Token-ring adapter-chipset architectural considerations for real-time systems

The results of implementation studies utilizing commercially available IEEE 802.5 chip sets and boards are reported. Serious implementation flaws were discovered that prevent the full potential of the IEEE 802.5 token ring standard from being realized for real-time applications. Specifically, unbounded delays can be introduced which not only destroy the desired response time determinism offered by algorithmic scheduling, but which also negate asynchronous alert class guarantees and unnecessarily increase other asynchronous response times. An analysis is made of the scheduling properties of current implementations, and modifications to the current implementations are proposed to allow them to realize the full potential offered by the IEEE 802.5 standard for real-time applications