Fault-Tolerant Clock Synchronization in CAN

Luís Rodrigues and Mário Guimarães and José Rufino

Selected sections of this report will be published in the Proceedings of the Proceedings of the 19th IEEE Real-Time Systems Symposium, Madrid, Spain, December 2-4, pp.420-429, 1998.


This paper presents a new fault-tolerant clock synchronization algorithm designed for the Controller Area Network (CAN). The algorithm provides all correct processes of the system with a global timebase, despite the occurrence of faults in the network or in a minority of processes. Such global time-frame is a requirement of many distributed real-time control systems.

Designing protocols for CAN is justified by the increasing use of this network in industrial automation applications. CAN owns a number of unique properties that can be used to improve the precision and performance of a clock synchronization algorithm. Unfortunately, some of its features also make the implementation of a fault-tolerant clock synchronization service a non-trivial task. Our algorithm addresses both the positive and the negative aspects of CAN.

Also available extended report (gzip postscript), (pdf) .

Luís Rodrigues