A study of the neighbor unreachability detection mechanism to improve performance of RPL protocol

Abstract

Recently, there is a rapid increase in the deployment of Internet of Thing (IoT) networks in many areas such as smart building, industrial plants and agriculture fields. However, this type of network need to be carefully operated because there are many constraints that can impede the performance of the network such as the unreliable wireless channel conditions, and the limited processing capability of sensor motes. Internet Engineering Task Force (IETF) proposed IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL), which is designed for IoT devices but some mechanisms defined in the RPL standard document (RFC 6550) are underspecified. This issue can lead to interoperability problem between multiple hardware platforms. In this paper, we focus on one of the underspecified mechanisms in RPL, Neighbor Unreachable Detection (NUD) mechanism. Two approaches for improving NUD mechanism are proposed and implement in Zolertia Z1 motes: NUD with hello packets and NUD with DIO messages. The results from the experiments that vary the interference levels and consider node moving scenario show that both of the proposed NUD mechanisms can provide much better performance in term of Packet Reception Ratio (PRR) than the original NUD implementation in ContikiOS. The NUD implementation with DIO messages cannot match the similar level of performance of the NUD implementation with hello packets but it can be implemented without adding more complexity to the RPL protocol.