3. Message scheduling

3.1 Introduction

As we have already pointed out, real-time and distributed applications impose time constraints on task execution; these constraints have a direct impact on the messages exchanged between tasks when they are placed on different processors.

In a real-time application, some tasks may have strict time constraints, while others may not. Similarly, messages exchanged between these tasks may or may not have strict constraints. For example, an alarm message must be transmitted and received with strict constraints, otherwise it will not be possible to deal with the cause of the alarm before it causes a failure, whereas a file transfer does not generally require strict time constraints. If a message arrives after the deadline, it is considered lost. A...