its neighbors' reputation to ensure that attacking nodes' reputation value will be decreased and good nodes' reputation value will be increased. Each node in the network owns a token which has limited period of validity and manages tokens by the help of reputation. A node can communicate only when its token is valid. To prolong the period of validity, a node has to apply to its neighbors, if the node's reputation value is low, its token's period of validity won't be prolonged. So attacking nodes will be isolated out of the network and good nodes can own tokens with long period of validity. By this way attacking nodes can be punished and good nodes can be encouraged and fair accessment can be protected. Nodes with valid tokens can share the channel under IEEE802.11 DCF to protect the safe and fairness of media accessment.The validity of the new protocol is simulated through NS network simulation software in four conditions which include without attacking nodes under 802.11, without attacking nodes under new protocol, with attacking nodes under 802.11, with attacking nodes under new protocol. Simulation result shows that in the condition without attacking nodes, the network has less throughput under the new protocol than under 802.11 because of the new protocol's bigger overhead, but the difference is not very evident. In the condition with attacking nodes, attacking nodes' throughput will be limited evidently and good nodes will be protected effectedly under the new protocol.