Availability evaluation of IoT systems with Byzantine fault-tolerance for mission-critical applications

Byzantine fault-tolerant (BFT) systems are able to maintain the availability and integrity of IoT systems, in the presence of failure of individual components, random data corruption or malicious attacks. Fault-tolerant systems in general are essential in assuring continuity of service for mission-critical applications. However, their implementation may be challenging and expensive. In this study, IoT Systems with BFT are considered. Analytical models and solutions are presented as well as a detailed analysis for the evaluation of the availability. BFT is particularly important for blockchain mechanisms, and in turn for IoT, since it can provide a secure, reliable and decentralized infrastructure for IoT devices to communicate and transact with each other. A continuous-time Markov chain is used to model the IoT systems with BFT where the breakdown and repair times follow exponential distributions, and the number of the Byzantine nodes in the network follows various distributions. The presented numerical findings demonstrate the relationship between the number of nodes in the system, the proportion of honest users, and the overall availability. Based on the model, it can be inferred that the correlation between the scale of the system (nodes) and network availability is non-linear. Additionally, results show that even for relatively small-size systems with 40 nodes, an average availability greater than 0.999 and an estimated downtime per year that is less than 9 h is possible.