BMRF: Bidirectional Multicast RPL Forwarding

Nowadays, the transition of Wireless Sensor Networks (WSNs) to Internet Protocol version 6 (IPv6), in particular to IPv6 over Low power Wireless Personal Area Networks (6LoWPAN), is evident [1]. However, in most commonly used implementations, not all IPv6 features are available. For example, current implementations are not very optimized for multicast, despite the many benefits multicast can offer with respect to the number of radio transmissions and the amount of consumed energy.In this paper we present Bidirectional Multicast RPL Forwarding (BMRF), a new multicast protocol that combines the best features of the Routing Protocol for Low Power and Lossy Networks (RPL) multicast on the one hand and of Stateless Multicast RPL Forwarding (SMRF) on the other hand. The main features are bidirectionality and the ability to offer a choice between Link Layer broadcast and Link Layer unicast for which the threshold to decide for a mote, which link layer mode to choose, is mainly based on its number of interested children and the duty cycling rate. An implementation of BMRF is realized in Contiki. Our measurements show that BMRF, when using the optimal configuration, results in less radio transmissions, and less energy consumption, and higher packet delivery ratio compared to SMRF, often at the cost of a higher end-to-end delay.