Nsv. Rao et al., AVERAGE WAITING TIME PROFILES OF UNIFORM DISTRIBUTED QUEUE DUAL BUS SYSTEM MODEL, IEEE transactions on parallel and distributed systems, 6(10), 1995, pp. 1068-1084
Citations number
41
Categorie Soggetti
System Science","Engineering, Eletrical & Electronic","Computer Science Theory & Methods
The Distributed Queue Dual Bus (DQDB) system consists of a linear arra
ngement of N nodes that communicate with each other using two contra-f
lowing buses, The nodes use an extremely simple protocol to send messa
ges on these buses. This simple, but elegant, system has been found to
be very challenging to analyze. We consider a simple and uniform abst
raction of this model to highlight the fairness issues in terms of ave
rage waiting time. We introduce a new approximation method to analyze
the performance of DQDB system in terms of the average waiting time of
a node expressed as a function of its position. Our approach abstract
s the intimate relationship between the load of the system and its fai
rness characteristics, and explains all basic behavior profiles of DQD
B observed in previous simulation. For the uniform DQDB with equal dis
tance between adjacent nodes, we show that the system operates under t
hree basic behavior profiles and a finite number of their combinations
that depend on the load of the network, Consequently, the system is n
ot fair at any load in terms of the average waiting times. We also sho
w that the main theme of the analysis carries over to the general (non
uniform) DQDB, By suitably choosing the inter-node distances, the DQDB
can be made fair around some loads, but such system will become unfai
r as the load changes, In the vicinity of a critical toad, the uniform
network runs into a state of instability, where its behavior fluctuat
es from one extreme to the other with small load variations, Our analy
sis is supported by simulation results.