A novel multicast mechanism for optical local area networks

In this paper, we propose a simple and efficient multicast scheduling algorithm, the Lookback Queue Access (LBQA) protocol for the employment in an asynchronous WDM optical star network. Network nodes use ALOHA based random access schemes to send their reservation packets over a common packet reservation control channel. A central traffic scheduler is allocated to coordinate message transmissions. The central scheduler carries out the LBQA scheme in real time in two phases. The first phase is to search (through input queues) for a candidate multicast message that can be sent, without partition, to all of its intended recipients. If phase 1 fails, the second phase is then activated to efficiently partition a multicast message into multiple transmissions. Performance results conducted via simulations have revealed that networks employing such a scheduling mechanism can exhibit superior network throughput levels and delay performances. To obtain sustainable high performances, we further propose an interconnected dual-star structure employed with the enhanced scheduling mechanism, the DS_LBQA algorithm. By using a simple heuristic approach, the DS_LBQA scheme is able to successfully exploit the inter data channels and properly utilize the wavelength reuse property of the intra data channels. Performance results have demonstrated the merits of deploying the DS_LBQA multicast algorithm in such a dual-star structure.