Markovian Analysis of DQDB MAC Protocol

The Distributed Queue Dual Bus (DQDB) protocol or IEEE 802.6 has been accepted as the international standard for Metropolitan Area Networks (MAN). This paper describes a combined M/G/1 and Markov model for the steady state performance analysis of a DQDB network. In the analysis each station is considered independently, but not in isolation, thus avoiding the computational complexity which would otherwise be introduced by a large number of stations. Because of this, the proposed model is not restricted to trivially small networks frequently found in other analytical models. The model takes into account the relative position of a station on the network, the phase diierence between the two buses as well as the relative availability of QA-slots. Comparisons with our own simulation studies show that the analytical results lie well within acceptable error limits in all but exceptional cases. The eeect of various model parameters on network performance are also reported.