Network Traffic Model for Industrial Environment

In this paper, a model of LAN traffic is presented. In the model, the most important components influencing the network traffic are taken into account. Namely, the transmission protocols and information buffering, operating systems, and queuing algorithms as well as user behavior in network applications are considered. The model is based on an "on-off" function. The network traffic observed at the physical layer is a superposition of many sequential and self-similar "on-off" processes. It has been shown that the self-similarity of the traffic, measured by the Hurst parameter, changes from almost 1.0 for very low frequencies to 0.5 for high frequencies     

Self-similarity in World Wide Web traffic: evidence and possiblecauses

The notion of self-similarity has been shown to apply to wide-area and local-area network traffic. We show evidence that the subset of network traffic that is due to World Wide Web (WWW) transfers can show characteristics that are consistent with self-similarity, and we present a hypothesized explanation for that self-similarity. Using a set of traces of actual user executions of NCSA Mosaic, we examine the dependence structure of WWW traffic. First, we show evidence that WWW traffic exhibits behavior that is consistent with self-similar traffic models. Then we show that the self-similarity in such traffic can be explained based on the underlying distributions of WWW document sizes, the effects of caching and user preference in file transfer, the effect of user “think time”, and the superimposition of many such transfers in a local-area network. To do this, we rely on empirically measured distributions both from client traces and from data independently collected at WWW servers     

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.     

一种基于小波的网络流量发生器设计

网络流量发生器在网络性能分析和协议实现中具有重要的作用。文章基于多分形小波模型，设计了一种自相似网络流量发生器。其中对随机数的生成、序列的截断、自相似序列的生成以及自相似流量的生成等主要设计部分进行了论述。与常用的基于分形布朗运动的模型的流量发生器相比，该发生器生成的流量具有更准确的自相似流量特性。     

网络业务流的自相似性

对通信网络的大量研究表明,网络业务本质是自相似的(相关函数上表现为长相关特性)。网络业务的统计自相似性主要是指在不同时间尺度上观测到的业务流量序列具有相同的统计特性。讨论了当前网络业务流的特性;分析了现有的自相似业务流模型。为在线测量网络中的高速业务流,根据实测时间序列数据建立合适模型提供了参考。     

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。     

无线Mesh网络流量自相似性研究

近年来,无线Mesh网络已成为一个倍受关注的研究领域.对无线Mesh网络流量特性的研究将有助于网络协议的研究、评估,以及网络结构的规划和建设.本文通过对无线Mesh测试网上采集的数据包进行统计分析,揭示了网络流量具有自相似的特性.同时,解释了无线Mesh网络流量自相似性是由网络中具有重尾分布特性的多个流叠加形成的,并通过仿真进一步分析了节点移动性对流量自相似性的影响.     

Swing: Realistic and Responsive Network Traffic Generation

This paper presents Swing, a closed-loop, network-responsive traffic generator that accurately captures the packet interactions of a range of applications using a simple structural model. Starting from observed traffic at a single point in the network, Swing automatically extracts distributions for user, application, and network behavior. It then generates live traffic corresponding to the underlying models in a network emulation environment running commodity network protocol stacks. We find that the generated traffic is statistically similar to the original traffic. Furthermore, to the best of our knowledge, we are the first to reproduce burstiness in traffic across a range of time-scales using a model applicable to a variety of network settings. An initial sensitivity analysis reveals the importance of our individual model parameters to accurately reproduce such burstiness. Finally, we explore Swing's ability to vary user characteristics, application properties, and wide-area network conditions to project traffic characteristics into alternate scenarios.     

网络流量的联合多重分形模型及特性分析

网络尺度行为的发现提供了用数学模型方法研究网络流量特性的可能性.本文基于连乘瀑布过程与K分布过程提出了联合多重分形(JMF)网络流量模型,该模型以尺度函数与矩因子的联合作为主要特征函数来研究网络流量的特性.理论分析及由实测网络流量数据的仿真结果表明,JMF模型可以较客观地同时描述网络流量短期分形行为与长期自相似行为,且实现复杂度小.其中尺度函数能够刻画时间尺度对流量特性的影响,矩因子描述了同一时间尺度上流量突发性的变化,二者的联合较好地描述了网络流量的短期行为,而模型的统计特性则刻画了流量的长期行为特征.     

3G网络与WLAN协同规划之探讨

分析了WLAN的技术特点、承载能力、应用场景;探讨了3G网络如何与WLAN协同规划;指出WLAN可作为3G网络的有效补充,和业主充分合作,在公共热点区域建设WLAN,以分流3G网络的高速数据流量,提升3G网络质量,改善用户体验;最后就如何充分发挥WLAN的作用提出了建议。     

Predictability of Aggregated Traffic of Gateways in Wireless Mesh Network with AODV and DSDV Routing Protocols and RWP Mobility Model

When evaluating the performance of routing protocols in wireless mesh network (WMN), we need deeper analysis from the aspect of network traffic complexity to show how traffic characteristics are influenced by routing protocols and node mobility. The predictability of network traffic can be used as one metric of complexity and can be analyzed by multi-scale entropy (MSE) method. With 20 different random waypoint (RWP) mobility scenarios and with destination sequenced distance vector (DSDV), a typical proactive protocol, and Ad hoc on-demand distance vector (AODV), a typical reactive protocol, the predictabilities of aggregated traffic of gateway in WMN are analyzed using MSE method to show how different routing protocols bear different mobility scenarios. The MSE results show that the aggregated traffic of gateway with DSDV is more difficult to be predicted than that with AODV for different mobility scenarios. The maxspeed parameter of RWP dominates the traffic predictability for AODV. Both of the pause time and the maxspeed parameters, have great influence on the traffic predictability for DSDV. The reasons lie in the behaviors of routing protocols, i.e., AODV has up-to-date paths while DSDV does not.     

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.     

高效能接入网络助电信运营商从互联网价值链获益

面对成为互联网流量管道供应商的尴尬,运营商需要构建一张具有以下特征的高能效接入网：高带宽（每用户达到50M甚至更高）、低延时、成本最优化的全IP宽带接入;采用可以同时满足家庭宽带用户、商业用户和移动基站回程等应用的统一融合的接入网平台;具有用户/业务/应用智能感知功能来保障正确的流量处理。高效能接入网将帮助运营商成为急速增长的高附加值互联网内容产业链的一部分。     

宽带卫星Mesh网多址接入信道预测分配方案研究

该文针对具有网状(Mesh)拓扑结构的宽带卫星通信网,研究了分布式控制多址接入信道分配策略。提出了一种基于自相似业务流量混沌预测的混合动态分配方案。利用OPNET软件建立了仿真系统,研究比较了信道分配周期、信道负载以及业务流自相似程度对几种方案性能的影响。仿真结果表明,对于采用地球同步轨道(GEO)卫星、低轨(LEO)和中轨(MEO)卫星星座的宽带卫星Mesh网,所提出方案在高信道负载条件下都具有明显的优势。     

Characteristics of WAP Traffic

This paper considers the characteristics of Wireless Application Protocol (WAP) traffic. We start by constructing a WAP traffic model by analysing the behaviour of users accessing public WAP sites via a monitoring system. A wide range of different traffic scenarios were considered, but most of these scenarios resolve to one of two basic types. The paper then uses this traffic model to consider the effects of large quantities of WAP traffic on the core network. One traffic characteristic which is of particular interest in network dimensioning is the degree of self-similarity, so the paper looks at the characteristics of aggregated traffic with WAP, Web and packet speech components to estimate its self-similarity. The results indicate that, while WAP traffic alone does not exhibit a significant degree of self-similarity, a combined load from various traffic sources retains almost the same degree of self-similarity as the most self-similar individual source.     

一种用于卫星网络的业务预测方法

针对卫星网络业务具有自相似的特点,介绍了一种基于集合经验模式分解的业务组合预测方法(EEMD)。该方法利用EEMD的分解特性,将具有自相似的网络流量分解成多个只具备短相关性的本征模态函数(IMF),这样便可使用传统的流量预测算法进行预测。文中使用人工神经网络与自回归滑动平均模型(ARMA)这两种方法进行预测。最后将多个本征模态函数(IMF)预测的结果相加作为原始信号的预测结果,实验证明此方法有更高的精度。为了迎合卫星实时性的需求,给出了硬件的框架,该框架采用DSP与FPGA相结合的构架实现连续数据的EEMD实时处理。     

T-MPLS网络中承载电路业务的最佳包长问题研究

该文基于ITU-T所制定的传送多协议标记交换标准,对客户端承载基于电路交换类型的业务进行了深入研究,比较了不同长度的电路业务分组对该业务延时和抖动的影响,并提出了一种动态改变电路业务封装包长的方案。该方案根据业务接收端数据的时延和方差统计情况,来计算一定范围内合适的电路业务净荷长度并反馈给源端的业务适配模块进行调整。为分析该方案的有效性,利用OPNET仿真软件搭建平台进行仿真。结果表明,该方案与固定封装包长方案相比在业务抖动特性和传输效率上具有明显的优势,能很好地适应电路业务的承载要求。     

自相似业务下共享通道保护WDM网络性能分析

该文利用随机中点置换-分形高斯噪声(RMD-FGN)方法生成自相似业务,并且利用分层图方法来记录WDM网络状态,提出了一种链路状态描述模型。对自相似业务下55 Mesh_Torus共享通道保护WDM网络性能进行了仿真。结果表明:当业务的自相似系数或方差变大时,也就是说业务的突发程度变大时,阻塞率变大,网络的性能下降。增加单纤波长数,可以降低阻塞率,提高网络性能。     

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。     

Analysis of a Campus-Wide Wireless Network

Understanding usage patterns in wireless local-area networks (WLANs) is critical for those who develop, deploy, and manage WLAN technology, as well as those who develop systems and application software for wireless networks. This paper presents results from the largest and most comprehensive trace of network activity in a large, production wireless LAN. For eleven weeks we traced the activity of nearly two thousand users drawn from a general campus population, using a campus-wide network of 476 access points spread over 161 buildings at Dartmouth College. Our study expands on those done by Tang and Baker, with a significantly larger and broader population. We found that residential traffic dominated all other traffic, particularly in residences populated by newer students; students are increasingly choosing a wireless laptop as their primary computer. Although web protocols were the single largest component of traffic volume, network backup and file sharing contributed an unexpectedly large amount to the traffic. Although there was some roaming within a network session, we were surprised by the number of situations in which cards roamed excessively, unable to settle on one access point. Cross-subnet roams were an especial problem, because they broke IP connections, indicating the need for solutions that avoid or accommodate such roams. This paper is revised and extended from our Mobicom02 paper.