Edinburgh Napier University

  The IPv6 Routing Protocol for Low-power and Lossy Networks (RPL) has been recently standardized for routing in the constrained Internet of Things networks. Unfortunately, the RPL storing mode has been found restricted by storage limitations in the routers along the downward path. In fact, unreachable destinations problem may be easily encountered when a router fails, due to lack of memory, to store a routing entry for a target in its associated sub-network. In addition, the under-specification of Downward Advertisement Objects (DAOs) represents another serious issue in RPL. The timing of when and how often DAOs should be emitted is not fully addressed which may lead to inefficient implementations. Motivated by these observations, this paper presents an enhanced version of RPL called Enhanced-RPL. In the proposed enhancement, to mitigate the problem of storage limitation of the node's preferred parent, a node is allowed to distribute prefixes belonging to its sub-network among multiple parents. In addition, a more cautious approach for emitting DAOs is proposed to mitigate the issue of DAOs under-specification mechanisms. Our simulation experiments demonstrate that the proposed Enhanced-RPL outperforms the RPL standard by an average of up to 64% in terms of control-plane overhead and 30% regarding the packet delivery ratio.