一种基于pathchar算法的改进的网络端到端带宽测量方法

在网络端到端带宽的测量中,Pathchar测量算法是目前网络链路带宽测量算法中最成功的算法之一,但是也存在不能对反方向路径上各段链路带宽进行测量、背景流量和逐跳误差累积影响等问题.本文提出一种改进的基于pathchar的测量方法较好的解决了上述问题,提高了测量的精度和抗干扰性.     

一种速率自调节可用带宽测量算法

可用带宽是网络路由、网络服务质量、流量工程等方面的一个关键参数。目前很多研究方法都基于PGM模型和PRM模型,但这两种方法大都假设背景流量速率为固定比特流,不适用于低带宽的测试。提出一种端值自调节可用带宽测量算法,该算法充分考虑了低链路带宽的情况。通过对排队延时的处理、探测分组列速率端值自适应调节,实现了端到端可用带宽快速准确的测量。实验结果表明,该算法具有良好的测量效果,尤其在低带宽条件下较其它同类算法提高了测量准确性,加快了测量速度并减小了对网络的影响。     

带宽测量技术中背景流量特征和影响

端到端的带宽测量技术一直是研究的热点.现在有很多测量带宽的方法和工具,但是它们的测试环境特别是背景流量的设置,都是不相同的.首先调查了各种方法提出的测试环境;然后通过实验证明了不同的背景流量会影响到测试结果;最后提出了生成公平背景流量的新方法.该方法具有实际网络流量的特性,也便于在模拟环境中实现,可作为测量带宽算法的评估标准.     

一种测量任意链路可用带宽的方法

可用带宽测量对于网络行为分析、网络服务质量(quality of service,简称QoS)的验证等有很重要的作用.现有可用带宽测量工作主要集中在端到端路径可用带宽测量,仅提供路径上承压链路(tight link)的信息,而不能提供其他关键链路的信息.为此,提出一种新颖的链路可用带宽测量算法LinkPPQ(trains of pairs of packet-quartets used to measure available bandwidth of arbitrary links),它采用由四探测分组结构对构成的探测序列,能够测量网络中任意链路的可用带宽,并跟踪该链路上背景流的变化.在仿真环境和实际网络环境下研究了LinkPPQ 的性能.仿真结果表明,在几种不同背景流场景下,对于具有单狭窄链路的路径和具有多狭窄链路的路径,LinkPPQ 都能够对各个链路的可用带宽进行有效的测量.绝大多数情况下测量误差小于30%,且具有较好的测量平稳性.实验网的实验结果也表明,LinkPPQ 可以准确测量以下几种情况下的链路的可用带宽:a) 从容量为10Mbps 的链路准确地测量一条100Mbps 链路的可用带宽;b) 准确测量容量10 倍于紧邻其后狭窄链路的容量的链路的可用带宽;c) 准确测量具有多狭窄链路的路径上各狭窄链路的可用带宽.     

面向实时应用的可用带宽自适应测量方法*

设计了一种快速的自适应端到端路径可用带宽测量方法——AABw。它具有以下几个特点：针对背景流量突发性和负载状况,自适应地动态调整探测包串（probing packets train）的长度;改进了探测包串发送速率的调节方法,既保证了算法快速收敛的特点,又更能适用于背景流量突发的情况,提高了实时带宽测量的精确度;改进了判断单向延时趋势的算法。仿真实验表明,该算法能准确快速地测量出端到端可用带宽,适用于实时应用环境。     

使用自负载降速率探针包列的可用带宽测量方法

可用带宽是一条网络链路或路径的剩余带宽,该指标对网络流量工程以及速率敏感应用具有重要意义。现有的可用带宽测量技术大多基于单跳或者流体背景流量模型,在突发背景流及多跳路径下健壮性不足。现提出一种使用自负载降速率探针包列（SLDRT）技术的可用带宽测量方法。基于NS-2的仿真实验表明,SLDRT在多跳路径并基于非流体流量模型的网络环境下比另一重要测量工具pathChirp具有更高的准确性,并且平均测量时间小于30 ms,证明其可以满足高速、高精度的可用带宽测量需求。     

一种改进的基于包对理论的瓶颈带宽测量方法

通过详细分析背景流量对包对技术的影响,提出一种改进的基于包对理论的端到端路径瓶颈带宽测量方法,可以改善背景流量对包对技术的干扰,提高测量的精确度和速度.NS-2上的模拟实验结果表明,该方法是准确有效的.     

不同背景流量下TCP吞吐量的主动测量及分析

为了进行网络性能评估，在专用网络实验平台上开发了主动测量TCP吞吐量的工具NetThruput，并利用此工具在不同背景流量下测量端到端的TCP吞吐量；分析了TCP和UDP背景流量以及TCP连接的个数等因素对TCP吞吐量测量的影响；区分了TCP吞吐量和可用带宽。     

基于IPv6的园区网紧链路定位技术的研究

园区网网络可用带宽测量算法的研究是网络研究的首要问题,其中可用带宽又与紧链路是QoS的两个重要指标,在拥塞控制、流媒体应用,以及园区网各种应用服务等方面具有重要的意义.提出了一种在IPv6网络下紧链路定位的新方法,通过在可控制背景流量和实际的网络环境中进行实验数据统计分析,验证了在IPv6网络下紧链路定位方法的准确性、高效性和可行性.     

一种适用于IPv6的高效瓶颈带宽测量方法

提出了一种下一代网络的瓶颈带宽测量方法——IPv6-pckt-pr。该方法在OPNET仿真环境下，以自相似业务流为背景流量，给探测报文赋予相同的流标签，同时将其业务类别设置为最高级，通过发送不等长的探测包对测量端到端瓶颈带宽。分析与实验表明，该方法的测量结果准确度较好，分布比较集中，测量时间较短，并能有效减少测量带宽。     

基于非液体流模型的可用带宽测量精度

现有的可用带宽测量技术大多基于单跳链路和液体流模型,在突发背景流及多跳链路下测量精度较低。因此,分析了更符合网络实际的非液体流模型,提出了一种参数设置方法,减小了探测包长、探测速率、背景流速率及背景流包长等因素对测量精度的影响。在此基础上,改进了探测包对结构,该结构结合生存时间(TTL)值设置减小了探测包对间隔的测量误差,增强了带宽测量算法在多跳链路环境下的健壮性。仿真表明,基于非液体流模型的参数设置方法及改进的包对结构提高了可用带宽测量精度。     

Self-similar cross-traffic analysis as a foundation for choosing among active available bandwidth measurement strategies

Among the many active, available bandwidth estimation tools and methods that have appeared recently in the literature, none has emerged that is accurate and robust enough to function in different networking environments. One of the main reasons for this problem is the highly variable statistical nature of network traffic. We present a novel theoretical method for active measurement strategy analysis through self-similar process sampling analysis. The results obtained show a relationship between the main parameters in the measurement procedure, such as the number of samples, sample length, and sample distance. The study suggests that accurate measurements require the use of many samples and thus long measurement procedures, sometimes on the order of several minutes, depending on the amount of cross traffic. Additionally, through the analysis of several existing Internet packet traces, we recommend that the minimum single sample probe stream length must be longer than the average cross traffic interarrival. Following these findings, we propose a new method for available bandwidth estimation that has shown significant accuracy under different network setups.     

基于子路径可用带宽测量的紧链路定位方法

针对现有紧链路定位方法存在测量负载较大、测量精度不高等问题,提出一种性能优秀的端到端主动测量方法--PathLoche。该方法通过设计一种新颖的包列Loche,逐步迭代测量子路径的可用带宽,进而得到整条网络路径的可用带宽并确定紧链路的位置。仿真实验表明,PathLoche测量精度高、入侵度低。     

网络带宽测量影响因素研究

详细讨论现有网络带宽的测量方法,从内因、外因两方面,分析总结带宽测量的影响因素,着重对其中的数据包大小、背景流量以及网络延迟进行了研究.     

基于排队模型的包链测量方法特征分析

基于单跳路由器的排队模型,研究了受背景流量影响下的探测包链排队行为。随着背景流量影响程度的不同,分析得出无背景流量排队、短背景流量排队、长背景流量排队和多背景流量排队等四种具有不同时延变化分布特征的典型探测包链排队行为。仿真实验通过调整包链发送速率,模拟了不同的背景流量影响程度,发现探测包链的包时延变化有不同的分布特征,与分析的四种典型探测包链排队行为特征基本一致。     

Multi-layer MPLS network design: The impact of statistical multiplexing

The possibility of adding multi protocol label switching (MPLS) support to transport networks is considered an important opportunity by telecom carriers that want to add packet services and applications to their networks. However, the question arises whether it is suitable to have MPLS nodes just at the edge of the network to collect packet traffic from users, or to introduce also MPLS facilities on a subset of the core nodes in order to exploit packet switching flexibility and multiplexing, thus inducing a better bandwidth allocation. In this paper, we propose a mathematical programming model for the design of two-layer networks where MPLS is considered on top of transport networks (SDH or WDM depending on required link speed). Our models take into account the tradeoff between the cost of adding MPLS support in the core nodes and the savings in the link bandwidth allocation due to the statistical multiplexing and the traffic grooming effects induced by MPLS nodes. The traffic matrix specifies for each point-to-point request a pair of values: a mean traffic value and an additional one. Using this traffic model, the effect of statistical multiplexing on a link allows to allocate a capacity equal to the sum of all the mean values of the traffic demands routed on the link and only the highest additional one. We propose a path-based Mixed Integer Programming (MIP) model for the problem of optimizing the number and location of MPLS nodes in the network and the link capacities. We apply Lagrangian relaxation to this model and use the subgradient method to obtain a lower bound of the network cost. As the number of path variables used to model the routing grows exponentially with the graph size, we use an initially limited number of variables and a column generation approach. We also introduce a heuristic approach to get a good feasible solution. Computational results are reported for small size and real-world instances.     

Granular model of packet pair separation in Poissonian traffic

We introduce a theoretical model of packet pair separation based on a transient solution of the Takács integro-differential equation. We show that in addition to the parameters of the fluid approximation (physical bandwidth and the average cross traffic rate) a new parameter characterizing the granularity of the cross traffic is necessary. These three parameters determine the dynamics of the queue in the diffusive approximation and all important distributions and averages of the packet separation even in multi-hop scenarios (assuming independent cross traffic on different hops). The model describes correctly the data collected in simulations, laboratory and Internet experiments. The adjustable model parameters are the physical bandwidth, the available bandwidth and the weighted average of the packet size of the cross traffic. We show that an implementation of the theoretical results can be used to estimate such parameters in packet chirp type measurements and can be a good candidate for improved available bandwidth estimation.     

JitterPath: Probing Noise Resilient One-Way Delay Jitter-Based Available Bandwidth Estimation

Measurement of end-to-end available bandwidth has received considerable attention due to its potential use in improving QoS. Available bandwidth enables the sending rate to adapt to network conditions, so that packet loss, caused by congestion, can be significantly reduced before error control mechanisms are finally employed. To this end, we propose a probing noise resilient available bandwidth estimation scheme, called JitterPath, which is adaptive to both the fluid and bursty traffic models. Two key factors, one-way delay jitter and accumulated queuing delay, are both exploited to predict the type of queuing region for each packet pair. Then, the bottleneck utilization information included in the joint queuing regions is estimated and used to quantify the captured traffic ratio, which indicates the relationship between the probing rate and available bandwidth. The contributions of our method are as follows: 1) JitterPath can work without being restricted to fluid traffic models; 2) since JitterPath does not directly use the bottleneck link capacity to calculate the available bandwidth, it is feasible for use in a multihop environment with a single bottleneck; and 3) JitterPath inherently reduces the impact of probing noises under the bursty cross traffic model. Extensive simulations, Internet experiments, and comparisons with other methods were conducted to verify the effectiveness of our method under both single-hop and multihop environments     

Internet瓶颈链路带宽测量方法

网络测量是了解网络行为,进行网络控制,提高网络性能的重要环节和前提基础,其中,瓶颈链路带宽测量一直是网络测量的研究热点之一。该文分别讨论了基于可变分组大小技术和基于分组对(Packetpair)技术的网络瓶颈链路带宽测量算法,首先分析了两类算法的基本原理,然后仔细研究了算法的性能和存在问题,最后提出了进一步的研究方向。