Consistency of Path based Upward Path Recovery Method to Reduce Path Recovery Delay for RPL

In IoT (Internet of Things) networks, RPL (IPv6 Routing protocol for Low Power and Lossy Networks) is preferred for reducing routing overhead. In RPL, a node selects one parent node which includes the lowest routing metric among its neighbors and the other neighbors are stored as immediate successors. If the selected parent node is lost, the node selects a new parent node among the immediate successors. However, if the new path also includes the same intermediate node which is lost in previous path, it also fails to transmit upward packets. This procedure might be repeated until the new path is selected which does not include the lost immediate node. In this paper, we therefore propose a new path recovery method to reduce the unnecessary repetition for upward path recovery. When a node receives routing message, it calculates the hash value and sets 1 to a new field in the routing message. Based on the field, the node estimates an approximate number of ancestors that are shared between each paths. When loss of upward path is detected, the node selects a new path according to both approximate number and the routing metric. Therefore, a new path which dose not include same ancestors with the previous path is selected and data packet can be resumed immediately.