The paper introduces a mechanism to implement distributed scheduling for the CAN-bus resource in order to meet the requirements of a dynamic distributed real-time system. The key issues considered here are multicasting, distinguishing between hard real-time, soft real-time, and non-real-time constraints, achieving high resource utilization for the CAN-bus, and supporting dynamic hard real-time computing by allowing dynamic reservation of communication resources. A real-time communication system

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... (RTCS) constitutes the backbone of distributed control applications. In order to support the timely completion of distributed real-time activities, RTCS must ensure bounded delivery delay for real-time messages. Assuming the existence of hard real-time, soft real-time and non-real-time-distributed activities in a complex distributed real-time system, communication activities can also be considered to have hard real-time, soft real-time, and non-real-time natures. While the timeliness of hard real-time communication must be guaranteed, the delivery delay of a soft real-time message may exceed the desired bound in overload situations. For the delivery of non-real-time messages no delay bound is de"ned. This behavior of the real-time communication must be provided to the application level by the RTCS. The design of a real-time communication system must exploit the predictability features of the lower system levels, in order to achieve predictable behavior at the higher levels. If a communication medium exhibits unpredictable behavior (e.g. unbounded transmission delay) (M. Ali Livani) 0967-0661/99/$ -see front matter 1999 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 7 -0 6 6 1 ( 9 9 ) 0 0 1 2 8 -8