A traffic oriented pre-arbitrated slot reuse scheme in DQDB networks

Distributed queue dual bus (DQDB) networks are high speed metropolitan area networks specified by the IEEE 802.6 standard. They may serve as local subnetworks to gather high speed data for transmission over wide area B-ISDN networks or as backbones in mobile networks to connect wireless infrastructures. In these situations, DQDB networks will carry a predominant portion of isochronous traffic. Thus we are motivated to investigate how to efficiently support isochronous traffic via the pre-arbitrated (PA) access method in DQDB networks. We propose a new PA slot reuse scheme which can much improve DQDB networks' utilization via arranging isochronous connections to share octets in the PA slots. It is based on the idea of categorizing octets with octet types. A related problem of octet type selection is formulated and an algorithm is developed to solve the problem. Based on the algorithm's results, the proposed scheme is made efficient as well as traffic-oriented. Simulations are performed to show that the scheme is much better than the previous ones, in terms of utilization, drop rate and overhead. The new scheme is compatible with the current DQDB standard and can be implemented in the bandwidth manager and VCI server of a DQDB network.