BuST: Budget Sharing Token protocol for hard real-time communication

Timed-token networks, such as FDDI, support both synchronous real-time traffic and non real-time traffic (asynchronous messages). The medium access scheme of FDDI guarantees up to one half of the total network bandwidth for synchronous communication. Further enhancements, such as FDDI-M, improve the bandwidth dedicated to real-time messages. However, the ability of timed-token protocols to guarantee synchronous message deadlines highly depends on specific Synchronous Budget Allocation (SBA) schemes. This paper introduces BuST, the Budget Sharing Token protocol which improves the management of periodic real-time traffic, while guaranteeing a minimum throughput for non real-time messages, with respect to existing techniques. We evaluate the performance of BuST, in comparison with FDDI and FDDI-M, considering a Synchronous Budget Allocation (SBA) scheme proposed in the literature, using the Worst-Case Achievable Utilization (WCAU) as performance metrics. We demonstrate that the performance achieved by BuST is better or, in a few cases, equal to FDDI and FDDI-M.