The performance behavior of an FDDI (fiber distributed data interface) system with synchronous traffic as well as an extended FDDI (FDDI-II) system with isochronous and asynchronous traffic is evaluated. Multiple asynchronous priorities are considered, one priority level at each station. an iterative algorithm to calculate the first two moments of the cycle (i.e. token rotation) time is presented, and the major system characteristics are derived from the analysis in terms of queue-length distributions and mean waiting times of the packets. Since the model considers queues with limited buffer size, loss probabilities of data packets can also be calculated. Some results obtained by the approximate analysis are discussed using example configuration, and the accuracy is validated by detailed computer simulations. The complexity and convergence behavior of the algorithm is studied, and it is shown that the algorithm converges very quickly.>