System unfairness of DQDB in supporting multiple communities of interest

摘要

The DQDB (distributed queue dual bus) architecture has been adopted as the IEEE 802.6 Metropolitan Area Network standard. It is shown that the standard in its present form is still inadequate in dividing its available bandwidth between stations while supporting multiple communities of interest. In fact, the bandwidth balancing mechanism (BWB) introduced to overcome the unfairness of DQDB may actually worsen the fairness of the protocol. A modified version of the BWB mechanism called variable bandwidth balancing (V-BWB) which overcomes the inadequacies of DQDB during periods of heavy utilization is introduced.