A protocol for real-time message scheduling in LAN/MAN

The authors propose a protocol, named token passing with concession (TP/C), for real-time messages and communication channel scheduling, and compare it with CSMA/CD, virtual time CSMA, and window and token bus protocols considering message loss under various workload and network parameters. The TP/C protocol can be implemented on top of the existing contention-free protocols such as the token bus, token ring, or FDDI ring protocol. The analysis results indicate that TP/C has a performance comparable to those of the other real-time protocols, but that it has more predictable behavior. The performance metrics such as percentage of messages lost and effective channel utilization were obtained using simulation under various network and protocol parameters. The authors also discuss how the protocol can be implemented for hard-real-time applications