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为了降低光突发交换网络中突发包的丢失率、降低网络路径的阻塞率、减小突发包冲突的概率,提出了考虑优先级的突发包碎片可控合并重传算法。当网络中数据通信发生冲突时,该算法能根据优先级进行突发包的分片,核心节点将这一信息反馈给边缘节点,边缘节点根据突发碎片的优先级以一定的概率重传被丢弃的突发包分片;同时,针对由于多次重传导致的突发包碎片过多的问题,该算法还按照突发包碎片的优先级顺序进行碎片重组,大大降低了网络的阻塞率。结果表明,相比以往的冲突解决算法,此算法在网络业务繁忙时的数据丢比特率和网络阻塞率方面的改善作用有比较明显的优势。这一结果对光突发交换网络的网络的性能改善方面是有帮助的。 相似文献
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《AEUE-International Journal of Electronics and Communications》2014,68(1):44-50
In optical burst switching (OBS) networks, burst contentions in OBS core nodes may cause data loss. To reduce data loss, retransmission scheme has been applied. However, uncontrolled retransmission may increase network load significantly and data loss probability defeating the retransmission purpose. In addition, in a priority traffic existing OBS network, OBS nodes may apply different retransmission mechanisms to priorities bursts for quality-of-service (QoS) support. This study has developed a controlled retransmission scheme for prioritized burst segmentation to support QoS in OBS networks. Unlike previous works in the literature, we have set a different value to retransmission probability at each contention and propose a retransmission analytical model for burst segmentation contention resolution scheme. In addition, we have applied the proposed retransmission scheme to the prioritized burst segmentation for QoS support. We have taken into account the load at each link due to both fresh and retransmitted traffic, and have calculated the path blocking probability and byte loss probability (ByLP) for high-priority and low-priority burst to evaluate network performance. An extensive simulation has been proposed to validate our analytical model. 相似文献
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OBS网络中一种基于突发包优先级分割的可控重传方案 总被引:2,自引:2,他引:0
在光突发交换(OBS)网络中,突发包会由于竞争OBS核心节点输出端口的有限波长资源而发生冲突。突发包重传能够在一定程度上减少由于突发包在核心节点冲突而导致的数据损失,但重传次数的增加可能会加重网络负荷,反而增加数据丢失率。并且,在多业务存在的OBS网络中,重传方案需要能够实现区分服务以保证网络的服务质量(QoS)。据此,本文提出一种基于突发包优先级分割的可控重传方案,在实施优先级分割的同时,根据网络负荷赋予每次重传不同的概率,并对重传次数加以控制。最后,仿真分析了路径阻塞率和不同优先级业务的字节丢失率(ByLP,byte loss probability)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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Contention-Based Limited Deflection Routing Protocol in Optical Burst-Switched Networks 总被引:3,自引:0,他引:3
《Selected Areas in Communications, IEEE Journal on》2005,23(8):1596-1611
Optical burst switching (OBS) is a very promising switching technology for realization of an economical optical Internet. In OBS networks, when contention occurs at an intermediate switch, two or more bursts that are in contention can be lost because a forwarding path reservation is not made for a burst until a control message for the burst arrives. That is the reason why one of the critical design issues in OBS is finding ways to minimize burst dropping resulting from resource contention. In this paper, we propose and analyze a novel deflection routing protocol, which mitigates and resolves contention with significantly better performance as compared with techniques currently known in the literature. While several variants of the basic deflection routing scheme have been proposed before, they all lacked the ability to determine the alternate route based on clear performance objectives. In this paper, we present an on-demand deflection routing scheme, which sequentially performs the following: 1) based on certain performance criteria, dynamically determines if the burst should be deflection routed or retransmitted from source and 2) if the decision is to deflection route, then the same is done using a path that is based on minimization of a performance measure that combines distance and blocking due to contention. The proposed contention-based limited deflection routing scheme prevents injudicious deflection routing. Our simulation results show that the scheme proposed here has much superior performance both in terms of burst loss probability and increased network throughput. Through analytical and simulation modeling, a number of useful insights into the OBS network protocols and performance are provided. 相似文献
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The most important design goal in Optical Burst Switching (OBS) networks is to reduce burst loss resulting from resource contention.
Especially, the higher the congestion degree in the network is, the higher the burst loss rate becomes. The burst loss performance
can be improved by employing an appropriate congestion control. In this paper, to actively avoid contentions, we propose a
dynamic load-aware congestion control scheme that operates based on the highest (called ‘peak load’) of the loads of all links
over the path between each pair of ingress and egress nodes in an OBS network. We also propose an algorithm that dynamically
determines a load threshold for adjusting burst sending rate, according to the traffic load in a network. Further, a simple
signalling method is developed for our proposed congestion control scheme. The proposed scheme aims to (1) reduce the burst
loss rate in OBS networks and (2) maintain reasonable throughput and fairness. Simulation results show that the proposed scheme
reduces the burst loss rate significantly, compared to existing OBS protocols (with and without congestion control), while
maintaining reasonable throughput and fairness. Simulation results also show that our scheme keeps signalling overhead due
to congestion control at a low level. 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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Qiong Zhang Neal Charbonneau Vinod M. Vokkarane Jason P. Jue 《Photonic Network Communications》2011,22(3):299-312
For optical burst-switched (OBS) networks in which TCP is implemented at a higher layer, the loss of bursts can lead to serious
degradation of TCP performance. Due to the bufferless nature of OBS, random burst losses may occur, even at low traffic loads.
Consequently, these random burst losses may be mistakenly interpreted by the TCP layer as congestion in the network. The TCP
sender will then trigger congestion control mechanisms, thereby reducing TCP throughput unnecessarily. In this paper, we introduce
a controlled retransmission scheme in which the bursts lost due to contention in the OBS network are retransmitted at the
OBS layer. The OBS retransmission scheme can reduce the burst loss probability in the OBS core network. Also, the OBS retransmission
scheme can reduce the probability that the TCP layer falsely detects congestion, thereby improving the TCP throughput. We
develop an analytical model for evaluating the burst loss probability in an OBS network that uses a retransmission scheme,
and we also analyze TCP throughput when the OBS layer implements burst retransmission. We develop a simulation model to validate
the analytical results. Simulation and analytical results show that an OBS layer with controlled burst retransmission provides
up to two to three orders of magnitude improvement in TCP throughput over an OBS layer without burst retransmission. This
significant improvement is primarily because the TCP layer triggers fewer time-outs when the OBS retransmission scheme is
used. 相似文献
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Optical burst switching (OBS) is a promising technology which is able to well support bursty traffic and is also technically
mature. One critical issue in OBS networks is burst contention. Several methods have been proposed to solve contention such
as wavelength converters and fiber delay lines. Among those methods, routing is relatively cost-effective and technically
tractable and has been extensively researched. A framework for evaluation the strength of this method is presented in this
paper. As routing is a fundamental issue in optical networks and not only confined to OBS, the framework is applicable to
a class of connectionless and non-buffer all-optical networks. Through comprehensive analysis of the relation between the
total traffic load offered to the network and the traffic load on each link together with some mathematical skills, a lower
bound on the burst loss probability is figured out. Extending it by minimizing the lower bound over all reasonable topologies,
another lower bound is worked out. With the help of the two lower bounds, comprehensive prospect on the effectiveness of routing
and network topologies in reducing the burst loss probability is shown for the first time to the best of our knowledge. 相似文献
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《Lightwave Technology, Journal of》2009,27(24):5563-5570
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Biao Chen Jianping Wang 《Selected Areas in Communications, IEEE Journal on》2003,21(7):1071-1080
One promising switching technology for wavelength-division multiplexing optical networks is optical burst switching (OBS). However, there are major deficiencies of OBS. (1) The delay offset between a control message and its corresponding data burst is based on the diameter of a network. This affects network efficiency, quality-of-service, and network scalability.( 2) OBS adopts one-way resource reservation scheme, which causes frequent burst collision and, thus, burst loss. We address the above two important issues in OBS. In particular, we study how to improve the performance of delay and loss in OBS. To reduce the end-to-end delay, we propose a hybrid switching scheme. The hybrid switching is a combination of lightpath switching and OBS switching. A virtual topology design algorithm based on simulated annealing to minimize the longest shortest path through the virtual topology is presented. To minimize burst collision and loss, we propose a new routing algorithm, namely, p-routing, for OBS network. The p-routing is based on the wavelength available probability. A path that has higher available probability is less likely to drop bursts due to collision. The probability-based p-routing can reduce the volatility, randomness, and uncertainty of one-way resource reservation. Our studies show that hybrid switching and p-routing are complementary and both can dramatically improve the performance of OBS networks. 相似文献
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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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SuKyoung Lee LaeYoung Kim JooSeok Song David Griffith Kotikalapudi Sriram 《Photonic Network Communications》2005,9(3):347-356
In optical burst-switched networks, one of the most significant issues is contention resolution. There have been several deflection routing techniques as contention resolution. While contention is resolved by traditional deflection routing, it cannot guarantee that the control packet will reserve all the wavelengths successfully to the destination on the alternate path, especially when traffic load in a network is high. Therefore, in this paper, we propose a Deflection Routing with Virtual Wavelength Assignment (DR-VWA) algorithm in order to provide a higher resource guarantee for loss-sensitive traffic bursts. The proposed DR-VWA scheme (1) dynamically decides the alternate path with the least traffic load and (2) allows high-priority bursts in terms of loss to be assigned available wavelengths over the path virtually. The proposed scheme is evaluated through simulation, and it is shown that significant improvement with regard to burst loss and wavelength conversion cost can be achieved.This work was supported in part by the Korea Science and Engineering Foundation (KOSEF) through OIRC project and by the US National Communications System (NCS). 相似文献
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Delay-on-Demand: A Signaling Protocol to Reduce Blocking Probability in Optical Burst-Switching Networks 总被引:2,自引:0,他引:2
Optical burst switching (OBS) is emerging as one promising switching paradigm for the next generation optical networks. To support multiple services in burst-switching networks, the OBS paradigm should support some quality-of-service (QoS) provisioning. A major design issue in such networks is to reduce the blocking probability of the bursts arising due to resource contention at the intermediate core router. In this paper, we propose a signaling protocol which we call ‘Delay-on-Demand’ (OBS-DoD), to reduce blocking probability and support QoS in optical burst-switching networks. The proposed scheme guarantees that at least one of the bursts succeeds depending on its priority, propagation delay from the ingress router, and the burst-size when contention occurs at the core router. For this, we use a control packet to delay, in case of a contention, the transmission of bursts at the ingress router. We compare the performance of our proposal, by simulation, with an earlier proposed scheme, and show that the proposed OBS-DoD outperforms the earlier scheme in reducing the blocking probability. For simulation, we generated bursty traffic using an M/Pareto distribution. 相似文献