A bandwidth allocation scheme for time constrained message transmission on a slotted ring LAN

We study the problem of transmitting time constrained synchronous messages in a slotted ring based local area network, carrying synchronous and asynchronous traffic. A bandwidth allocation scheme for synchronous messages is developed on top of a media access control protocol that assigns preemptive priority to synchronous traffic over asynchronous traffic. We derive sufficient conditions for schedulability of time critical synchronous messages and show that the scheme achieves high levels of schedulable utilization. A slot access protocol is proposed for synchronous streams that implements the allocation scheme with minimal additional overhead and loss of schedulable utilization. The protocol is distributed in the sense that any node can locally determine if it can use a slot, without exchanging any explicit messages with other nodes