ferring Real-Time Traffic for Improved ime Communication in FDDI Networks

The fiber distributed data interface VDDQ is suit- able for real-time communication because of the high speed and the performance guarantees it provides. However, these guaran- tees are achieved at the expense of non-real-time traffic because the real-time messages are given higher priority over non-red- 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 pro- posed 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 dead- line. 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.