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。     

SLDRT: A measurement technique for available bandwidth on multi-hop path with bursty cross traffic

End-to-end available bandwidth is of great importance as a metric that characterizes the network’s dynamic transmitting capability. Most estimation methodologies infer available bandwidth from the relationship between the input inter-packet gaps and those of the output. This paper analyzes the challenges brought by extending the measurement environment to the multi-hop path with bursty cross-traffic. Based on the analysis, a novel probing technique, self-loading decreasing rate train (SLDRT), is proposed. SLDRT measures the available bandwidth by using a single decreasing rate packet train. The special train can efficiently avoid bias caused by multiple sampling. Performance analysis via NS-2 simulations and PlanetLab experiments verify the effectiveness of our method under multi-hop path with the bursty cross traffic environment, and also show that SLDRT estimates available bandwidth more quickly, accurately, and with less measurement overhead than other existing techniques such as pathload and pathChirp.     

一种自负载降速率包列可用带宽测量算法

基于自负载周期流技术,提出一种采用降速率包列的可用带宽测量方法SLDRT(self-loading decreasing rate train),并全面分析了该算法在多跳网络、突发性背景流的环境下的性能.SLDRT采用单条包列即可实现对可用带宽的高速测量,具备单次采样、准确测量的特性,可通过调整递减因子等参数,提高测量精度,降低测量负载.理论分析和不同背景流场景下的实验结果表明:在多跳、突发性背景流下,SLDRT具有较强的健壮性;与pathChirp,Pathload算法相比,不仅测量精度优良,而且大量缩短了测量时间,减轻了因测量而引入的额外负载.     

Numerical analysis of the power saving with a bursty traffic model in LTE-Advanced networks

We analyze the power saving operation called Discontinuous Reception (DRX) with a novel bursty packet arrival model in 3GPP Long Term Evolution (LTE)-Advanced networks. Typical analytical studies on the power saving operations in wireless networks have been carried out under the assumption that an expectation of exponentially distributed packet arrival intervals stays unchanged. However, practical packet arrival rate may change depending on time or typical Internet services may incur bursty packet arrivals. In either case, we need to evaluate the performance of the DRX operation. For this purpose, we develop a more realistic traffic arrival model considering packets may arrive in a bursty manner under the DRX operation. We, then, analyze the performance of the DRX operation in terms of power saving efficiency and average queuing delay, respectively. The analytical results are validated via comparisons with simulation results.     

Available bandwidth estimation for the network paths with multiple tight links and bursty traffic

Available bandwidth (ABW) estimation is useful for various applications such as network management, traffic engineering, and rate-based multimedia streaming. Most of the ABW estimation methods are based on the fluid cross-traffic model. Inevitably, their estimation accuracy is limited in the network environments with bursty cross-traffic. In this paper, we apply packet trains (a series of probing packets) and a modified Ping to probe the ABW of a network path. Our proposed probing method can identify several tight links along a path and can infer their individual ABWs. The ABW estimation algorithm developed in this study, GNAPP, is also based on the fluid traffic model, but it can effectively filter out probing noise incurred in networks that carry bursty traffic. The algorithm employs not only the gaps of any two consecutive probing packets but also those of nonadjacent probing packets for ABW estimation. Thus, the number of samples for ABW estimation increases significantly without resorting to sending more probing packets and the estimation efficiency and accuracy are improved. In addition, two-stage filtering and moving averages are used in GNAPP for reducing estimation errors. Numerical results demonstrate that the estimation scheme based on GNAPP can achieve good accuracy even when the traffic is bursty and there are multiple tight links on the path being observed. Thus, it outperforms other well-known ABW estimation tools.     

基于车辆载带中继的路边单元突发业务分组调度最优策略

高速公路车联网场景中,路边单元(Roadside units,RSUs)可作为多种周边监测数据的汇入网关,其业务具有突发特性,且可通过移动车辆以"存储—载带—转发"方式传输到与骨干网络互联的RSU.针对RSU间业务传输问题,源RSU可根据实时业务到达率按需匹配资源,以应对业务突发性对分组端到端时延的影响.本文首先针对R...     

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。     

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。     

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。     

构建网络的新方法：基于环路的混合交换光网络*

为了能够更好地支持突发性数据业务,提出了一种新型网络交换结构——基于环路的混合交换光网络（cyclebased hybrid switching optical networks,CHSON）。该网络结合了光电路交换（OCS）和光突发交换（OBS）两种交换技术,不仅可以有效地降低网络节点的分组转发压力,而且能够较好地承载突发性数据业务。首先介绍了CHSON的网络结构和虚拓扑设计,然后阐述了节点设计及其执行流程。仿真表明,CHSON具有比OCS网络更低的丢包率,而且在丢包率和平均分组延时方面,CHSON较     

Controlling mean queuing delay under multi-class bursty and correlated traffic

This paper presents an adaptive queue management scheme to maintain queuing delay in a router at a required level based on a comprehensive analytical model under aggregated Internet traffic flows from various traffic classes. The proposed scheme uses a closed-loop feedback control mechanism to constrain the average queuing delay by regulating traffic arrival rate implicitly through a movable queuing threshold. A discrete-time queuing model is developed to derive the relationship between average queuing delays and queuing thresholds based on a traffic model that models aggregated Internet traffic through superposition of N MMBP-2 arrival processes. The queuing threshold is adjusted dynamically with reference to the relationship derived in the analytical model and also feedback of average queuing delay measurement. Packets are dropped dynamically with respect to the changes of queuing threshold and the packet loss events serve as implicit congestion indicators. Matlab is used to perform queuing analysis and simulation. Statistical evaluation is performed to show the efficiency and accuracy of the analytical and simulation results.     

一种基于包排队方式的网络路径可用带宽探测方法

对IP网络路径带宽的探测是目前网络研究领域的一个热点。本文提出了一种针对端到端的网络、基于包排队方式的双向双步长网络路径可用带宽的探测方法。该探测方法由时延监视和UDP发送两个进程组成,基于包的排队时延来获取路径的可用带宽,并通过采用双向双步长的方法来递增或递减UDP包的发送速率。所提出的探测方法可以明显减少探测次数和运行时间,从而降低探测带来的开销。实验结果显示,所设计的方法和技术是可行的和有效的。     

一种基于M/D/1排队模型的可用带宽测量算法

由于液体流模型不能反映实际背景流的突发性及包长分布,基于液体流模型的可用带宽测量技术在突发背景流及多跳链路下测量精度较低.因此,提出了一种基于M/D/1排队模型的高精度可用带宽测量算法FPU(five-packet-unit for available bandwidth measurement).该算法采用五包结构构...     

Remote detection of bottleneck links using spectral and statistical methods

Persistently saturated links are abnormal conditions that indicate bottlenecks in Internet traffic. Network operators are interested in detecting such links for troubleshooting, to improve capacity planning and traffic estimation, and to detect denial-of-service attacks. Currently bottleneck links can be detected either locally, through SNMP information, or remotely, through active probing or passive flow-based analysis. However, local SNMP information may not be available due to administrative restrictions, and existing remote approaches are not used systematically because of their network or computation overhead. This paper proposes a new approach to remotely detect the presence of bottleneck links using spectral and statistical analysis of traffic. Our approach is passive, operates on aggregate traffic without flow separation, and supports remote detection of bottlenecks, addressing some of the major limitations of existing approaches. Our technique assumes that traffic through the bottleneck is dominated by packets with a common size (typically the maximum transfer unit, for reasons discussed in Section 5.1). With this assumption, we observe that bottlenecks imprint periodicities on packet transmissions based on the packet size and link bandwidth. Such periodicities manifest themselves as strong frequencies in the spectral representation of the aggregate traffic observed at a downstream monitoring point. We propose a detection algorithm based on rigorous statistical methods to detect the presence of bottleneck links by examining strong frequencies in aggregate traffic. We use data from live Internet traces to evaluate the performance of our algorithm under various network conditions. Results show that with proper parameters our algorithm can provide excellent accuracy (up to 95%) even if the traffic through the bottleneck link accounts for less than 10% of the aggregate traffic.     

包对算法中的首包瓶颈链路后续排队现象

分析了基本的包过带宽测量算法，设计了一个该算法的理论证明过程。根据证明过程和理论分析，提出了另一种影响带宽估测结果的流量干扰现象－－首包瓶颈链路后续排队现象，在实际网络带宽测量中对这种现象做了分析和实验验证。最后针对这种流量干扰现象制定和实现了一种优化策略。     

一种端到端的有效带宽测量方法

有效带宽测量在服务器选择、覆盖网络路由选择和网络流量工程等方面有广泛的应用。通过分析发送频率与单向延时之间的关系,提出了一种基于多项式拟合的有效带宽测量方法PFAB（Polynomial Fitting for Available Bandwidth）。PFAB通过发送探测速率逐渐下降的探测包,并检测OWD的变化,推断探测速率和有效带宽之间的关系。当探测速率大于有效带宽时,OWD持续增长;在探测速率等于有效带宽时,OWD达到最大值,之后开始下降。NS-2仿真实验结果表明该方法能有效减少探测包数量,缩短探测时间,并且对网络造成的干扰小;在探测包瞬时频率变化较大时,可以快速到极值点,减少测量误差。     

BBR拥塞控制算法延迟及带宽探测优化

传统基于丢包的拥塞控制算法因为其高丢包率和引发缓冲区膨胀问题已经不能满足许多应用对网络性能的要求。谷歌提出的BBR(Bottleneck Bandwidth and Round Trip)算法以其抗丢包、高带宽利用率和低延迟等特性受到广泛关注与研究。但是BBR还存在排队延迟仍然较高、在RTT(Round Trip Time)较小环境下表现不佳、带宽探测不及时等问题。本文对BBR排队延迟和收敛性进行分析,进而提出改进方法:限制在外数据包数,并根据网络反馈适时减少拥塞窗口大小来降低延迟;在RTT较小环境下,将探测RTT阶段之前的带宽估计延续到探测RTT阶段之后;设置平稳状态最长保持时间及时退出平稳周期并进入探测周期。在NS3中的仿真实验结果表明,改进BBR降低了RTT及其抖动,提高了算法的收敛速度;能够在RTT较小环境下高效利用带宽;改进BBR能够显著提高长RTT流的带宽探测频率。     

链路带宽测量方法改进

链路带宽是网络性能分析，容量优化规划的基本指标，链路带宽测量常用的方法是VPS（variable packet size),但VPS具有误差累计和背景流量影响的缺陷，对VPS方法进行改进，提出和实现一个任意链路带宽测量方法PTVS（packet train with variable size)，消除逐跳测量造成的误差累计和背景流量影响，测量实验表明，PTVS具有精确，高效，迅速的特点，PTVS可测量的其他性能指标还包括RTT，单向延迟，丢包率，端到端瓶颈带宽以及链路利用率。     

A proportional feedback scheme for ATM networks

Available bit rate (ABR) service class is proposed by Asynchronous Transfer Mode (ATM) Forum to provide the “best-effort” services like traditional TCP/IP traffic. It is designed to make use of the remaining bandwidth not used by VBR and CBR. However, the bursty nature of ABR traffic makes it difficult to prevent buffers on ATM switches from overflowing. A number of schemes have been proposed for ABR traffic control. In this paper, a proportional scheme that is rate-based hop-by-hop flow control is proposed. A mathematical model is built to analyze the hop-by-hop flow control scheme. It is shown the scheme can utilize full bandwidth without any cell loss. It is also shown the scheme has low queuing delay and fast transient response.     

Per-stream loss behavior of ∑MAP/M/1/K queuing system with a random early detection mechanism

In this paper, the matrix-analytic approach is applied to explore the per-stream loss behavior of the multimedia traffic under RED scheme. We constructed a ∑MAP/M/1/K queuing model for the RED mechanism with multimedia traffic which follows a continuous-time Markovian arrival process (MAP). In addition to evaluating the long-term per-stream packet drop probabilities, we examine the bursty nature of per-stream packet drops by means of conditional statistics with respect to dropped periods and the probability that the queuing system stays in the dropped period. The dropped period corresponds to having more than a certain number of packets in router buffer; non-dropped period corresponds to the opposite. These performance measures describe the quality of service provided by the router to particular multimedia traffic streams in the presence of background multimedia traffic.