How hard is hard real-time communication on field-buses?

Continuity of service and bounded and known message delivery latency, are reliability requirements of a number of real-time applications, such as those served by field-buses. The analysis and design of such networks, w.r.t. timing properties, has been based on no-fault scenarios, rather than under a performability perspective. In this paper, we do an analytical study of the inaccessibility of CAN and PROFIBUS. The study reveals that previous studies on the access delays of these field-buses were too optimistic, from a performability viewpoint.