Scheduling time constrained messages on miniMAP

The existing OSI standards, in their present form, cannot satisfy the requirements imposed by time-critical applications. The solution being sought is for a middle tier network (MiniMAP), between the full seven layer network (MAP) and the Fieldbus type networks, which will guarantee completion of critical actions within the specified time window. The paper presents a performance analysis, based on simulation results, of the three layer MiniMAP (with MMS, LLC type 3 and 4 MAC access classes) with an end-to-end communications scheduler on the top of it. The authors study the performance of the protocol under four different scheduling policies (First Come First Served, Minimum Deadline First, Priority, Value) and using a symmetric load pattern. The performance metric for the time-constrained traffic is the percentage of messages received within their deadlines. It is shown that when employing an end-to-end scheduler the performance of MiniMAP improves significantly (up to 48%).