Formal Analysis of a Distributed Fault Tolerant Clock Synchronization Algorithm for Automotive Communication Systems

A synchronized time base is indispensable for a time- triggered system since all activities in such a system are triggered by the passage of time. Distributed fault-tolerant clock synchronization algorithms are normally used to achieve the synchronized time base. As a state-of-the-art representative of the time-triggered systems for automotive applications, FlexRay uses a fault-tolerant mid-point algorithm to achieve the synchronized time base. Correctness of the algorithm plays a crucial role as most of the protocol services rely on the fact that there exists a synchronized time base in the system. Due to the distinguished characteristics of the algorithm, we propose a case-analysis based technique for the formal analysis of the algorithm. We show that the case analysis technique can greatly facilitate our formal analysis of the algorithm. Mechanical support with Isabelle/HOL, a theorem prover, is also discussed.