End-to-End Delays of Event-Triggered Overlay Networks in a Time-Triggered Architecture

Event-triggered overlay networks are a solution for extending time-triggered networks with support for additional event-triggered communication activities. In addition to time-triggered message transmissions, applications can request the dissemination of messages at points in time that need not be statically predefined at design time. Thus, the flexibility is improved and the reuse of event-triggered legacy applications becomes possible. This paper analytically describes the delays of message transmissions on such an event-triggered overlay network on top of a time-triggered physical network. Knowledge about these message delays is significant for the development of new real-time applications, as well as for migrating existing applications from a physical event-triggered network to an event-triggered overlay network. After identifying the determinant parameters, we explain the computation of the worst-case and best-case message delays. The generic analytical description is applied to real-world examples and compared to the message delays that have been observed in actual implementations of event-triggered overlay networks on top of TTP and Time-Triggered Ethernet.