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Performance of IEEE 802.4--The Basis of MAP

Summers, Catherine; Weaver, Alfred
Summers, Catherine
Weaver, Alfred
Since the IEEE 802.4 token bus provides the lower layer of services of MAP, an under- standing of 802.4 and its performance aspects is prerequisite to understanding MAP. We present a brief tutorial on the IEEE 802.4 standard for token bus networks, followed by a performance analysis based upon simulation studies. We show how total bus capacity is divided among data throughput, token traffic, and propagation delays. We show the relative contributions of access delay and queueing delay to total message delivery time as functions of the network's offered load. The effects of message size and the number of active sta- tions on the message delivery times are also investigated. As the token cycle time increases beyond the Target_Rotation_Times for the non-Synchronous access_classes, service to the lower priority classes is curtailed; we present a formula which can be used to identify the offered load at which the transition (from normal to curtailed service) begins.
University of Virginia, Department of Computer Science, 1986
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