Bandwidth guaranteed multicast scheduling for virtual output queued packet switches

Multicast enables efficient data transmission from one source to multiple destinations, and has been playing an important role in Internet multimedia applications. Although several multicast scheduling schemes for packet switches have been proposed, they usually consider only short delay and high throughput but not bandwidth guarantees. However, fair bandwidth allocation is critical for the quality of service (QoS) of the network, and is necessary to support multicast applications requiring guaranteed performance services, such as online audio and video streaming. This paper addresses the issue of bandwidth guaranteed multicast scheduling on virtual output queued (VOQ) switches. We propose the credit based multicast fair scheduling (CMF) algorithm, which aims at achieving not only short multicast latency but also fair bandwidth allocation. CMF uses a credit/balance based strategy to guarantee the reserved bandwidth of an input port on each output port of the switch. It keeps track of the difference between the reserved bandwidth and actually received bandwidth, and minimizes the difference to ensure fairness. Moreover, CMF supports multicast scheduling by allowing a multicast packet to send transmission requests to multiple output ports simultaneously. As a result, a multicast packet has more chances to be delivered to all its destinations in the same time slot, and thus shortens its multicast latency. Extensive simulations are conducted to compare the performance of CMF with other existing scheduling algorithms, and the results demonstrate that CMF achieves the two design goals: short multicast latency and fair bandwidth allocation.