Pre-emptive Dynamic Source Routing: A Repaired Backup Approach and Stability Based DSR with Multiple Routes

DSR algorithm is applied to selects best path for communication between two nodes in a highly dynamic environment. As highly dynamic environment changes frequently, the probability of breakage of established path is high in such environment. Every time when established path breaks, a new route has to be discovered for communication between the nodes. In order to avoid path discovery every time, we propose themodification of the existing DSR algorithm. The modification proposed is based on a backup route (second best route). The back up routes will be provided by the destination node to the source node along with the best route during the process of path discovery. During the path maintenance process, in case any intermediate node identifies that the signal strength falls below a threshold indicating that the established route is about to break, the intermediate node sends a caution message to the source node. The source node switches the communication through the backup path, apprehending that the established route is about to break. As the communication through the backup route takes place, the previous established route is repaired, if possible. If repaired, the route will act as the new backup route. This process of toggling between backup route and established route reduces the call for path discovery to a large extent. The stability in consideration of failure of common link and nodes in the back up repaired algorithm has been investigated with new algorithm for stable route selection.