自相似业务:基于多分辨率采样和小波分析的Hurst系数估计方法

新近对局域网和广域网上大量突发业务流量的监测结果表明，采用自相似建模表征业务到达过程的长时间相关特性具有较高精度，其中Ｈｕｒｓｔ系数是表征业务突发特性的重要参数，因此在一定的观察时间内对突发业务的Ｈｕｒｓｔ系数进行快速、准确的估计是高速宽带网络（如ＡＴＭ）实施流量控制和缓冲资源分配的前提。本文提出一种基于多分辨率采样和小波分析的Ｈｕｒｓｔ系数快速估计方法，对严格二阶自相似模型下Ｈｕｒｓｔ系数的估计     

On self-similar traffic in ATM queues: definitions, overflowprobability bound, and cell delay distribution

Recent traffic measurements in corporate local-area networks (LANs), variable-bit-rate video sources, ISDN control-channels, and other communication systems, have indicated traffic behaviour of self-similar nature. This paper first discusses some definitions and properties of (second-order) self-similarity and gives simpler criteria for it. It then gives a model of self-similar traffic suitable for queuing system analysis of an asynchronous transfer mode (ATM) queue. A lower bound to the overflow probability of a finite ATM buffer is obtained, as also a lower bound to the cell loss probability. Finally, the stationary distribution of the cell delay in an infinite ATM buffer is obtained     

Self-similar processes in communications networks

This paper reviews and discusses the known definitions and properties of second-order self-similar discrete-time processes and supplements them with some more general conditions of self-similarity. A model for ATM cell traffic is presented and self-similarity conditions of this model are found. This study is motivated by observations that traffic in many real communication networks is self-similar in nature     

Survey of traffic control schemes and protocols in ATM networks

The authors survey a number of important research topics in ATM (asynchronous transfer mode) networks. The topics covered include mathematical modeling of various types of traffic sources, congestion-control and error-control schemes for ATM networks, and priority schemes to support multiple classes of traffic. Standard activity for ATM networks and future research problems in ATM are also presented. It is shown that the cell-arrival process for data sources can be modeled by a simple Poisson process. However, voice sources or video sources require more complex processes because of the correlation among cell arrivals. Due to the effects of high-speed channels, preventive control is more effective in ATM networks than reactive control. Due to the use of optical fibers in ATM networks, the channel error rate is very small. The effects of propagation delay and processing time become significant in such high-speed networks. These fundamental changes trigger the necessity to reexamine the error-control schemes used in existing networks. Due to the diversity of service and performance requirements, the notion of multiple traffic classes is required, and separate control mechanisms should be used according to the traffic classes. The priority scheme is shown to be an effective method to support multiple classes of traffic     

基于LFSN自相似流量模型的随机突发边界分析

基于线形分形稳定噪声(LFSN)的网络业务流模型可以很好地描述流量的自相似和重尾特性,对这种模型的随机突发边界进行理论推导,得出较现有文献更为普遍的结论,尤其是其随机上界更为精确,因此在随机网络演算分析中有着重要意义.同时基于对一般LFSN过程的快速模拟,设计了一种独特的实验方法,得到突发边界随机分布的估计值,验证了理论推导的正确性.     

自相似业务流特性分析

针对ATM网络业务，分析了自相似业务的特性。在理论分析的基础上，构造了仿真模型，进行了计算机仿真，并给出了计算机模拟仿真结果。     

Multiple access control with intelligent bandwidth allocation forwireless ATM networks

Two major challenges pertaining to wireless asynchronous transfer mode (ATM) networks are the design of multiple access control (MAC), and dynamic bandwidth allocation. While the former draws more attention, the latter has been considered nontrivial and remains mostly unresolved. We propose a new intelligent multiple access control system (IMACS) which includes a versatile MAC scheme augmented with dynamic bandwidth allocation, for wireless ATM networks. IMACS supports four types of traffic-CBR, VBR, ABR, and signaling control (SCR). It aims to efficiently satisfy their diverse quality-of-service (QoS) requirements while retaining maximal network throughput. IMACS is composed of three components: multiple access controller (MACER), traffic estimator/predictor (TEP), and intelligent bandwidth allocator (IBA). MACER employs a hybrid-mode TDMA scheme, in which its contention access is based on a new dynamic-tree-splitting (DTS) collision resolution algorithm parameterized by an optimal splitting depth (SD). TEP performs periodic estimation and on-line prediction of ABR self-similar traffic characteristics based on wavelet analysis and a neural-fuzzy technique. IBA is responsible for static bandwidth allocation for CBR/VBR traffic following a closed-form formula. In cooperation with TEP, IBA governs dynamic bandwidth allocation for ABR/SCR traffic through determining the optimal SD. The optimal SDs under various traffic conditions are postulated via experimental results, and then off-line constructed using a back propagation neural network (BPNN), being used on-line by IBA. Consequently, with dynamic bandwidth allocation, IMACS offers various QoS guarantees and maximizes network throughput irrelevant to traffic variation     

PERFORMANCE ANALYSIS FOR ATM SWITCHING OF MIXED CONTINUOUS-BIT-RATE AND BURSTY TRAFFIC WITH SMOOTHING FUNCTION

Traditional packet switching networks have typically employed window-based congestion control schemes in order to regulate traffic flow. In ATM networks, the high speed of the communication links and the varied nature of the carried traffic make such schemes inappropriate. Therefore, simpler and more efficient schemes have to be proposed to improve the congestion control for ATM switching. This paper presents an exact performance analysis of ATM switching whose inputs consist of Continuous-Bit-Rate(CBR) and bursty traffic. The CBR traffic and bursty traffic are described by Bernoulli process and the Interrupted Bernoulli Process(IBP), respectively. Bursty traffic smoothing mechanism is analyzed. With the use of a recursive algorithm, the cell loss probability and the average delay for ATM switching of mixed CBR and bursty traffic are exactly calculated. Traffic smoothing could be implemented at a slower peak rate keeping the average rate constant or decreasing the average bursty length. Both numerical a     

Book reviews: a summary of multifractal traffic modeling

One of the most important discoveries about Internet traffic is the scaling phenomenon. Different from the traditional traffic pattern, primarily the Poisson model, this type of traffic shows a slowly decaying dependence structure and can be approximately characterized by a self-similar process. Multiscale behavior is a more complex version of self-similarity, indicating that the scaling property of the traffic process isn't uniform across multiple time scales and orders of statistics. It's often modeled with the multifractal process. "Multifractal Based Network Traffic Modeling" provides an accessible but somewhat narrow summary of the research on self-similar and multiscale traffic.     

THE ANALYSIS OF CELL LOSS RATES IN AN ATM MUX WITH LOSS PRIORITIES

The analysis of cell loss rates in an ATM Mux with loss priorities is an important problem in the-study of traffic control in ATM networks. In this paper, the loss rates of the cells with different priorities in an ATM Mux are analyzed by approximating the actual input process with two-state MMDP and fluid flow technique, and the analytical expressions of the relation between the loss rates and the buffer size are obtained. Simulation shows that the approach is sulliciently accurate for applications.     

Analysis of an ATM multiplexer under self-similar traffic

Recent empirical studies of the real traffic measurement show that the traditional traffic models cannot capture the character of long-range dependence of the traffic. And many computer simulations said that this character has large influences on the network performance. So fractal or self-similar models are more suitable to describe the modern traffic. But there is still little known about the performance of the multiplexer under self-similar traffic. In this paper, a quasi-self-similar traffic model (QSSP) is proposed. Using this model, the upper bond of the cell loss rate and multiplexing gain of the multiplexer are gotten when there are N i.i.d. QSSP inputs. If the sources have different parameters, an efficient numerical algorithm to get, this bond is proposed. Simulations indicate that our analysis is correct and accurate.     

突发性业务环境下周期性信元流通过ATM复接器的时延抖动

在输入ATM网络的业务源中,周期性信元流是很重要的一种.本文精确地分析了一个有限缓存的ATM复接器,其输入业务源由一路周期性信元流、多路随机性贝努利(Bernoulli)信元流和突发性两状态马尔科夫调制贝努利(MMBP)信元流构成.得出了该路周期性信元流的排队时延分布、时延抖动的自相关函数和功率谱.揭示了突发性业务环境下周期性信元流通过ATM复接器的时延抖动行为.计算机模拟验证了分析结果的正确性.     

含优先级机制的ATM Mux中的信元丢失率分析

含丢失优先级机制的ATM Mux中的信元丢失率分析是ATM网络流量控制研究中的一个重要问题.本文用两状态的MMDP近似实际输入过程,并采用流体流技术对不同优先级信元在ATM Mux中的丢失率进行了分析,得到了各类信元的丢失率与缓冲容量之间关系的解析式.模拟文验表明该方法足够精确,完全可以满足实际应用的需要.     

DELAY JITTER OF A PERIODIC CELL STREAM THROUGH AN ATM MULTIPLEXER IN A BURSTY TRAFFIC ENVIRONMENT

The periodic cell stream is a very important member among the input traffic sources in ATM networks. In this paper, a finite-buffered ATM multiplexer with traffic sources composed of a periodic cell stream, multiple i.i.d Bernoulli cell streams and bursty two-state Markov Modulated Bernoulli Process (MMBP) cell streams is exactly analyzed. The probability mass function of queuing delay, the autocorrelation and power spectrum of delay jitter for this periodic cell stream are derived. The analysis is used to expose the behavior of delay jitter for a periodic cell stream through an ATM multiplexer in a bursty traffic environment. The simulation results indicate that the analytical results are accurate.     

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.     

Measurement-based simulation model for TCP over ATM

Cell level analysis of ATM networks by means of simulation requires an accurate model for traffic sources. We present a simple model for TCP over ATM traffic sources in an ATM LAN, which captures the fundamental characteristics of the behaviour of tcp in this environment. The model was developed by extensive statistical analysis of numerous traffic traces recorded in an atm testbed. Simulated traffic generated by our model has roughly the same properties as observed in real traffic, even on the time scale of milliseconds. This makes it suitable for use by the analysis of various scheduling and congestion management algorithms.     

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。