自相似业务流复用特性分析

现有研究将复用的自相似业务流Hurst参数值确定为各个业务流中最大的H参数值，与业务流的其他性质无关，这一结论用于网络设备的设计不利于网络资源的有效利用。本文采用简单近似估算，并用分形布朗运动模型生成自相似业务流，彩用小波分析方法估计Hurst参数值。实验结果表明，由于复用合成业务流的渐近自相似的本质，在可以观测的时间尺度范围内业务流的Hurst参数比这理论预测值小；在一定的序列长度下，复用流的Hurst参数的不仅和最大Hurst参数业务流有关，还受到其它业务流，特别是业务流的方差系数所表现出的短时突发性影响，因此对合成业务流的自相似参数具有重要的影响。     

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。     

重尾ON/OFF源模型生成自相似业务流研究

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。     

Accurate approximation of cell loss probability for self-similartraffic in ATM networks

Recently, self-similar (or fractal) stochastic processes have been regarded as more accurate models of certain categories of traffic (e.g. LAN traffic) which will be transported in ATM networks. The authors propose a method for estimating the cell loss probability in an ATM multiplexer fed by a self-similar arrival process. The packet arrivals are generated by a fractional Brownian motion process and the service process is deterministic. The approach is based on theory for large deviations, and simulation tests show that it is more accurate than the existing approximation result     

自相似业务模型下的队列分析--大偏差技术

近年来对许多实际运行中的网络（局域网和广域网）的测量与分析证实：真实的网络业务具有统计上的自相似性而且是长相关的。传统的排队理论均假定业务是Poisson或Markovian,因此是短相关的,那里的队列分析方法对自相似业务模型是不适用的。大偏差技术是对自相似业务模型进行队列分析的有效方法。本文应用大偏差技术对以FARIMA为业务模型的队列系统进行了分析,结果证明：队列长度尾分布渐进为Weibullian分布,而且与模型的短相关结构无关。     

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.     

网络业务量的一种稳定多分形模型及其检验

目前网络业务量研究中有自相似和多分形两种主要的先验模型。自相似模型简洁,运用单一的H 指数来描述业务量特性,但它并不能完全表达业务量的信息;多分形模型更准确,但它运用函数形式的多分形谱来刻画信号,不便于实际分析。本文在无穷可分层叠的理论框架下提出了网络业务量的一种稳定多分形模型。运用小波变换方法,通过多个业务量记录的检验,证实此模型从尺度行为和边缘分布两方面都能准确刻画业务量。作为一般多分形过程的特例,该模型把多分形指数的表达式确定下来,并归结为4个参数的估计。     

自相似混合业务流的网络性能研究

针对传统业务流量模型的网络性能结论不能完全适用于多路自相似业务混合流量的智能电力通信网络,首先介绍基于分形布朗运动的单一自相似业务流模型,接着分析多路输入自相似业务的合成流量模型,然后研究多路输入自相似流的网络性能,最后给出智能电力通信网中4类通信业务的QoS要求,其中通信业务的QoS要求和多路输入自相似混合流的网络性能计算,可为智能电力通信网的进一步研究提供参考。     

基于分形漏桶整形器的通用处理器共享系统性能分析

为了分析自相似业务流对通用处理器共享（GPS）系统性能的影响,研究了GPS系统性能与业务流自相似参数等因素之间的关系.通过使用分形漏桶的包络曲线对进入GPS系统的自相似业务流进行整形,推导了利用自相似业务流作为输入的GPS系统的队列长度和时延统计上界.数值结果与分析显示,基于分形漏桶的GPS系统性能模型对自相似业务流具有较好的性能.     

Self-Similar Traffic in G/M/1 Queue Defined by the Weibull Distribution

The work considers a queuing system of the G/M/1 type that simulates service of self-similar traffic in a NodeB (e-NodeB) base station of a mobile operator. The feature of quality of service (QoS) characteristics estimation process for the self-similar traffic defined by the Weibull distribution is the solution based on the Laplace–Stieltjes transformation. The Laplace transformation for an infinite number of items under the Weibull distribution condition was found. It was shown that this series was equiconvergent to some convergence domain. The following QoS characteristics were obtained for the self-similar traffic: the average amount of time that a request spends in the system; the average number of requests waiting in the queue and the average queue length. The obtained results allowed to consider the real values of traffic serviced by a NodeB (e-NodeB) for their optimal deployment over a covered territory at the stage of frequency planning and operation of the 3G/UMTS and 4G/LTE networks.     

基于FBM模型的自相似流量建模仿真

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。     

自相似网络流量模拟的分布式系统的设计与实现

 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.     

Towards the formation of comprehensive SLAs between heterogeneous wireless DiffServ domains

Traffic patterns generated by multimedia services are different from traditional Poisson traffic. It has been shown in numerous studies that multimedia network traffic exhibits self-similarity and burstiness over a large range of time-scales. The area of wireless IP traffic modeling for the purpose of providing assured QoS to the end-user is still immature and the majority of existing work is based on characterization of wireless IP traffic without any coupling of the behaviour of queueing systems under such traffic conditions. Work in this area has either been limited to simplified models of FIFO queueing systems which do not accurately reflect likely queueing system implementations or the results have been limited to simplified numerical analysis studies. In this paper, we advance the knowledge of queueing systems by example of traffic engineering of different UMTS service classes. Specifically, we examine QoS mapping using three common queueing disciplines; Priority Queuing (PQ), Low Latency Queuing (LLQ) and Custom Queueing (CQ), which are likely to be used in future all-IP based packet transport networks. The present study is based on a long-range dependent traffic model, which is second order self-similar. We consider three different classes of self-similar traffic fed into a G/M/1 queueing system and construct analytical models on the basis of non-preemptive priority, low-latency queueing and custom queueing respectively. In each case, expressions are derived for the expected waiting times and packet loss rates of different traffic classes. We have developed a comprehensive discrete-event simulator for a G/M/1 queueing system in order to understand and evaluate the QoS behaviour of self-similar traffic and carried out performance evaluations of multiple classes of input traffic in terms of expected queue length, packet delay and packet loss rate. Furthermore, we have developed a traffic generator based on the self-similar traffic model and fed the generated traffic through a CISCO router-based test bed. The results obtained from the three different queueing schemes (PQ, CQ and LLQ) are then compared with the simulation results in order to validate our analytical models.     

Practical Time-Scale Fitting of Self-Similar Traffic with Markov-Modulated Poisson Process

Recent measurements of packet/cell streams in multimedia communication networks have revealed that they have the self-similar property and are of different characteristics from traditional traffic streams. In this paper, we first give some definitions of self-similarity. Then, we propose a fitting method for the self-similar traffic in terms of Markov-modulated Poisson process (MMPP). We construct an MMPP as the superposition of two-state MMPPs and fit it so as to match the variance function over several time-scales. Numerical examples show that the variance function of the self-similar process can be well represented by that of resulting MMPPs. We also examine the queueing behavior of the resulting MMPP/D/1 queueing systems. We compare the analytical results of MMPP/D/1 with the simulation ones of the queueing system with self-similar input.     

基于自相似业务模型的WCDMA接入性能分析

随机接入技术对WCDMA网络数据业务性能优化具有较大影响,文提出基于自相似业务模型的WCDMA接入技术并进行性能分析。仿真结果表明基于自相似业务模型的WCDMA网络数据业务接入性能与分形系数H值、网络负载G等参数有关。文章还提出了基于WCDMA的业务接入自相似均衡协议(TASEP),能明显改善WCDMA网络数据业务的接入性能。     

Edge node buffer usage in optical burst switching networks

Optical Burst Switching (OBS) combines the benefits of Optical Packet Switching and Optical Circuit Switching technologies to provide an efficient, yet cost effective, method for data transmission in an all-optical, bufferless, core network. While most studies on OBS has concentrated on the core OBS network, we contribute new studies for the buffer requirement of an OBS edge node. The buffer usage for OBS systems only arises in the edge nodes since they contain an array of assemblers which combines electronic data with a common destination into an OBS burst stream for transmission in an all-optical bufferless core network. Specifically, we present two analytical results for buffer usage in an OBS edge node: one for Poisson traffic and the other for self-similar traffic input. The results show that the aggregated traffic from many assemblers inherits the characteristics of the source input traffic. This means that the output traffic approaches Poisson if the input traffic is Poisson, and the output traffic remains self-similar if the input is self-similar. These results lead to the following important design issues when dimensioning buffer requirements in an OBS edge node: if the traffic input is Poisson, the M/G/m model is the model to use for obtaining the upper bound on buffer usage in an OBS edge node; and for the case of self-similar traffic, Brichet’s method can be used to provide the upper and lower bound.     

自相似业务量的流量控制研究

由于自相似性是宽带网络中业务量的一个普遍特性,因此在进行宽带网络管理和流量控制时必须考虑它所带来的影响。目前,有关基于自相似业务量的流控机制的研究已经引起了人们广泛地注意。一些研究表明自相似业务量表现出了与传统模型不同的排队特征。本文围绕业务质量保证和流量控制机制,具体研究和分析了业务量的自相似性质对业务量成形、用法参数控制和呼叫接纳控制等流量控制机制的影响,并得到了一些重要结论。     

LÉvy Flights and Fractal Modeling of Internet Traffic

The relation between burstiness and self-similarity of network traffic was identified in numerous papers in the past decade. These papers suggested that the widely used Poisson based models were not suitable for modeling bursty, local-area and wide-area network traffic. Poisson models were abandoned as unrealistic and simplistic characterizations of network traffic. Recent papers have challenged the accuracy of these results in today's networks. Authors of these papers believe that it is time to reexamine the Poisson traffic assumption. The explanation is that as the amount of Internet traffic grows dramatically, any irregularity of the network traffic, such as burstiness, might cancel out because of the huge number of different multiplexed flows. Some of these results are based on analyses of particular OC48 Internet backbone connections and other historical traffic traces. We analyzed the same traffic traces and applied new methods to characterize them in terms of packet interarrival times and packet lengths. The major contribution of the paper is the application of two new analytical methods. We apply the theory of smoothly truncated Levy flights and the linear fractal model in examining the variability of Internet traffic from self-similar to Poisson. The paper demonstrates that the series of interarrival times is still close to a self-similar process, but the burstiness of the packet lengths decreases significantly compared to earlier traces.      

基于分形整形器的GPS系统性能确定上界研究

为了精确求解以自相似业务作为输入的网络性能确定边界问题,在GPS(generalized processor sharing)系统入口处利用分形整形器对自相似业务进行调控,提出了基于分形整形器的GPS系统模型,基于确定性网络演算理论推导了使用自相似业务作为输入时该GPS系统的缓存队列长度、延迟、延迟抖动以及有效带宽等性能确定上界模型。数值结果表明,基于分形整形器的GPS系统性能确定上界模型对自相似业务具有较好的性能。