Deferring real-time traffic for improved non-real-time communication in FDDI networks

The fiber distributed data interface (FDDI) is suitable for real-time communication because of the high speed and the performance guarantees it provides. However, these guarantees are achieved at the expense of non-real-time traffic because the real-time messages are given higher priority over non-real-time messages,resulting in excessive delays for non-real-time messages. In this paper, we propose a scheme for reducing the response time of non-real-time messages while still providing the same guarantees to real-time messages. In particular, the proposed approach gives higher priority to real-time messages only when it is absolutely necessary in order for them to meet their deadlines. Non-real-time messages are thus transmitted ahead of real-time messages whenever possible. We present an algorithm for determining when and by how much the transmission of a real-time message can be deferred without jeopardizing its deadline. The proposed approach is evaluated through simulation. The simulation results show that a substantial reduction in the mean response time of non-real-time messages is achieved when using the proposed approach.