Evaluating and improving the scalability of RPL security in the Internet of Things

Wireless Sensor and Actuator Networks (WSANs) will represent a key building block for the future Internet of Things, as a cheap and easily-deployable technology to connect smart devices on a large scale. In WSAN the Routing Protocol for Low-Power and Lossy Networks (RPL) has a crucial role as the standard IPv6-based routing protocol. RPL specifications define a basic set of security features, without which it would be open to disruptive routing attacks. However, the impact of these features on the WSAN performance has not been thoroughly investigated yet. The contribution of this paper is two-fold. First, we extensively evaluate the impact of security mechanisms on the scalability of WSANs by means of both simulations and real experiments. We show that the protection against eavesdropping and forgery has a modest impact on the performance, whereas the protection against replay has a more considerable impact, especially on the network formation time which increases noticeably. Despite this, we show that protecting against replay reduces the number of control messages exchanged and improves routes optimality. For these reasons, we recommend to always use the security mechanisms. Finally, we propose a standard-compliant optimization for defending against replay that reduces the impact on the overall performance.