输入排队中抢占式的短包优先调度算法

Preemptive Short-Packet-First Scheduling in Input Queueing Switches

调度算法决定了输入排队交换结构的性能.本文根据Internet业务特征提出调度算法应保证短包的高优先级和低延迟.已有包方式调度中,长包信元的连续传输将造成短包长时间等待.为解决该问题,本文设计了一种低复杂度抢占式交换结构,并提出了相应的抢占式短包优先调度算法(P SPF) .短包优先可减小TCP流的RTT ,并由此提高TCP之性能.通过排队论分析和实际业务源模型下仿真可知P SPF取得短包近似为零的平均包等待时间,同时达到94 %的系统吞吐量.

Scheduling algorithms make a great impact on the performance of input queueing switches. From Internet traffic characteristics, it is pointed out that short packets should be guaranteed higher priority and lower delay in scheduling algorithms. In general packet-mode scheduling, short packets suffer from long waiting time due to the continuous transferring of cells of long packets. To solve this problem, we study the low-complexity preemptive packet-mode scheduling and propose the algorithm called preemptive short packets first (P-SPF). P-SPF improves the TCP performance by means of the fact that round-trip delays of TCP flows are greatly reduced. Both the analysis in queueing theory and the simulation results with respect to a real traffic model show that P-SPF can achieve almost zero average packet waiting time for short packets, while keeping a high overall throughput up to 94%.