Vulnerability in Cell Scheduling Function for 6TiSCH Networks: Impact and its Mitigation

The 6TiSCH standard is widely adopted for Industrial IoT applications, offering low latency and high reliability. Cell scheduling plays a critical role in 6TiSCH networks by determining packet transmission schedules in terms of timing and channel allocation. The IETF introduced the Minimal Scheduling Function (MSF) and the 6top protocol to facilitate schedule management dynamically. This paper investigates the vulnerabilities associated with cell scheduling and the 6top protocol in 6TiSCH networks. We have demonstrated the existence of a cell depletion attack which can be launched by a compromised node, and its potential to disrupt the proper functioning of cell scheduling. This attack adversely affects transmission reliability, end-to-end latency, and energy consumption of victim nodes and their child nodes. To address the impact of this attack, we have proposed a defence mechanism which can be easily incorporated into the MSF scheduling function. Our approach incorporates parent-child authentication and validation measures to ensure that only legitimate nodes participate in the scheduling process. Through extensive simulations, we have verified that the proposed cell depletion attack significantly degrades network performance and increases the energy consumption of victim nodes by 41% in a 60-node network compared to normal functioning of scheduling function, leading to a significant decrease in device lifespan. However, when our defence mechanism is implemented, we observe a significant improvement in network performance even in the presence of the attacker.