PROPOSAL AND EVALUATION OF TIME-CRITICAL COMMUNICATION PROTOCOL ON LAN

In the field of control and communication using LAN, such as plant control, there exists a requirement for the time critical property that the data transfer should be completed in the specified time (time window), in addition to the requirement for the high speed. In the timed token protocol (TTP) that has been used in FDDI and other systems, however, the transfer time increases when the input traffic exceeds the system specification, making it impossible to maintain the time-critical property. This paper proposes an extension of TTP where only the data that can be transferred within the time window are allowed to transverse by applying dynamic distributed management to the data transmission queue in each node. To demonstrate the performance of the proposed protocol, simulations are executed under various conditions; and it is verified that the protocol is effective when applied to the time-critical communication.