Analytical Assessment of the Precision Degradation Caused by Faults in a Fault-Tolerant Master/Slave Clock Synchronization Service for CAN

The main goal of a clock synchronization service is to keep a consistent perception of time among the nodes of the system. In this context, consistency means that at any instant, the values of all the clocks in the system do not differ more than a given amount, which is called the precision. Moreover, clock synchronization is said to be fault tolerant if the intended precision is guaranteed despite the occurrence of the faults included in the fault model. In this paper, we consider a specific fault-tolerant master/slave clock synchronization service for the Controller Area Network (CAN) field bus, and analyze its precision under different fault assumptions. The equations obtained in our analysis show that, when using master redundancy, inconsistent channel faults may have a negative impact on the guaranteed precision.