Securing cell scheduling function in TSCH-based industrial IoT networks

6TiSCH is a widely adopted low-power networking standard for Industrial IoT applications that provides highly reliable communication with low latency. Cell scheduling is one of the crucial components in 6TiSCH networks, as it determines packet transmission schedules based on time and channel allocation policy. The IETF published the Minimal Scheduling Function (MSF) and associated 6top (6P) protocol to manage cell schedules dynamically. However, security of the 6TiSCH architecture, particularly the vulnerabilities within the MSF and its associated 6P, has not been fully explored in the literature. This paper identifies vulnerabilities present in the MSF and 6P protocol, and demonstrates the feasibility of two different types of attack called cell depletion attack and schedule instability attack. In both attacks, the main objective of adversary is to consume scheduling resources and make the schedule unstable by performing unnecessary and incorrect 6P transactions. These attacks disrupt the communication schedule of victim nodes as well as victims’ successors, thus causing schedule instability, reduced reliability and increased energy consumption. The Minimal Security Framework standardized by IETF cannot handle such attacks on the MSF. Therefore, this paper proposes a comprehensive strategy (SCSF-WELA) that combines rule-based approach and Weak Estimation Learning Automata (WELA) to detect and prevent malicious behaviour by an attacker. The proposed solution integrates into the standard MSF without additional communication overhead. Through extensive simulations using the 6TiSCH simulator, we verify that the impact of these attacks is significant as they can increase schedule instability by four times and the 6P messaging overhead by 42% in a 60-node network. Furthermore, the proposed SCSF-WELA contermeasure shows substantial improvements in network stability, energy efficiency, and overall performance under those attacks.