Iterative Multicast Scheduling Algorithm For Input-Queued Switch With Variable Packet Size

We consider an input-queued switch with a multicast-capable switch fabric. Existing scheduling algorithms mainly focus on packets with the same size, or cells. In practice, packets are of variable size. When they arrive at a switch, they will be segmented into cells for parallel switching. At outputs, cells will be reassembled back to packets before sending to the next hop. A scheduling algorithm should focus on maximizing packet performance rather than cell performance. To this end, packet-mode switching is adopted in this paper such that cells of the same packet are always sent in consecutive time slots, where each slot can accommodate one cell. To design an efficient scheduling algorithm for high-speed implementation, we follow the approach of iterative scheduling. The notion of preferred multicast relationship is then introduced to alleviate the head-of-line blocking problem. Based on it, an efficient single iteration algorithm is proposed. To the best of our knowledge, this is the first single iteration multicast scheduling algorithm with two-bit requests, i.e., a two-bit-single-iteration algorithm. Despite its simplicity, extensive simulation results show that our proposed algorithm provides excellent packet delay-throughput performance.