E-OBS网络中一种基于优先级的抢占窗口机制

摘要

In order to reduce burst loss probability and guarantee the quality of service (QoS) of optical burst switching (OBS) networks efficiently, a preemption window mechanism based on priority in emulated-OBS networks was proposed, in which a preemption window was set in the control channel of the emulated-OBS core routers to determine whether or not to allow high-priority bursts to preempt low-priority bursts. When competition occurs, the system estimates whether the arrival time of high-priority bursts corresponding to control bursts meets the preemption condition. If the preemption condition is satisfied, highpriority bursts are allowed to preempt low-priority bursts. Otherwise, preemption is not allowed. The theoretical analysis and the simulation experiment of this mechanism were carried out, and a series of data how the loss probability of the different priority bursts changing with the preemption window time in the different channel systems were obtained. Simulation results show that the mechanism can efficiently reduce the burst loss probability of high-priority bursts, and the burst loss probability of the highpriority bursts is much less than that of the low-priority bursts. The QoS of OBS networks is guaranteed by this mechanism. Hence, the scheme can efficiently improve the performance of OBS networks.%为了有效地降低突发包的丢失率和保证网络的服务质量,提出了模拟光突发交换网络中一种基于优先级的抢占窗口机制.该机制在模拟光突发交换核心路由器的控制信道上设置抢占窗口,以此来决定是否允许高优先级突发包抢占低优先级突发包.冲突发生时,系统判断高优先级突发包对应的控制包的到达时间是否满足抢占条件,如果满足抢占条件,则允许高优先级突发包抢占低优先级突发包;否则,不允许高优先级突发包抢占.对该机制进行了理论分析和模拟仿真实验验证,取得了在不同信道系统下,不同优先级突发包的丢失率随抢占窗口时间变化的一系列数据.结果表明,该机制能够有效地降低高优先级突发包的丢失率,并且得到的高优先级突发包的丢失率低于低优先级突发包的丢失率,从而很好地保障了网络的服务质量.这种方法能够有效地提高网络性能.