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本文介绍了光突发交换的网络原理、网络结构和模块功能,结合国内外的研究成果,总结和讨论了光突发交换的资源预约机制,分析了它们的网络性能。 相似文献
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基于同波长光纤延迟线集光突发交换结构及其性能分析 总被引:2,自引:0,他引:2
由于光突发交换机制本身就避免了光缓存的使用,但是现实中,光突发包之间竞争以及提供优先级服务又依靠光纤延迟线来解决。为此,我们设计了应用光纤延迟线的光突发交换网络核心节点结构。为了避免光纤延迟线色散引起的突发包输入排队缓存偏移,在该结构中设计了同波长光纤延迟线集。采用了空分交换矩阵,避免了波长转换的需要。为了有效运行该交换结构,我们提出了输入排队与自适应光缓存调度算法,而该算法不仅仅适用于光突发交换,也适合于光纤延迟线得到普遍应用的光分组交换。该调度算法能够提供优先级服务,避免队头阻塞,对该调度算法建立了严格的理论分析模型,并进行了仿真。仿真结果表明,与传统的延迟线竞争解决方案相比,这一调度算法能够改善交换性能1到2个数量级,是利用光纤延迟线解决光突发交换中竞争问题的一个较佳方案。 相似文献
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光突发交换(OBS)技术由于结合了电的灵活处理和光的高速传输,成为构建下一代全光互联干线网最具前景的交换方式,其单向资源预留方式导致的突发包冲突是限制OBS走向实用的关键。基于突发包分段的光缓存冲突解决方法和基于突发包分段的波长转换冲突解决方法,首先通过对低优先级突发包进行分段解决冲突,然后对分段后冲突部分突发包进行光缓存或波长转换降低丢包率。对基于突发包分段的光缓存和基于突发包分段的波长转换两种冲突解决机制的性能进行了比较研究,仿真结果显示:两种机制都能够有效地降低整个网络的丢包率。当网络负荷较高时,采用基于突发包分段的光缓存方法对降低突发包的丢失率效果比较明显;当网络负荷较低时,采用基于突发包分段的波长转换方法能够更加有效地降低突发包的丢失率。 相似文献
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在光突发交换(OBS)网络中,突发竞争是影响网络性能的一个重要因素,因此如何有效地解决它,成了OBS网络非常重要的问题.在分析当前文献中的解决方案的优缺点后,提出了一种突发竞争解决方案的系统实现.该实现将光纤延迟线(FDL)时城缓存与波长转换器(TWC)波长变换、空城技术结合在一起,构造了一个基于前向转发缓存和反馈循环缓存的两级交换结构.最后从多方面对该系统实现的竞争解决有效性进行了性能分析和计算机仿真,结果表明:它在适当的业务强度(小于0.6)下,能有效改善突发丢失率和突发延迟;同时能降低系统所需的光器件数目. 相似文献
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随着电传送网技术向光传送网技术的演进.光层的联网能力越来越强,出现了几种光域上的交换技术:光线路交换/波长路由、光分组交换、光突发交换及为解决光分组在传送时出现丢失而重组时出现次序混乱等问题提出来的一种新颖的光分组流交换技术。下文将对这几种交换技术及其特点进行逐一介绍。 相似文献
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《Lightwave Technology, Journal of》2009,27(13):2315-2329
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In this article, an unreserved restoration solution for fast failure restoration in intelligent photonic networks is proposed. The unreserved restoration scheme is a real-time restoration technique that allows for utilizing network capacity dynamically and with full flexibility. However, it has the disadvantage of having a long restoration time as real-time redials are required after a failure is detected. The restoration time is crucial because long restoration times can result in data loss that is not expected, especially in high-speed networks. The proposed method targets reducing the aggregated optical cross-connect switching time to minimize real-time failure restoration time. With the proposed solution, in an event of failure, the restoration time can be reduced to times that are similar to those achieved in the reserved schemes. Common unreserved schemes have an inherent need for retries because the first try after failure detection and notification cannot always be guaranteed due to lack of network resource. In this paper, an enhanced implementation for the proposed solution is designed and described, which allows the features of the proposed solution to be fully realized and overcomes the inherent drawback of redundant OXC switching events for retries in common unreserved schemes. Through simulation experiments, it is shown that under a given network condition, the real-time path setup time for failure restoration required in the proposed solution can be improved by 68% compared with the common unreserved schemes. 相似文献
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错连就是在发生保护倒换时,一条业务被传送到另外的节点,而不是预定的节点并且没有纠正动作的情形.它是由波长重用和共享保护引起的.采用波长重用和共享保护的波分复用(WDM)环网在多点故障或节点失效时将产生错连.文章将就如何检测和阻止错连,提出一些见解. 相似文献
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The switchless all-optical network aims to provide a future single-layer, advanced transport architecture on a national scale. The single-hop, shared-access network employs time and wavelength agility (a WDMA/TDMA scheme), using fast tuneable transmitters and receivers, to set up individual customer connections through a single wavelength router, which is suitably replicated for resilience. While in a recent paper we reported the analysis and dimensioning of a switchless network assuming just the telephone traffic, we provide in this paper a new model, which contains innovative elements, and report original results assuming to deal with data traffic of two different types: constant bit rate (CBR) and variable bit rate (VBR). The innovation is based on the fact that the model considers more traffic flows with different traffic requirements (e.g., bandwidth, duration) as input to a group of time-slot connections on the same wavelength between two passive optical networks (PONs). We obtained analytical expressions of the main traffic characteristics (loss probability, throughput and overflowing traffic) both for the primary group of time-slots and for the secondary group of time-slots, to which the overflowing traffic streams enters.Moreover, we show that the innovative network structure, i.e., use of a passive wavelength router node (PWRN), works also perfectly with more different traffic streams.The analytical model presented in this paper has been compared with a simulation model. The comparison has revealed very good agreement. Relevant network cases are considered, and the dimensioning of the network in such cases is reported, in terms of the key network parameters, loss probability and throughput. 相似文献
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We consider wavelength routing networks with and without wavelength converters, and several wavelength allocation policies. Through numerical and simulation results we obtain upper and lower bounds on the blocking probabilities for two wavelength allocation policies that are most likely to be used in practice, namely, most-used and first-fit allocation. These bounds are the blocking probabilities obtained by the random wavelength allocation policy with either no converters or with converters at all nodes of the network. Furthermore, we demonstrate that using the most-used or first-fit policies gives an improvement on call blocking probabilities that is equivalent to employing converters at a number of nodes in a network with the random allocation policy. These results have been obtained for a wide range of loads for both single-path and general mesh topology networks. The main conclusion of our work is that the gains obtained by employing specialized and expensive hardware (namely, wavelength converters) can be realized cost-effectively by making more intelligent choices in software (namely, the wavelength allocation policy). 相似文献
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An Ant-Based Approach for Dynamic RWA in Optical WDM Networks 总被引:1,自引:0,他引:1
In this paper, we propose a new ant-based algorithm for the dynamic routing and wavelength assignment (RWA) problem in optical
WDM networks under the wavelength continuity constraint. Unlike conventional approaches, which usually require centralized
global network information, our new RWA algorithm constructs the routing solution in a distributed manner by means of cooperative
ants. To facilitate the ants’ foraging task, we adopt in our algorithm a probabilistic routing table structure for route selection.
The new algorithm is highly adaptive in that it always keeps a suitable number of ants in the network to cooperatively explore
the network states and continuously update the routing tables, so that the route for a connection request can be determined
promptly by the current states of routing tables with only a small setup delay. Some new schemes for path scoring and path
searching are also proposed to enhance the performance of our ant-based algorithm. Extensive simulation results upon three
typical network topologies indicate that the proposed algorithm has a very good adaptability to traffic variations and it
outperforms both the fixed routing algorithm and the promising fixed–alternate routing algorithm in terms of blocking probability.
The ability to guarantee both a low blocking probability and a small setup delay makes the new ant-based routing algorithm
very attractive for both the optical circuit switching networks and future optical burst switching networks 相似文献
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波分复用(wavelengthdivisionmultiplexing,WDM)提供了充分利用光纤通信带宽的有效途径,但是WDM中的独立波长数目十分有限,而普通的无源星形WDM网络中每个时刻每个波长只能有一个用户发送信息,难以支持大量用户。为此,本文提出了一种新型的WDM网络WRSN(wavelengthreusablestarnetwork)。在WRSN中每个时刻每个波长可以同时有两个用户发送信息。分析和模拟结果表明WRSN网络吞吐量高,分组时延小。具有很高的实用价值。 相似文献
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Weiwei Hu Rose Qingyang Hu Yi Qian 《International Journal of Communication Systems》2008,21(8):889-900
This paper proposes a new survivable traffic grooming wavelength retuning (STGWR) scheme in an all‐optical wavelength division multiplexing (WDM) network. In a dynamic WDM network, a connection may require a bandwidth less than a wavelength capacity. In addition, a connection should be protected against any network failures. Survivable traffic grooming (STG) can protect connections at subwavelength granularities. Wavelength retuning is a promising approach in an all‐optical WDM network, where a signal must remain on the same wavelength from its source to the destination, to alleviate the wavelength continuity constraint and reduce the connection blocking probability. Although both STG and wavelength retuning have attracted extensive research attentions nowadays, no effort has been made to combine these two promising approaches in one network. In this paper, we propose a wavelength retuning scheme with no service interruption in an all‐optical network with STG capability. The scheme allocates two routes, one for the active path and other for the backup path, in a shared mesh restoration manner to each incoming connection request and conducts wavelength retuning only on the backup path. Both wavelength retuning and mesh protection are done at the connection level instead of at the lightpath level. The simulation results of the proposed schemes are also presented. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献