In a distributed hard real-time system, communications between tasks on different processors must occur in bounded time. The inevitable communication delay is composed of both the delay in transmitting a message on the communications media, and also the delay in delivering the data to the destination task. This paper derives schedulability analysis bounding the media access delay and the delivery delay. Two access protocols are considered: a simple timed token passing approach, and a real-time priority broadcast bus. A simple delivery approach is considered where the arrival of a message generates an interrupt—the so-called ‘on demand’ approach.