MIXED TIME-CONSTRAINED AND NON-TIME-CONSTRAINED COMMUNICATIONS IN LOCAL-AREA NETWORKS

It is well known that some time-token medium access protocols for loca l area networks (LANs) like the IEEE 802.4 token bus and the FDDI toke n ring can guarantee the medium access delay for time-constrained pack ets. However, a problem which has been largely overlooked is how these protocols can be made to provide a maximum throughput for nontime-con strained packets while guaranteeing the delay bound of time-constraine d packets. We first show how the parameters of the IEEE 802.4 token bu s and the FDDI token ring can be set to solve the above problem. Then, we design a new timer mechanism for the timed-token protocols which p rovides the highest guaranteed throughput of nontime-constrained packe ts among a set of medium access protocols called the token passing pro tocol, to which most of the existing non-contention LAN protocols belo ng. We present numerical examples to compare different protocols, all of which have shown the superiority of the proposed protocol to the ot hers.