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光突发交换网络中基于波长分集的QoS算法 总被引:1,自引:0,他引:1
光突发交换(Optical Burst Switching, OBS)被公认为是构建下一代光网络的有效交换技术。在OBS网络中有效地支持QoS (Quality of Service)是一个很重要的问题。该文从波长分集的思想出发,提出了几种适合OBS的QoS算法。这些算法可以根据各个优先级业务的变化情况,动态地调整各个优先级的业务使用的波长数目。通过仿真,并和已有算法相比,说明所提出的算法可以更好地提供区分服务,同时有效提高信道的利用率,降低整体的丢失率。 相似文献
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光突发交换网络基于优先级与突发包分割的光缓存方法 总被引:2,自引:1,他引:1
为了保证光突发交换(OBS)网络中不同优先级业务的服务质量(Qos)和有效地降低突发包的丢失率,提出了一种基于优先级与突发包分割的光缓存方法.该方法通过在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,基于突发包的优先级进行"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... 相似文献
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光突发交换(OBS)是近年来出现的一种新型光交换技术.OBS结合了光电路交换和光分组交换的优点,比电路交换更加灵活,而与光分组交换相比又提供了光层的统计复用能力且易于实现.OBS能提供高吞吐量、高带宽利用率和低时延,使其成为下一代城域网的有力竞争者.文章采用M/G/1排队模型,在限定条件下对不同优先级的突发包在OBS环网中的传输延迟进行了分析,最后给出了突发包在OBS环网中所经历的时延. 相似文献
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已有研究表明时隙光突发交换(TS-OBS)网络与常规OBS网络的性能基本一致.因此,在TS-OBS网络中有效地支持QoS(Quality of Service)是一个很重要的问题.文章从时隙分集出发,提出了一种适合TS-OBS网络的QoS算法,这种算法可以根据各个优先级业务变化情况,动态地调整各个优先级业务使用的时隙数目,能够在提供区分服务的同时更有效提高信道的利用率并降低网络的阻塞率. 相似文献
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《Lightwave Technology, Journal of》2009,27(16):3370-3380
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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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The design of OBS networks that guarantee QoS provisioning for different classes of traffic is a major topic under current
research. In this work we formulate a unified framework for studying QoS in OBS networks with a GMPLS-based control plane.
We use this framework in order to investigate two problems. First, the configuration of the parameters of an aggregation strategy
so that a given Forwarding Equivalency Class observes its corresponding QoS requirements. Second, we address the problem of
planning a whole OBS network given a series of QoS constraints for each one of the Forwarding Equivalency Classes in the network.
The presented QoS framework constitutes a valuable tool for studying QoS-related issues in OBS networks. 相似文献
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Performance analyses of optical burst-switching networks 总被引:6,自引:0,他引:6
Rosberg Z. Hai Le Vu Zukerman M. White J. 《Selected Areas in Communications, IEEE Journal on》2003,21(7):1187-1197
This paper provides a scalable framework for analysis and performance evaluation of optical burst-switching (OBS) networks. In particular, a new reduced load fixed point approximation model to evaluate blocking probabilities in OBS networks is introduced. The model is versatile enough to cover known OBS reservation policies such as just-enough-time, just-in-time, burst segmentation, and route-dependent priorities. The accuracy of the model is confirmed by simulation and the various policies are compared. 相似文献
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Wavelength Selection in OBS Networks Using Traffic Engineering and Priority-Based Concepts 总被引:4,自引:0,他引:4
《Selected Areas in Communications, IEEE Journal on》2005,23(8):1658-1669
A fundamental assumption underlying most studies of optical burst switched (OBS) networks is that full wavelength conversion is available throughout the network. In practice, however, economic and technical considerations are likely to dictate a more limited and sparse deployment of wavelength converters in the optical network. Therefore, we expect wavelength assignment policies to be an important component of OBS networks. In this paper, we explain why wavelength selection schemes developed for wavelength routed (circuit-switched) networks are not appropriate for OBS. We then develop a suite of adaptive and nonadaptive policies for OBS switches. We also apply traffic engineering techniques to reduce wavelength contention through traffic isolation. Our performance study indicates that, in the absence of full conversion capabilities, intelligent choices in assigning wavelengths to bursts at the source can have a profound effect on the burst drop probability in an OBS network. 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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H. Boyraz 《Optical Switching and Networking》2005,2(4):217-229
Optical Burst Switching (OBS) has recently been proposed as a candidate architecture for the next generation optical Internet. Several challenging issues remain to be solved to pave the way for the OBS vision. Contention arises in OBS networks when two or more bursts are destined for the same wavelength, and a wide variety of reactive contention resolution mechanisms have been proposed in the literature. One challenging issue in OBS is proactively controlling the traffic flowing through the OBS network so that the network does not stay in a persistent state of contention, which we call the congestion avoidance problem. Another challenging issue is the need for service differentiation, which is common today in electronically switched networks via the use of advanced buffer management and scheduling mechanisms. However, such mechanisms cannot be used in OBS networks due to the limited use, or total absence, of buffering. One of the popular existing approaches to service differentiation in OBS networks is the use of larger offset times for high-priority bursts which, however, increases the delays and may adversely affect application-level performance. In this paper, we propose a feedback-based rate control protocol for the control plane of the OBS network to both address the congestion avoidance and service differentiation issues. Using this protocol, the incoming traffic is dynamically shaped at the edge of the OBS network in order to avoid potential congestion in the burst-switched core. Moreover, the traffic shaping policies for the low and high priority traffic classes are different, and it is possible using the proposed protocol to isolate high-priority and low-priority traffic almost perfectly over time scales on the order of a few round-trip times. Simulation results are reported to validate the congestion avoidance and service differentiation capabilities of the proposed architecture. 相似文献