A SIMULATION STUDY OF.DQDB MAN

Abstract

Distributed Queue Dual Bus (DQDB) is the IEEE 802.6 standard for Metropolitan Area Networks (MANs). It is based on the } Dual Bus architecture. It uses a slotted transmission structure and is compatible with ATM based B-ISDN networks. A DQDB network supports two types of services, asynchronous and isochronous. A DQDB network is simulated using a process interaction approach. UNIX System V message queues are used to implement the dual bus and each node in the DQDB network is represented by a separate UNIX process. Both asynchronous and isochronous services are implemented for unipriority traffic. The performance of DQDB is evaluated on a per node basis. The parameters used for the performance are Bandwidth Sharing, Average Delay and Packet Loss. As the performance of DQDB is position dependent in the overload conditions, two fairness schemes, Bandwidth Balancing and Multiple Requests are implemented for unipriotity traffic and the performance of DQDB under these schemes is compared. Finally, a scheme for improving the channel utilization, by reusing the 'used slots' is implemented with the help of an additional node, called an Erasure Node.