A Probabilistic Analysis of End-To-End Delays on an AFDX Avionic Network

AFDX (Avionics Full DupleX Switched Ethernet, ARINC 664) developed for the Airbus A380 represents a major upgrade in both bandwidth and capability. Its reliance on Ethernet technology helps to lower some implementation costs, but guaranteed service presents challenges for system designers. An analysis of end-to-end transfer delays through the network is required in order to determine upper bounds. In this paper, we propose to compute probabilistic upper bounds for end-to-end delays on avionic flows. Such upper bounds can be exceeded with a given probability p, and are relevant in the context of avionics, where functions are designed to give accurate results even if they miss some frames. The stochastic network calculus approach analytically determines a probabilistic upper bound, whereas the simulation approach gives an experimental upper bound. The former may be used for new certification needs since it assures that the probability of exceeding the computed upper bound is not greater than p. The latter closely approximates actual network behavior and can help to give some idea of the pessimism of the stochastic network calculus upper bound. The two approaches have been developed in the context of an industrial AFDX network configuration.