FDDI Models

Abstract

Although many FDDI analytical studies have already been published, they contain simplifying assumptions. The main difficulty for the analysis of the FDDI MAC protocol is the high degree of complexity and interdependence of the various processes that describe the operations of the protocol itself. In fact, when a station has seized the token, synchronous frames (if any) are always transmitted, whereas asynchronous frames are only transmitted if the token is early. This implies that there are interdependencies between the cycle length, the service period at one station, and the service periods at subsequent stations. Therefore, exact analytically-tractable solutions for an FDDI network are very difficult to formulate. Simplifying assumptions thus have to be made in order to obtain analytically-tractable solutions. Furthermore, even when synchronous traffic alone is transmitted, only approximate solutions are known for the resulting model, i.e., a polling system with an exhaustive time-limited (visit) service discipline (see Section 2.1).