Hard and soft real time message scheduling on Ethernet networks

The nature of Ethernet Multiple Access Control (CSMA/CD) makes it impossible to get a deterministic medium access time to guarantee real time constraints. We propose a new Ethernet Access protocol called EDF-CSMA which is inspired from the optimal scheduling centralized algorithm EDF (Earliest Deadline First). This protocol compatible with CSMA, gives guaranteed prediction to real-time messages and performs better guarantee results than protocols in previous works such as: CSMA-DCR, DOD-CSMA/CD, VTCSMA and RTCC. We also extend this protocol to realistic context, where it treats at the same time hard real time messages with deadline guarantees, soft real time messages with minimizing their deadline missing and non real time messages to be sent in finite time.