Performance analysis of the FDDI MAC protocol

The fiber distributed data interface (FDDI) media access control (MAC) mechanism supports two classes of traffic: synchronous and asynchronous. The asynchronous traffic can further be divided into eight subclasses according to priority. The FDDI performance is closely related to its operational parameters, such as the number of stations on the ring, the frame size, and the target token rotation time (TTRT). The authors analyse the delay and throughput of the FDDI MAC protocol while both the synchronous and eight asynchronous traffic types are present. A simulation model based on the M/D/1 queuing system is developed. Two configurations of 45 and 100 stations, respectively, have been studied. From the simulation results, several operational guidelines for setting TTRT are proposed. A delay prediction procedure is developed by incorporating Lagrange´s form of the interpolating polynomial. It can predict the main frame delay within 2.5% of the simulation value. The prediction procedure in conjunction with operational guidelines provides an effective tool for tuning the FDDI network