Efficient flooding using prefetching in on-demand routing protocols for mobile ad-hoc networks

In this paper, we propose an enhancement technique for dynamic source routing protocol (DSR) using prefetching of frequently used routes in the cache. DSR is a popular on-demand reactive routing protocol in mobile ad-hoc networks (MANETs) which uses flooding for route discovery and route maintenance only when a node has data that needs to be transmitted. Flooding causes serious redundancy, contention and collision in the network which increases the overhead of transmission in a dynamic network where the nodes have different mobilities. Most of the research work on prefetching has focused on using this technique for improving data access in clustered networks; but this involves a lot of overhead in maintaining the clusters. Hence we have considered a non-cluster based network with random movement of nodes for our analysis. Our principal aim is to reduce the amount of flooding of the route-request (RREQ) packets in the network so that the overhead can be reduced. In order to achieve this we propose a prefetching algorithm which involves two steps. First, we timestamp each and every route cached in a node´s route-cache table based on the mobility of the nodes. Second, we initiate prefetching of only the frequently used entries from route-cache table when their respective timestamps are on the verge of expiring. Simulations carried out on DSR have shown that this technique can reduce redundant flooding to a great extent, thus making DSR more efficient.