Fault Injection Framework for Assessing Fault Containment of TTEthernet Against Babbling Idiot Failures

Abstract

In safety critical communication systems, faulty nodes can monopolize a channel by transmitting untimely messages at random intervals and thus resulting in the failure of the system. This failure is known as a babbling idiot failure. This could be costly and catastrophic for safety critical systems, therefore these failures are avoided in time triggered communication systems by implementing fault tolerant functions such as local or central guardians. Research works evaluating the guardian functionality for real time networks such as Flexray and TTP have been carried out. This work evaluates the guardian functionality of the TTEthernet protocol. TTEthernet enforces a TDMA scheme for time triggered traffic and traffic policing for rate constrained traffic thereby protecting the network against babbling idiot failures. However these guardian functionality was not extensively evaluated. Dependability evaluation by fault injection on the entire TTEthernet communication system as a whole has not been extensively studied. In this paper we exploit a novel fault injection framework to generate babbling idiot failures for the purpose of verifying TTEthernet implementations with respect to fault containment. The framework adopts a novel cut-through approach abstracting the fault injector from both the end systems and switches, thereby facilitating portability and ease of use. This work introduces a fault injection framework to effectively verify babbling idiot fault tolerance of TTEthernet hardware implementations. In addition, it provides a means to evaluate the effect of various network faults on applications running on top the protocol. Test results carried out indicate the effect of babbling idiot messages on the latency and jitter of traffic over the TTEthernet network.