OBS网络中QoS优先级保证方案研究

Study on QoS priority guarantee scheme in optical burst-switched network

文章把信道分组和PPJET(Preemptive Prioritized Just Enough Time)协议以及光纤延时线三者结合使用,提出了一种新的QoS调度方案D-PPJET(Developed-PPJET)协议。在该协议下,高优先级数据包可以被动态地调度到任何可用的信道上去,而低优先级数据包只能在规定的部分信道上调度,并利用光纤延时线(FDL)缓存机制为未成功调度的突发包提供二次调度的机会,这样高优先级业务包调度成功的机会就大大增加,为高优先级业务提供了保证,同时还使得低优先级突发分组丢失率下降。结果表明它能够大大地改善整个网络突发包的丢失率、信道吞吐量及信道利用率。

A novel QoS schedule scheme algorithm based on the combination of the channel grouping, the PPJET and Fiber Delay Line named D-PPJET （Developed Preemptive Prioritized Just Enough Time） is proposed in this paper. In this algorithm, the high priority bursts can be scheduled onto any available channels, however, the low priority bursts can only be scheduled onto those pre-allocated partial channels. On the other hand, the Fiber Delay Line is used as the buffer, providing the second schedule chance for those bursts which is not scheduled successfully. The probability that successfully schedule high priority is much larger than the PPJET, the high priority operation can be guaranteed and the packets dropping ratio is much reduced. The resuits indicate that the algorithm can improve the ratio of packets dropping, the throughput and the channel utilization.