共查询到17条相似文献,搜索用时 109 毫秒
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重尾ON/OFF源模型生成自相似业务流研究 总被引:23,自引:0,他引:23
因为传统模型没有考虑网络业务流量各种时间尺度都具有突发性,因此是不完善的,一系列的测量结果表明,网络业务流量显示自相似性,重尾分布ON/OFF模型能比较好地解释自相似业务流的产生原因,可以把LAN上的业务分解为多个活动(active)主机对之间的业务流,本文通过系统的仿真实验研究了重尾ON/OFF源模型生成自相似流的机理,并与理论结果进行了对比,而且补充了理论结果。 相似文献
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近年来,大量研究表明,网络业务流量呈现长相关、自相似的特性,采用ON/OFF源模型生成自相似流能够比较真实地反映现实网络中的业务流量。光突发包的汇聚算法是光突发交换的关键技术之一,利用ON/OFF模型生成的自相似流对几种典型的OBS汇聚算法进行研究。仿真表明,不同算法对自相似的影响不同。 相似文献
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使用泊松业务流模型对光突发交换网络进行性能分析不能准确地反映网络状态。该文从理论上对突发包长度进行了推导,对基于时间门限汇聚机制下突发包数据流自相似程度进行了计算机仿真测量,并利用自相似业务流模型对光突发交换网络中比较常用的LAUC和LAUC-VF调度算法进行了性能仿真。仿真结果表明:基于时间门限的汇聚机制能够有效地降低数据流自相似程度,数据流的自相似特性对LAUC算法的影响并不非常明显,但对LAUC-VF算法的性能则产生了比较严重的影响,其突发包丢失率较泊松流平均增加了近3个百分点。 相似文献
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一种基于最长队列预测的CICQ交换结构调度算法 总被引:1,自引:1,他引:0
CICQ(Combined Input Crosspoint Queued)是一种在crossbar交叉点加入少量缓存的交换结构,具有无需内部加速比及分布并行调度的特性。为了自适应网络环境中各种业务流量,提高在非均匀流量下的性能,该文提出了一种基于最长队列预测的高效CICQ交换结构调度算法RR-LQD (Round Robin with Longest Queue Detecting)。RR-LQD算法复杂度为O(1),具有良好的可扩展性;通过预测局部最长队列并尽力为其服务,保持调度中队列长度的均衡,能够适应各种非均匀流量的网络环境。仿真结果表明:在各种均匀和非均匀流量下,RR-LQD算法均能达到100%的吞吐量,并且具有优良的时延性能。该文使用FPGA芯片实现了RR-LQD算法仲裁器,能够满足高速、大容量交换结构的设计需要。 相似文献
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为了更深入地了解区分服务对网络QoS性能的影响,采用了能够真实反映网络流量特性的自相似业务模型进行分析,选取的模型是重尾ON-OFF叠加模型PowON-PowOFF;研究了自相似业务流在WFQ方案中对QoS参数的影响,并分析了该模型各参数对QoS性能的影响,为下一代网络采取相应机制克服突发业务的不利影响提供了依据。 相似文献
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网络流量建模是网络规划与性能评价的重要基础,传统的业务模型大多基于泊松模型和马尔可夫排队模型,只具有短程相关性,随着网络业务的不断研究发现,实际网络业务流在很长的时间范围内都具有长程相关性,即一种自相似性。本文采用RMD算法和Fourier变换法对网络流量的自相似模型-FBM模型进行了建模及仿真研究,生成了所需的自相似流量序列。然后分别采用R/S法和方差时间图法对其进行自相似参数检测。结果验证了仿真算法所产生的序列存在着自相似性,并同时对RMD算法和Fourier变换法的优缺点进行了分析。 相似文献
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输入排队Crossbar架构下的流量模型 总被引:2,自引:0,他引:2
本文基于IP包在路由器各端口到达流量的统计特性,建立了输入排队Crossbar架构下的流量模型,对IP包流量的平均到达速率、突发性和均衡性等流量特征进行了分类定义,给出了各自的充要条件.文中所讨论的突发度B和不均衡度U为到达流量提供了精细的计算粒度,从而为基于IQ-VOQ的调度算法性能评估提供了理论依据.与LAN的自相似模型、WAN的Poisson模型以及数据业务的ON/OFF模型相比,本文讨论的流量模型更适用于基于IQ-VOQ调度算法性能的精确评估,为路由器交换架构的工程设计提供了理论依据. 相似文献
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Mizuike T. Ito Y. Nguyen L.N. Maeda E. 《Selected Areas in Communications, IEEE Journal on》1991,9(1):37-47
A computer-aided approach to the planning of SS/TDMA network operation is proposed. SS/TDMA is a sophisticated satellite communication network based on an onboard switch matrix, whose operation planning is formulated as a large-scale scheduling problem. An overall planning and scheduling model is presented to deal with practical SS/TDMA systems, such as a two-frequency channel network and nondisjoint beam coverage. For systematic planning suitable for a computer-aided approach, the entire scheduling process is divided into several steps, for each of which an efficient mathematical model is proposed. A linear programming model is used for distribution of traffic on a beam-to-beam basis and the generated switching sequence is further refined by a model using the traveling salesman problem. Burst scheduling is carried out by the Bin packing algorithm and scheduling models for practical networks allowing transponder hopping and multidestination bursts. An algorithm called enhanced rescheduling is presented to further improve the scheduling capability of the existing methods. The performance of the proposed methods is demonstrated by simulation results 相似文献
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In this paper, we consider the problem of designing virtual topologies for multihop optical WDM networks when the traffic is self-similar in nature. Studies over the last few years suggest that the network traffic is bursty and can be much better modeled using self similar process instead of Poisson process. We examine buffer sizes of a network and observe that, even with reasonably low buffer overflow probability, the maximum buffer size requirement for self-similar traffic can be very large. Therefore, a self-similar traffic model has an impact on the queuing delay which is usually much higher than that obtained with the Poisson model. We investigate the problem of constructing the virtual topology with these two types of traffic and solve it with two algorithmic approaches: Greedy (Heuristic) algorithm and Evolutionary algorithm. While the greedy algorithm performs a least-cost search on the total delay along paths for routing traffic in a multihop fashion, the evolutionary algorithm uses genetic methods to optimize the average delay in a network. We analyze and compare our proposed algorithms with an existing algorithm via different performance parameters. Interestingly, with both the proposed algorithms the difference in the queuing delays, caused by self-similar and Poisson traffic, results in different multihop virtual topologies. 相似文献
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Control architecture in optical burst-switched WDM networks 总被引:27,自引:0,他引:27
Yijun Xiong Vandenhoute M. Cankaya H.C. 《Selected Areas in Communications, IEEE Journal on》2000,18(10):1838-1851
Optical burst switching (OBS) is a promising solution for building terabit optical routers and realizing IP over WDM. In this paper, we describe the basic concept of OBS and present a general architecture of optical core routers and electronic edge routers in the OBS network. The key design issues related to the OBS are also discussed, namely, burst assembly (burstification), channel scheduling, burst offset-time management, and some dimensioning rules. A nonperiodic time-interval burst assembly mechanism is described. A class of data channel scheduling algorithms with void filling is proposed for optical routers using a fiber delay line buffer. The LAUC-VF (latest available unused channel with void filling) channel scheduling algorithm is studied in detail. Initial results on the burst traffic characteristics and on the performance of optical routers in the OBS network with self-similar traffic as inputs are reported in the paper. 相似文献
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自相似网络通信量模型研究综述 总被引:7,自引:0,他引:7
越来越多的研究表明网络通信量不是Markov过程,而是在任意时间尺度上都具有突发特性,即自相似特性。描述网络通信量的数学模型主要有自相似和长相关结构。网络的某些参数服从重尾分布,从而导致网络通信量时间尺度上的突发特性。该文分析了传统网络通信量模型和性能分析的弊端,描述了新型网络通信量模型应该具有的基本特征。本文重点研究了网络自相似通信量相关的ON/OFF模型、用户访问概率模型和网络流量闭环模型,讨论了相关的研究方向,并总结了在研究网络通信量模型的过程中应该注意的原则和问题。 相似文献
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随着网络应用的发展,网络流量不断加大,对于网络应用系统的测试也占有越来越重要的地位.良好的网络流量模型能较为真实的反映网络的情况,并能给与应用系统更为全面的测试.根据统计学的结果表明,网络流量在时间上具有自相似性.因此,对自相似流量模型的研究十分重要.为了克服单机生成网络流量的不足,本文对于分形高斯噪声(FGN)模型的算法进行了改进,使其能够并行且高速的生成自相似样本.文中针对改进后的算法提出了分布式系统,并阐述了系统的整体结构和控制机制的设计与实现.本文的工作还包括实现了一个检测网络流量的检测端,并通过它来分析分布式系统所生成的样本.结果表明,本系统所生成的网络流量具有自相似性. 相似文献