Performance evaluation of real-time message delivery in FDDI networks

This paper presents the simulation results on the FDDI medium access protocols and two modified FDDI medium access protocols. For synchronous traffic, there is usually a deadline requirement which specifies the time allowed for the packet to reach its destination. For FDDI, if the delay bound is D, the stations have to set the TTRT=D/2 in order ensure the deadline requirement can be met. This gives the total synchronous bandwidth as D/2-T/sub ring/. However, the total usable synchronous bandwidth is D-T/sub ring/ which means the capability of supporting synchronous bandwidth is halved. Zheng (1992) and Leung (1994) have proposed new schemes to overcome these problems and have no diverse effect on asynchronous throughput. Extensive simulations have been carried out on these schemes to evaluate their performance characteristics. Also, a frame-drop policy at source station is proposed and shown to be effective in improving performance on synchronous transmission.