分析重尾ON/OFF源功率谱密度的TAM近似法

经过十年的研究，发现电信网络业务流量显示自相似和长相关性。传统模型不能很好的仿真网络特性，而重尾分布的ON／OFF模型能够很好地解释计算机网络业务流量的自相似性的形成机理，它的功率谱密度(PSD)成为判断其突发性的有效手段。本文在Laevens K的基础上，结合Harris CM提出的TAM方法，提出一种计算重尾ON／OFF源的PSD的TAM近似法，并通过MATLAB仿真得到PSD曲线，符合其长相关特性，证明了该方法的有效性。     

基于ON/OFF源模型的OBS汇聚算法研究

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。     

光突发交换网中流量特性分析与汇聚机制研究

文章对光突发交换(OBS)网络中的IP流量特性以及汇聚机制进行了深入的研究,通过引入ON／OFF源模型来模拟OBS网络中数据业务的自相似特性,通过对仿真进行分析,验证了ON／OFF理论模型的正确性,最后,利用合成的可控Hurst参数流量源,对几种典型的OBS汇聚算法进行了仿真分析,结果表明,这些汇聚算法对严格自相似性流量的长相关性并没有抑制效果,只是在短时间内对流量具有平滑作用．     

自相似网络几种不同模型的比较和分析

随着网络业务的多样化,多媒体数据流已成为网络数据流的主体,网络业务与早期相比有了很大变化,传统的网络理论已不适应当前的网络分析,因而提出了自相似网络建模的理论。目前已有多种方法应用于自相似网络建模中。文中着重介绍了2种类型4种建模方法,即开/关(ON/OFF)模型、分形布朗运动(FBM)模型、分形自回归滑动平均过程(FARIMA)模型和α稳定模型,并比较了它们的优缺点及其应用范围。     

自相似业务流模型的分析与比较

在研究通信网络的流量控制及网络性能时，业务流模型是一个重要的组成部分。本文分析了几种自相似模型的特点，并指出了这几种自相似模型的区别以及这些模型所适用的网络业务流。它对自相似业务的分析和处理具有一定的指导意义。     

自相似网络通信量模型研究综述

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。     

自相似业务环境下IP网络的排队性能分析

网络流量分析表明很多信息源的聚合会产生具有自相似特性的信息流，在自相似环境下分析IP网络的排队性能成为当前热点。文中采用具有Pareto分布的ON／OFF叠加模型作为输入业务，分析IP交换机缓冲区队列溢出概率，得到与实际网络相似的结论：溢出概率并不随缓存长度的增加而呈指数规律下降，其下降速度相对要慢得多。在自相似业务环境下，增加缓存长度并不能有效地降低丢失率。     

PowON-PowOFF模型对区分服务QoS性能影响的研究

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。     

面向大规模网络的聚集TCP流量模拟方法研究

为平衡大规模网络骨干网上TCP流量模拟的准确性和复杂度,提出模拟接入网出口处的TCP聚集流量,而不从单台主机或会话的层面进行流量模拟。从网络流量的自相似性出发,提出基于应用层和网络传输层自相似的TCP聚集流量模型:在应用层通过聚集多个服从Pareto分布的ON/OFF源模拟生成自相似流量,在网络传输层根据TCP机制实现对应用层流量的聚集传输控制。模拟结果显示,在流量负载比例、流量自相似性以及骨干节点丢包率等方面,模拟结果与采集自某互联网交换中心的实际数据吻合良好,表明了该模型的有效性。     

自相似网络业务流量的研究与实现

为了准确测试和评估网络交换设备及其调度算法的性能,一个能够真实反映实际网络业务流量特点的业务流量产生系统是十分必要的。近年来通过对大量网络业务流量的测量和分析,人们认识到网络业务流量呈现为长相关、自相似的特性,而非泊松过程。将这一特性和现有的业务流量描述模型相结合,利用具有重尾特性的概率分布函数:Pareto分布和截尾重尾分布,构造了在宏观上表现为自相似特性的业务流量模型。针对路由交换机构调度算法的性能测试的实际需要,建立了一个可用于软件测试的网络业务流量产生系统。     

Self-similarity through high-variability: statistical analysis ofEthernet LAN traffic at the source level

A number of empirical studies of traffic measurements from a variety of working packet networks have demonstrated that actual network traffic is self-similar or long-range dependent in nature-in sharp contrast to commonly made traffic modeling assumptions. We provide a plausible physical explanation for the occurrence of self-similarity in local-area network (LAN) traffic. Our explanation is based on convergence results for processes that exhibit high variability and is supported by detailed statistical analyzes of real-time traffic measurements from Ethernet LANs at the level of individual sources. This paper is an extended version of Willinger et al. (1995). We develop here the mathematical results concerning the superposition of strictly alternating ON/OFF sources. Our key mathematical result states that the superposition of many ON/OFF sources (also known as packet-trains) with strictly alternating ON- and OFF-periods and whose ON-periods or OFF-periods exhibit the Noah effect produces aggregate network traffic that exhibits the Joseph effect. There is, moreover, a simple relation between the parameters describing the intensities of the Noah effect (high variability) and the Joseph effect (self-similarity). An extensive statistical analysis of high time-resolution Ethernet LAN traffic traces confirms that the data at the level of individual sources or source-destination pairs are consistent with the Noah effect. We also discuss implications of this simple physical explanation for the presence of self-similar traffic patterns in modern high-speed network traffic     

Output power and SNR swings in cascades of EDFAs for circuit- andpacket-switched optical networks

A simple dynamic model of the erbium-doped fiber amplifier (EDFA) that includes self-saturation by amplified spontaneous emission (ASE) is used to analyze the power and signal-to-noise ratio (SNR) transients in wavelength division multiplexed (WDM) optical networks in which signals cross chains of EDFAs from source to destination. The model, which consists of solving sequentially one ordinary differential equation per amplifier, is used to (1) determine power and SNR excursions in the surviving channels along a chain of 35 EDFAs during isolated add-drop events in a 16-channel WDM circuit switching scenario and (2) run Monte Carlo simulations of the first five EDFAs of the same chain fed by burst-mode packet switching traffic on each of the 16 channels. Each packet source is modeled as an ON-OFF asynchronous transfer mode (ATM) source, with ON and OFF times having a heavy-tailed Pareto distribution. The aggregate source model is asymptotically self-similar, and well describes multimedia packet communications. The results are used to examine the influence of average network utilization and source ON-OFF time variance on the probability density function of signal power and SNR at each EDFA output. We demonstrate that self-similar traffic generates sizable power and SNR swings, especially at low network utilization. The simulations also indicate sizable broadening of the power and SNR density functions along the cascade of EDFAs, reaching levels in excess of 9 dBm and 4 dB for the power and SNR swings, respectively, at the 5th EDFA. The effect becomes more pronounced for longer EDFA chains. Such a large broadening may imply serious system impairments in burst-mode WDM packet networks     

Queue Analysis and Multiplexing of Heavy-tailed Traffic in Wireless Packet Data Networks

Recent research based on traffic measurements shows that Internet traffic flows have a fractal nature (i.e., self-similarity property), which causes an underestimation of network engineering parameters when using the conventional Poisson model. Preliminary field measurements demonstrate that packet data traffic in wireless communications also exhibits self-similarity. In this paper, we investigate the queuing behavior of self-similar traffic flows for data applications in a packet-switching single-server wireless network. The traffic is generated by an on–off source with heavy-tailed on periods and exponentially distributed off periods. We extend previous analysis of a relation among the asymptotic distribution of loss probability, traffic specifications, and transmission rate for a wireline system to a wireless system, taking into account wireless propagation channel characteristics. We also investigate the multiplexing of heavy-tailed traffic flows with a finite buffer for the downlink transmission of a wireless network. Computer simulation results demonstrate that assumptions made in the theoretical analysis are reasonable and the derived relationships are accurate.     

Traffic Capacity of UMTS System in Reverse Link

UMTS can be connected to data networks. So Internet traffic services such as WWW browsing, email, ftp, SMTP, etc should be handled by UMTS. Each of the traffic services has some specific properties but all of them obey a basic ON/OFF model. For a traffic service there is some unused (OFF) times between their transmitted packets which we may use them for other services to increase the traffic capacity of the network. In this paper we propose a new method on the Internet traffic evaluation in an interference limited UMTS-WCDMA system. In this method first we calculate ON and OFF time durations of the above traffic services based on the model presented in 3GPP then their activity factors. Secondly we introduce new capacity curves such as The Number of Web browsing users/Email users/ftp users/Telnet users and Fax users versus voice users. These are applicable in traffic planning for wireless systems.     

ATM网络中的ABR业务在不同ONOFF业务背景下的性能研究

本文比较研究了ＡＴＭ网络中的三种不同分布的ＯＮＯＦＦ源对ＡＢＲ业务性能的影响;周期性的ＯＮＯＦＦ源,长度为指数分布的ＯＮＯＦＦ源以及长度为Ｐａｒｅｔｏ分布的ＯＮＯＦＦ源．发现Ｐａｒｅｔｏ分布的ＯＮＯＦＦ源对ＡＢＲ业务的性能影响最大,此时需要更大的缓存器存放在ＶＢＲ业务的ＯＮ期间累积的ＡＢＲ信元．为了改善性能,我们对ＰａｒｅｔｏＯＮＯＦＦ源进行了平滑处理,还在理论上对所得实验结果作了解释．     

Study of the Effect of the Wireless Gateway on Incoming Self-Similar Traffic

It has been well established by now that high-speed wireline traffic exhibits self-similar behavior. Due to the important consequences of traffic self-similarity in network design, several studies have assumed that wireless traffic is also self-similar and looked at its effects on network performance. However, due to factors such as power limitations and the wireless channel, it is not straightforward that wireline traffic will remain self-similar as it enters the wireless network. This paper provides an analytical study of the propagation of traffic characteristics as wireline traffic is passed to the wireless network through a gateway. The analysis takes into account buffering and repacking operations performed at the gateway, and models for wireline traffic and the wireless channel. We consider two server models, an instant transfer model, and an energy-conserving one. We show that in most cases, in response to self-similar wireline traffic the gateway will produce self-similar wireless traffic. However, when the gateway operates under an energy-conserving mode and if it has a large buffer, wireline traffic such as non-real-time variable-bit-rate traffic will result in non-self-similar wireless traffic. We also study the delays of packets passing through a gateway that is fed by self-similar traffic and show that their survival function has an asymptotically power-law tail with index smaller than 2.