Performance Aspects of the DQDB Protocol

Abstract Since 1987 the standards committee IEEE 802.6 is defining a new metropolitan area network based on a dual bus. It is called Distributed Queue Dual Bus (DQDB) and is highly compatible with the ATM switch technology. This paper deals with the evolution of the DQDB protocol from the performance point of view. First a review of the modifications and protocol enhancements for the Distributed Queuing Protocol is given. Based on detailed simulation models for the various protocols some results are presented, which depict the impact of the protocol modifications on the performance. Furthermore, two strategies of connecting an ATM link to a DQDB backbone are considered in order to reflect the performance behaviour of the DQDB system under asymmetric load conditions and to point out the influence of different priority classes.