On the design of communication protocols for safety-critical automotive applications

Desirable characteristics of a protocol for a computer network handling safety-critical functions in a car are discussed. The protocol should facilitate the handling of errors occurring in the network. It is suggested that only a time-driven cyclic protocol with pre-scheduled message exchanges can provide the desired functionality. With such a protocol, the meeting of deadlines can be guaranteed. Furthermore, many faults are detectable as they cause the network traffic to differ from the expected. The membership agreement task is also simplified by a time-driven protocol. Two time-driven protocols, TTP and EDP are briefly reviewed. It is found that TTP is more flexible and provides a lower degree of overhead. However, the simplicity of EDP accounts for a reduction of the number of possible fault modes and a simplification of the fault handling