Conventional routing protocols in Mobile Ad-hoc Networks (MANETs) incur high control overhead for flooding during route discovery since network topology frequently changes due to node mobility. In this paper, an Encounter-based Selective Forwarding Scheme (ESFS) in which every node in the network maintains a routing table containing its latest encounter information with other nodes, is proposed to reduce route discovery control overhead. In the route discovery process, instead of flooding with route request messages, an intermediate node searches for the nodes among its neighbors that have encountered the destination more recently than itself. Also, instead of forwarding route requests to all candidates, the intermediate nodes choose and forward route requests only to two or three earlier responders. Therefore, ESFS can exclude considerably a number of unnecessary nodes participating in a conventional route discovery phase. Simulation results show that ESFS can save 78% and 29% of control overhead messages during route discovery compared to AODV and FRESH.
