Mobility Based Checkpointing And Trust Based Recovery In Manet

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Proposed work is a mobility based checkpointing and trust based rollback recovery algorithm to provide fault tolerance in Mobile Ad hoc Network (MANET). Here each mobile host maintains a count of number of clusters a mobile host traverses through, during a single checkpoint interval. A mobile host increments ‘cluster-change-count’ by 1, each time it leaves a cluster and joins another. Each mobile host saves a checkpoint independently if its ‘cluster-change-count’ exceeds a predefined threshold. This measure is important because each mobile host leaves its last checkpoint and logs at different clusters that it has visited earlier. If the mobile host fails, the time to search and collect its last checkpoint and logs gets added to the recovery time of the mobile host. In MANET, retrieval of checkpoint and logs has to be done through a number of intermediate mobile hosts because each mobile host has short area coverage, hence direct communication among distant mobile hosts is not possible. Now if any of these mobile hosts fail, depending on the nature of failure, the checkpoint or log may be lost or forwarding of them to the failed host may be delayed causing unsuccessful or delayed recovery of the failed host respectively. This can be avoided if it is ensured that the checkpoints and logs are forwarded only through trusted nodes. Trust model proposed here computes trust value of a mobile host based on four factors: failure rate, availability in network, unused energy and recommendations from neighbour mobile hosts. Simulation results show that proposed algorithm achieves low recovery cost and high recovery probability of failed mobile hosts.