RPL routing protocol in advanced metering infrastructures: An analysis of the unreliability problems

To allow pervasive and distributed monitoring and control of grid devices and resources, the next-generation electricity grid needs a scalable and reliable two-way communication infrastructure, known as Advanced Metering Infrastructure (AMI). In such communication system, characterized by the interconnection of thousands of resource-constrained embedded devices, such as smart meters and intelligent electric devices (IEDs), the routing protocol plays an essential role to guarantee a timely and reliable communication service. In this paper we investigate the performance of RPL, the IPv6 routing protocol recently standardized by IETF to meet the requirements of such networks. Special emphasis is given to the analysis of route-level attributes, such as path stretch, route lifetimes, dominance, and flapping, which are used to estimate the quality and stability of the RPL routes. Our results show that RPL nodes may suffer from severe unreliability problems, mainly because RPL often selects sub-optimal paths with low quality links. Furthermore, RPL routes are strongly dominated by a single route, and this may prevent RPL from quickly adapt to link quality variations. We believe that the findings of this study may facilitate the design of new mechanisms to improve the reliability and adaptability of RPL.