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首先深入分析了TCP over OBS网络中造成TCP性能下降的各种原因.在此基础上,考虑将近年来提出的GAIMD算法与OBS网络的特点相结合,提出了一种改进的拥塞控制策略.该策略能在一定程度上改善OBS网络由于随机竞争丢包给TCP性能带来的负面影响. 相似文献
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光突发交换网络中的闭环竞争解析 总被引:2,自引:0,他引:2
为改善光突发交换网络(OBS)的性能,深入探讨了光突发交换网络中的闭环竞争解析,提出了OBS网络中的主动资源预留方案OBS—RED和显式竞争通知方案OBS—ECN。OBS—RED采用随机早期丢弃策略,即根据数据信道拥塞情况,随机早期地丢弃控制分组。OBS—ECN的实现需要OBS—RED的支持。在OBS—ECN中,不是随机丢弃控制分组,而是将这一信息显式地通知边缘节点,边缘节点再作相应的处理。OBS—RED与OBS—ECN的应用,有利于提高网络吞吐量和链路带宽资源利用率,大大减少数据突发的阻塞概率。 相似文献
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在光突发交换(OBS)基本概念的基础上,针对OBS网络,特别是OBS环网突发包竞争引起的突发包丢包等问题,介绍和比较了OBS网络中常用的突发包竞争解决办法.重点分析了几种适用于OBS环网的常用突发包竞争解决办法对网络吞吐量等主要性能的影响,指出了采用这几种竞争解决办法的网络的性能优劣,归纳总结了它们的优缺点. 相似文献
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根据OBS网络的结构和特点,分析了OBS网络核心节点的数据信道调度算法,提出了一种新的数据信道调度算法--最小间隙组调度(SGGS)算法,并详细讨论了该算法的具体实现.该算法将到达核心节点的控制包分组,然后将这一组控制包按数据包到达先后的次序调度数据信道,从而达到合理调度和使用数据信道,最终实现改善整个OBS网络性能的目的. 相似文献
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A major concern in optical burst-switched (OBS) networks is contention, which occurs when more than one bursts contend for the same data channel at the same time. Due to the bufferless nature of OBS networks, these contentions randomly occur at any degree of congestion in the network. When contention occurs at any core node, the core node drops bursts according to its dropping policy. Burst loss in OBS networks significantly degrades the throughput of TCP sources in the local access networks because current TCP congestion control mechanisms perform a slow start phase mainly due to contention rather than heavy congestion. However, there has not been much study about the impact of burst loss on the performance of TCP over OBS networks. To improve TCP throughput over OBS networks, we first introduce a dropping policy with burst retransmission that retransmits the bursts dropped due to contention, at the ingress node. Then, we extend the dropping policy with burst retransmission to drop a burst that has experienced fewer retransmissions in the event of contention at a core node in order to reduce the number of events that a TCP source enters the slow start phase due to contention. In addition, we propose to limit the number of retransmissions of each burst to prevent severe congestion. For the performance evaluation of the proposed schemes, we provide an analytic throughput model of TCP over OBS networks. Through simulations as well as analytic modeling, it is shown that the proposed dropping policy with burst retransmission can improve TCP throughput over OBS networks compared with an existing dropping policy without burst retransmission. 相似文献
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OBS网络中基于优先级的先分割后缓存冲突解决方法 总被引:4,自引:2,他引:2
为了有效地降低突发包的丢失率和保证OBS网络中不同优先级业务的服务质量,提出了一种基于优先级的先分割后缓存冲突解决方法。该方法通过在多波长信道系统的输出数据信道上设置光纤延迟线组来缓存被分割的冲突突发包。当冲突发生时,首先基于突发包的优先级和处理完毕时间进行"竞争突发包头部分割或者原突发包尾部分割"处理;无冲突部分进行交换或者直接在事先预留的输出数据信道上处理,冲突部分的分割突发包进行光缓存。仿真结果表明,多波长信道系统中,高优先级突发包的丢失率低于低优先级突发包的丢失率。同时该方法在一定程度上可以有效地减少端到端的传输时延和整个网络的丢包率,从而提高整个OBS网络的性能。 相似文献
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Optimized TQ-MAP: An Adaptive Mapping Mechanism to Guarantee the Coherence of QoS Support from IP to OBS 总被引:1,自引:0,他引:1
Yang Xiaolong Mao Youju Dang Mingrui Zhang Min Li Lemin 《Photonic Network Communications》2003,6(3):279-287
Because of its scalability, the idea of coarse packet classification can be utilized to OBS networks. However, due to the limited number of priorities supported by OBS networks, we usually adopt a many-to-one composite class burst (CCB) assembly technique, e.g., N:1-CCB. In this kind of technique, there are two aspects related to scalable QoS support, i.e., mapping relationship and assembly resource allocation. This paper simultaneously takes the two aspects into consideration, and proposes a novel assembly mapping mechanism, called Optimized TQ-MAP, in which the most important feature is adaptivity. Based on nonlinear programming and differential calculus, it allocates the burst assembling capacity between classes fairly, efficiently and differentially, and matches IP QoS requirement with OBS QoS capacity as possible as it can. The simulation results show that Optimized TQ-MAP is more adaptive, and can efficiently guarantee the coherence of QoS support from IP to OBS. 相似文献
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《Lightwave Technology, Journal of》2009,27(16):3370-3380