A schedulability analysis of tasks and network traffic in distributed real-time systems

In real-time systems the deadlines of each task must be met. A pre-run-time schedulability analysis becomes necessary to prove that the existing software and target hardware will meet the real-time application constraints. In a real-time distributed system, the messages transmitted through the network are also time constrained. However, some new problems arise when one applies existing task scheduling algorithms to schedule the network traffic. The main goal of this paper is to define the boundaries between these two domains of scheduling. After an introduction to fieldbuses and real-time systems, we present an equivalence between tasks and messages as well as between processors and networks, which are much different in practice but have strong similarities from the scheduling point of view. Finally, we analyse the new constraints introduced by the presence of smart transducers/transmitters in fieldbus applications and we define the scheduling algorithms adapted for this type of applications.

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