Opportunistic rollback recovery in Mobile Ad hoc networks

Mobile Ad hoc networks (MANETs) have significantly enhanced the wireless networks as they eliminate the need for fixed infrastructure and are easily deployable. Apart from their application for communication purposes, these are increasingly being used for expanding the computing capabilities of existing cellular mobile systems and for the implementation of mobile computing grids. Therefore, a fault tolerance technique is crucial in order to effectively utilize the computing potential of the network. Rollback recovery has been widely used to achieve fault tolerance in distributed networks; yet its application is not trivial in a MANET due to limited availability of stable storage, node mobility and frequent network partitioning. The paper presents a rollback recovery protocol for MANETs which addresses these challenges by using opportunistic routing. Since all nodes may not have enough stable storage, the nodes with sufficient availability of stable storage are distinguished as Checkpoint Storage Nodes (CSNs). Opportunistic contacts between mobile nodes are used, firstly, for locating Checkpoint Storage Nodes in the network and subsequently, for retrieving the last saved checkpoint of a failed node from a CSN at the time of recovery. We calculate the recoverability, i.e., the probability that a process can recovery in a given time period.