Performance Analysis of FDDI Token Ring Networks: Effect of Parameters   and Guidelines for Setting TTRT
  The performance of Fiber-Distributed Data Interface (FDDI) depends upon several workload parameters; for example; the arrival pattern, frame size, and configuration parameters, such as the number of stations on the ring, extent of the ring, and number of stations that are waiting to transmit. In addition, the performance is affected by a parameter called the Target Token Rotation Time (TTRT), which can be controlled by the network manager. We considered the effect of TTRT on various performance metrics for different ring configurations and concluded that a TTRT value of 8 ms provides a good performance over a wide range of configurations and workloads. 
R. Jain