Effectiveness of the FDDI-M protocol in supporting synchronous traffic

Timed token networks such as fiber distributed data interface (FDDI) networ ks have been widely deployed to support synchronous traffic. However the me dium access control (MAC) protocol of FDDI allows transmission of synchrono us messages up to at most one-half of the total bandwidth of the network. S hin and Zheng have proposed a modification to the FDDI MAC protocol, called FDDI-M, which can double a ring's ability in supporting synchronous traffi c (K.G. Shin, G. Zheng, IEEE Transactions on Parallel and Distributed Syste ms 6 (1995) 1125-1131). It is widely known that the ability of timed token protocols such as FDDI to guarantee synchronous message deadlines is very d ependent on the synchronous bandwidth allocation (SBA) schemes used, but th e original paper does not address this issue. In this paper, we will compar e the ability of FDDI-M to support synchronous traffic under different SEA schemes with that of FDDI. We use a new taxonomy of SEA schemes based on th e strategy used to partition the synchronous bandwidth, and present an anal ytical study of the timing properties of the FDDI-M protocol using the wors t case achievable utilization (WCAU) as the performance metric. The results show that while FDDI-M improves the WCAU values under one class of SEA sch emes, its performance under the other category of SEA schemes is mixed. We also perform extensive simulation to study performance of FDDI-M for MPEG v ideo traffic, and conclude FDDI-M does outperform FDDI significantly at hea vy load. The effect of SEA schemes under overload conditions is also shown to be relatively minor, with the local SBA schemes actually performing bett er than the global schemes. (C) 2001 Elsevier Science Inc. All rights reser ved.