共查询到18条相似文献,搜索用时 140 毫秒
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一种基于门限的光突发交换受限偏射路由算法 总被引:6,自引:3,他引:6
提出了一种基于突发丢失门限的条件偏射路由算法(LDFD),该算法采用丢弃少量偏射的高优先级突发来保证偏射路由上较低优先级非偏射突发的服务质量(QoS)。当偏射的高优先级突发到达核心节点而该节点没有空闲数据信道时,就启用定义的偏射条件检测函数来判断是丢弃该突发还是允许其抢占非偏射的低优先级突发的资源,从而减少偏射突发与偏射路由上原有突发的竞争。仿真表明,该算法可以很好地控制偏射突发对偏射路由上正常流量的影响,并有效地提高整个网络的突发丢失性能。 相似文献
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支持业务均衡的OBS网络分布式回退偏射路由算法 总被引:1,自引:1,他引:0
突发竞争是引起光突发交换(OBS)网络丢包的主要因素之一,而作为一种有效的突发竞争解决方法的偏射路由,因其对光缓存器的性能和数量要求较低而备受关注。然而,现有偏射路由算法忽略了偏射业务对偏射路径上原有业务的影响以及业务被偏射后自身的成功传输率,同时也忽略由偏射引起的偏置时间不够的问题,致使OBS网络整体丢包率较高。为此,本文提出了一种支持业务均衡的分布式回退偏射路由算法(DBDF-LB),基本思路在于:从全网业务均衡出发,根据网络状态信息分布式的为偏射业务选择一条丢包率最小、跳数最短的路径;然后通过回退机制,利用网络资源来缓存突发包,从而补偿由偏射引起的额外偏置时间。与典型的最短路径偏射算法(SPDF)相比,DBDF-LB能有效降低丢包率约23~50%,而成功传输突发包所经历的平均跳数增加不到1跳。 相似文献
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偏射路由作为一种行之有效的光突发交换竞争解决机制而被广泛加以研究,文章提出了一种改进的基于奖惩机制的偏射路由算法,通过查找代表链路实时拥塞状况的奖惩列表,选择负载最小的链路对竞争的突发包进行偏射处理,与传统的固定最短偏射路由算法相比,本算法达到了均衡网络负载的目的。仿真结果表明:本文所提出的算法在突发丢失率及平均链路利用率方面性能都有所提高。 相似文献
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光突发交换是适合在当前技术条件下的新交换技术,它比电路交换灵活,带宽利用率高,又比光分组交换易于实现,将成为下一代光IP骨干网的核心技术。在光突发交换网络中,偏射路由算法是有效解决突发竞争、提高网络性能的一种重要措施。首先分析了发送端控制的偏射路由技术,在此基础上提出了一种基于阈值检测的偏射路由的改进算法。该算法通过跳数来控制无效偏射路由并通过有条件地丢弃偏射突发来保证正常突发的丢包率,从而减少偏射路由对网络负荷的影响,使整个网络的丢包率得到一定提高,改善网络性能。 相似文献
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可调参数偏射路由:一种光突发竞争解决算法 总被引:4,自引:1,他引:3
为解决当前偏射算法在偏射控制上的问题,提出了可调参数偏射路由(TPDR)算法。其主要思想为:以可调参数“偏射概率”来控制竞争突发的偏射,并在非线性规划下,从突发丢失概率(BLP)和路径长度意义上寻找较优的偏射路径。仿真结果表明:与直接丢弃、无条件偏射和有限偏射等传统偏射算法相比较,TPDR算法具有:既能有效改善网络总的BLP,也能为不同优先级突发提供服务质量(QoS)保证;同时,在一定程度上它可有效地减轻偏移时间赤字对偏射突发QoS保证的压力。 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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This paper proposes a contention resolution scheme considering multicast traffic in optical burst switching (OBS) networks.
In OBS networks, for unicast bursts, contention can be avoided by deflection routing. However, deflection routing cannot be
applied to multicast bursts because multicast bursts are transmitted along light-trees which are fixed, tree-shaped routes.
Therefore, the loss probability of multicast bursts is generally high. To resolve this problem, the proposed scheme introduces
an ingenious offset time assignment strategy which completely avoids contention of multicast bursts due to transmissions of
unicast bursts by strategically assigning additional offset times. Furthermore, in the proposed scheme, unicast bursts avoid
contention with deflection routing. Through simulation experiments, we show that the proposed scheme improves the loss probabilities
of both of unicast bursts and multicast bursts. 相似文献
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Optical burst switching (OBS) is a promising technology for bridging the gap between optical wavelength switching and optical
packet switching. Optical signal transmission quality is subject to various types of physical impairment introduced by optical
fibers, switching elements, or other network components. The signal degradation due to physical impairment may be significant
enough such that the bit-error rate of received signals is unacceptably high at the destination, rendering the signal to not
usable. In this article, based on earlier study, we study the burst-scheduling problem in OBS networks using two control packets
for each data burst, taking into account physical impairment effects. We propose a burst-scheduling algorithm that accommodates
incoming bursts by primary path routing, deflection routing, and burst scheduling. We design an admission control mechanism
to use network resources efficiently. At an OBS node, the proposed algorithm schedules bursts for transmission by searching
for available resources as well as verifying signal quality. Our simulation results demonstrate that the proposed algorithm
is effective in terms of reducing the burst-blocking probability. 相似文献
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One of the key problems to hinder the realization of optical burst switching(OBS) technology in the core networks is the losses due to the contention among the bursts at the core nodes.Burst segmentation is an effective contention resolution technique used to reduce the number of packets lost due to the burst losses.In our work,a burst segmentation-deflection routing contention resolution mechanism in OBS networks is proposed.When the contention occurs,the bursts are segmented according to the lowest packet loss probability of networks firstly,and then the segmented burst is deflected on the optimum routing.An analytical model is proposed to evaluate the contention resolution mechanism.Simulation results show that high-priority bursts have significantly lower packet loss probability and transmission delay than the low-priority.And the performance of the burst lengths,in which the number of segments per burst distributes geometrically,is more effective than that of the deterministically distributed burst lengths. 相似文献
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解决突发包的冲突问题是光突发交换网络的关键技术之一。为了降低突发包冲突时丢包率,提出了一种新型的基于信道分级和回退机制的冲突解决算法,该算法考虑突发业务优先级,将信道分成两个级别,有区别地对待高低优先级两种业务类型,并且增加了一部分回退信道作为保护和重发冲突数据包,能够有效地保证高优先级业务的传输可靠性。结果表明,当冲突发生时,网络能根据此时高低优先级业务量的比重配比,自适应地调节两个级别信道的数量,兼顾到低优先级业务的低丢包率,保证了较低的延时率。此算法相比以往的冲突解决算法具有较低的丢包率和相对小的延时率。 相似文献
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This paper proposes a dynamic burst discarding scheme for deflection routing in optical burst switching networks. In general, deflection routing is effective in lightly loaded situations, whereas it has a contrary effect in congested networks because deflected bursts accelerate network congestion. Thus deflection routing should be employed in lightly loaded networks. Incoming traffic, however, varies in time and location, so that temporal and/or local congestion cannot be avoided. Our proposed scheme resolves this problem in the following way. Each node autonomously detects congestion with local information, and bursts to be deflected are discarded in a probabilistic manner, based on the degree of detected congestion and the numbers of elapsed and remaining hops of those bursts. Simulation experiments show that when congestion happens temporarily, the proposed scheme reduces the burst loss probability, and it utilizes network resources efficiently when local congestion happens. 相似文献
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Optical Burst Switching (OBS) has been proposed as a promising switching technology for the next generation of optical transport networks. In this paper, we address the issue of how to provide proportional differentiated services in OBS networks. Firstly, a Dynamic Wavelength Selection (DWS) scheme is introduced to provide proportional differentiated services in bufferless OBS networks by dynamically assigning more and longer periods of wavelengths to high priority classes. This scheme can also utilize wavelengths efficiently because the wavelengths are shared among different classes. Next, a Delayed Burst Assignment (DBA) scheme is introduced, by which bursts of the high priority class are given a higher probability for reserving wavelengths by scheduling the bursts of the low priority class with a delay to provide quality of service (QoS) in OBS networks. The integration of these two schemes provides proportional differentiated services and improves the burst loss performance by giving the burst head packet (BHP) two opportunities of scheduling its data burst (DB). 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