A comprehensive analysis of DQDB
Marco Conti, Enrico Gregori, Luciano Lenzini · European Transactions on Telecommunications · 1991
Abstract This paper reports on an extended simulation analysis of the asynchronous part of the DQDB MAC protocol. The analysis is divided into three parts. The first and second part deal with one priority level, while in the third part we analyze DQDB behavior with multiple priority level. In the first part we study DQDB inunderload conditionsi.e., when the offered load is lower than the medium capacity. Our results show that in underload, the access delay is not always as low as expected. In the second part we study DQDB inoverload conditions, i.e., when the offered load is higher than the medium capacity. Our results show that DQDB without the Bandwidth Balancing mechanism(BWB)is unfair and that the unfairness is dependent on the medium capacity and the bus length. When the BWB is enabled, DQDB fairness and performance, in the steady state, improve significantly. However, DQDB takes some time (depending on the BWB‐MOD value) to achieve the steady state during which the node quality of service is degraded. In the third part we show that the DQDB priority mechanism is not always effective.