A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s> IV. RPL LIMITATIONS AND DRAWBACKS <s> 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. <s> BIB001 </s> A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s> IV. RPL LIMITATIONS AND DRAWBACKS <s> Routing Protocol for Low Power and Lossy networks (RPL) is the de-facto standard for routing in resource-constrained low-power and lossy networks (LLNs) which represent the building block for the ever-growing Internet of Things (IoT). RPL along with other routing protocols make the deployment of Trickle algorithm as a mechanism for controlling and maintaining the routing traffic frequency. Trickle employs two different techniques to manage the routing traffic efficiently. Firstly, the suppression phase where a node suppresses its control data transmission if it is redundant. Secondly, the traffic frequency adaptation, where the nodes increase their sending rate when discovering inconsistency while slow down their rate as the network becomes stable. The efficiency of Trickle has been approved in terms of power consumption and scalability, however, imposing the so-called listen-only period as a solution for the short-listen problem comes at the expense of increased convergence time. Thus, in this paper, an enhanced version of Trickle is proposed, namely, E-Trickle which solves the short-listen problem without imposing the listen-only period. Simulation results show that E-Trickle have decreased the convergence time by up to 43% while preserving the same efficiency of Trickle in terms of power consumption, scalability and reliability. <s> BIB002
As the de-facto standard for routing in IoT networks, a plethora of recent studies have evaluated RPL performance reporting several limitations and pitfalls that need to be addressed BIB001 - BIB002 . In the next subsections, we elaborate on the key weaknesses and limitations reported in the literature related to RPL's OFs (Section V-A), RPL' downward routing (Section V-B) and RPL's routing maintenance (Section V-C). A summary of these limitations is presented in Table 2 .