缓冲交叉开关交换结构多播调度算法研究

高性能核心交换设备多播调度受到越来越多的关注.交叉开关结构下的多播调度方案或者性能较差，或者过于复杂，难于应用在高速交换场合.为此，提出一种面向多播的多输入队列缓冲交叉开关体系结构.将多播调度分解为信元分派、输入调度、输出调度3个可分布式并行执行的子问题，并设计了相应的调度算法，降低了算法复杂性.实验结果表明，交叉点缓冲区容量与输入队列数量对多播性能都具有很大的影响.在突发流量到达下，与单多播输入队列的体系结构相比，无论是采用O(1)复杂度的HA-RR-RR还是复杂度更高的调度算法，均能显著提高系统吞吐性能.

Multicast Scheduling in Buffered Crossbar Switches with Multiple Input Queues

The scheduling of multicast traffic in bufferless crossbar switches has been extensively investigated. However, all the proposed solutions are hardly practical for high capacity switches because of either poor performance or high complexity. A buffered crossbar switch with multiple input queues per input port for transferring multicast traffic is proposed. Under this architecture, the scheduler operates in three stages, namely cell assignment, input scheduling, and output scheduling. The scheduling algorithms with complexity from O(1) to higher are presented for different scheduling stages. Simulation results show that both the number of input queues and the size of crosspoint buffer can affect the throughput performance of a buffered crossbar under multicast traffic. However, under bursty multicast traffic, increasing the number of input queues gains more, no matter which algorithm is used, i.e. either HA-RR-RR with complexity O(1) or MMA-MRSF-LQF with higher complexity. This shows that the proposed scheme is more appropriate for high performance switches.