A few years ago, the IPv6 Routing Protocol for Low-power and Lossy Networks (RPL) was proposed by IETF as the routing standard designed for classes of networks in which both nodes and their interconnects are constrained. Since then, great attention has been paid by the scientific and industrial communities for the protocol evaluation and improvement. Indeed, depending on applications scenarios, constraints related to the target environments or other requirements, many adaptations and improvements can be made. So, since the initial release of the standard, several implementations were proposed, some targeting specific optimization goals whereas others would optimize several criteria while building the routing topology. They include, but are not limited to, extending the network lifetime, maximizing throughput at the sink node, avoiding the less secured nodes, considering nodes or sink mobility. Sometimes, to consider the Quality of Service (QoS), it is necessary to consider several of those criteria at the same time. This paper reviews recent works on RPL and highlights major contributions to its improvement, especially those related to topology optimization, security and mobility. We aim to provide an insight into relevant efforts around the protocol, draw some lessons and give useful guidelines for future developments.

Minimizing the energy consumption and hence extends the network lifetime is a key requirement when designing an efficient sensor network protocol. QoS-aware routing in Wireless Sensor Network (WSN), aims to take into account other networks performance aspects as minimizing end-to-end delay (as well as jitter), reducing packet loss rate while minimizing the energy consumption of the network during data transmission. These objectives are sometimes conflicting, and therefore tradeoffs must be made between energy conservation and QoS considerations. The general problem can be reformulated as a Multi-Constrained Optimal Path problem (MCOP), and is known as NP-complete. The latter raises a real challenge, as sensor nodes are very limited in resources capabilities, we propose to use fuzzy inference mechanism to seek a good tradeoff between all given metrics and constraints. This paper discusses the implementation of combining several routing metric, using fuzzy logic to design a RPL objective function, the routing standard for the Internet of Things. The proposal is integrated on Contiki operating system and his deployment were performed on a real world indoor WSN. Obtained results show improvements compared to the common implementation of the RPL protocol, and demonstrate relevance of our contribution.

In recent years, Internet of Things has changed the way people work and live, thereby opening new opportunities. This article describes a framework architecture for interconnecting several wireless sensor networks to the Internet to achieve the vision of Internet of Things. Connecting things together is done through gateways that act as single points of failure to bridge the connection between wireless sensor network and the traditional wired Internet. To cope with the unreliable nature of wireless links and scale to a large number of sensors and wireless sensor networks, several gateways should be installed. Given a number of previously deployed gateways, the contribution of this article is twofold. First, it focuses on choosing the most suitable ones for connecting wireless sensor networks to the Internet in a efficient and cost-effective manner, using integer linear programming to develop the mathematical model. Second, a network topology that puts the integration of wireless sensor networks to the Internet in place is built. A three-layer architecture is used in such a way that the intermediate layer adapts dynamically to network changes and evolution. Gateway selection procedure at this layer was implemented using CPLEX linear solver, and the gateway was integrated on Raspberry Pi cheaper hardware which serves as the routing protocol for low-power and lossy network root for the wireless sensor network configuration. Experiments and real deployments have been conducted to demonstrate the effectiveness of the proposed scheme.