The relevance and impact of IPv6 multicasting for Wireless Sensor and Actuator Networks based on 6LoWPAN and Constrained RESTful Environments

Wireless Sensor and Actuator Networks (WSANs) will play an essential role in the future Internet of Things. Wireless communication is an important enabler that provides ease of deployment and reduced installation costs but puts strong constraints on the used communication protocols regarding available bandwidth and reliability. WSANs based on 6LoWPAN allow to use IPv6 within most constrained wireless networks with global end-to-end connectivity between smart objects. The multicasting capabilities of IPv6 are mostly neglected in state of the art implementations of 6LoWPAN due to the limited scenarios within wireless sensor networks (WSNs). This paper presents a concept of a Web service based communication stack that uses transient link-local IPv6 multicast addresses for process data exchange between sensors and actuators by binding a shared network variable to the IPv6 multicast address. It will be shown how this concept allows devices to efficiently interact in a peer-to-peer interaction style without the need of a central controller. Furthermore, it will be sketched how the engineering process of control logic can be simplified through this approach. Finally, a reference implementation based on Contiki is presented accompanied with simulation results that compare traditional client/server based communication with the novel interaction mechanism analyzing the scalability effects on a WSAN.