Alternative Strategies for Improving the Fairness in and an Analytical Model of the DQDB Network

The unfairness problem of the distributed queue dual bus (DQDB) (IEEE Std 802.6) network is addressed, and several alternative solutions that can improve the network's fairness are proposed. Implementation methods that require simple additional hardware on top of the regular DQDB interface are outlined. Simulation examples are employed to compare the performance of the schemes and to gain insight into their characteristics. The performance is also compared with that of the original DQDB and the bandwidth-balancing DQDB. An analytical model of the DQDB network is developed. Some constrained assumptions for analytical tractability are used to obtain a Markov chain model for (an earlier version of) the entire DQDB network, the corresponding state-space explosion problem is highlighted. For reasonably small systems, the analytical model can predict an individual station's throughput and mean segment delay for known (possibly asymmetric) loading patterns. The model is verified via simulation. >

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