Distributed embedded systems (DESs) that perform critical tasks in unpredictable environments must be reliable, hard real-time, and adaptive. Since a DES comprises nodes that rely on a network, the network must provide adequate support: it must be reliable, convey messages on time, and meet new real-time requirements as the nodes adapt. Ethernet is ill-suited for such hard real-time adaptive systems, but it can be made suitable.
The Flexible Time-Triggered (FTT) paradigm already supports hard real-time message exchanges and the necessary flexibility to meet evolving hard real-time requirements, but its Ethernet implementations had reliability limitations. To address these, we designed FTTRS, a communication subsystem that tolerates permanent and transient faults, even if they occur simultaneously, while keeping the paradigm’s key features: support for both the timely exchange of periodic and sporadic real-time messages, and support for updating the real-time parameters of these messages at runtime. In this paper we present FTTRS, the first Ethernet-based communication subsystem specifically designed for highly reliable hard real-time adaptive DESs.