Controlled Request DQDB: Achieving Fairness and Maximum Throughput in the DQDB Network

We propose an extension of the Distributed Queue Dual Bus (DQDB) protocol called Request Controlled DQDB that can achieves 100% channel utilization and has similar sharing properties as the bandwidth balancing method. Transmission of requests in the Request Controlled DQDB method is controlled by a mechanism that is similar to the one used in DQDB to transmit segments. The bandwidth balancing method is used to refrain an overloaded node from transmitting requests continuously. By balancing the number of requests transmitted we achieve fair sharing of data slots without wastage. A simulation study shows that the Request Controlled DQDB protocol solves the un-fairness problem in DQDB while maintaining 100% ef-ciency. The study also shows that DQDB networks using the Controlled Request method can be highly responsive to changes in the ooered load and have better message delay than networks that use Bandwidth Balancing .