A comparative performance analysis of distributed queue dual bus access control methods

Simulation results comparing several distributed queue dual bus (DQDB) medium access control methods are described. To address access fairness problems in the IEEE P802.6 proposed standard for DQDB metropolitan area networks (MANs), a method known as bandwidth balancing (BWB) was accepted as part of the draft proposed standard version 10 (D10). Another method, known as reservation request control (RRC), was reported earlier which showed that it also reduces these access fairness problems. It is shown that, under a wide range of operating conditions, RRC provides lower access time than BWB, typically an order-of-magnitude faster convergence to a fair operating point, and performance very close to an ideal round-robin queuing discipline. However, the additional RRC complexity and substantial differences between it and the current IEEE P802.6 proposed standard indicate that RRC is not justified for the near term. It is concluded that, with only minor added complexity, BWB provides the needed performance improvements for currently envisioned DQDB MANs