An approximate stochastic analysis of the packet‐pair probing technique for available bandwidth estimation

The packet‐pair probing algorithm for network‐bandwidth estimation is examined and an approximate model is proposed for predicting its behaviour. The model replaces the Poisson arrival process with a Gaussian distribution and resolves the queue‐size profile into two separate components: A transient component representing the buffer‐emptying process and an equilibrium component representing the return to steady‐state behaviour. Comparison with discrete‐event simulation results shows that the model is accurate in single‐hop paths when utilization is ?70% when the cross‐traffic packets are ?½ the size of the probe packets. When extended to two‐hop paths, the model remains accurate for smaller cross‐traffic packets ($\leq\frac{1}{10}-\frac{1}{5}The packet‐pair probing algorithm for network‐bandwidth estimation is examined and an approximate model is proposed for predicting its behaviour. The model replaces the Poisson arrival process with a Gaussian distribution and resolves the queue‐size profile into two separate components: A transient component representing the buffer‐emptying process and an equilibrium component representing the return to steady‐state behaviour. Comparison with discrete‐event simulation results shows that the model is accurate in single‐hop paths when utilization is ?70% when the cross‐traffic packets are ?½ the size of the probe packets. When extended to two‐hop paths, the model remains accurate for smaller cross‐traffic packets ($\leq\frac{1}{10}-\frac{1}{5}$ the probe‐packet size). Copyright © 2008 John Wiley & Sons, Ltd.     

Probing-based estimation of end-to-end available bandwidth

A new mechanism to estimate available bandwidth for multiple hop routes is proposed based on a minimally backlogging concept. Since the proposed mechanism can estimate the available bandwidth quickly and track it adaptively, a reasonable range of available bandwidth for a short time interval can be obtained using the mean and variance of the estimated available bandwidth. The performance of the proposed mechanism is verified by simulation in a multiple hop network topology.     

Toward accurate and efficient available bandwidth measurement

The packet-pair technique is the most popular end-based approach for bandwidth measurement. Most packet-pair based proposals use the fluid cross-traffic model to justify the design of their estimation techniques. However, real traffic is certainly not fluid. The consistency of the statistical packet-pair dispersion model in general bursty cross-traffic conditions has still not been fully justified in published research. Furthermore, we note that existing measurement techniques do not take account of the actual measurement variance, which means that they are often subject to significant fluctuations in accuracy. To achieve high accuracy and efficiency in available bandwidth measurement, we contribute analytical insights into packet-pair dispersion techniques by developing a queuing model to describe the impact of the cross-traffic on the packet-pair dispersion under bursty cross-traffic conditions. Based on this model, the consistency of statistical packet-pair dispersion measurement in general cross-traffic conditions is demonstrated and new approaches that help to detect and eliminate the elastic bias caused by measurement variance are presented. We show that the algorithm we developed works correctly on the Internet and offers more dependable measurement results than existing tools.     

Adaptive available bandwidth estimation for internet video streaming

In this study, an adaptive available bandwidth estimation approach that is suitable for Internet video streaming is developed. The algorithm exploits repetitive measurements and uses this redundancy to improve its video adaptation decision. The importance of available bandwidth estimation in Internet applications has recently increased particularly because of the heterogeneity of the network links. Many of the Internet paths may contain wired and wireless links in which loss may happen due to congestion as well as link errors. Hence, loss rate by itself is not a sufficient statistics for monitoring purposes. If the loss is due to congestion, video quality can then be decreased whereas if the loss is due to link error, no such action is necessary. Moreover, in video streaming, such an estimate can be used to determine the new video rate if the quality is to be increased. In our approach, active probing packets are used to estimate bandwidth in very short time duration. The novelty of our estimator is its adaptivity in the sense that the overhead caused by the estimator is automatically reduced when congestion builds up. The trade off is reduced accuracy. Such accuracy is not needed under congestion anyway and when things get back to normal, our estimator turns back to normal operation mode. We have integrated our algorithm into our video streamer and carried out experiments on both simulated and actual streaming applications on the Internet. The results indicate that our estimator algorithm increases streaming performance substantially.     

自适应的端到端可用带宽测量方法

提出了一种轻负载的、自适应的端到端可用带宽测量方法.在低负载链路下,计算探测包对距离增大的概率,结合输出探测包距离分布,得到可用带宽.在此基础上通过探测包输出包距离对称度区分链路负载情况,自适应地采用合适的可用带宽计算方法.仿真实验表明,相比之前方法,本方法测量时间少、准确性高、测量开销小.     

音频带宽扩展技术分析与展望

对音频带宽扩展中的非盲目式和盲目式高频重建技术进行了分析、对比,给出了非盲目式高频重建中的6种技术及盲目式高频重建中的4种技术的基本原理,并对它们各自的优劣性进行了评价,指出盲目式高频重建法将是未来频带扩展技术发展中关注和研究的热点.     

基于可延展带宽分配的卫星网络高可用性方案

随着IPTV等网络服务的蓬勃发展,以及地面互联网的接入与融合,针对空间信息网络的资源规划势在必行.同时,为了有效抵抗分布式拒绝服务(DDoS)攻击,可用性设计成为卫星正常运转的重要前提.提出了基于网络带宽资源分配的DDoS攻击防御体系,建立了有效的卫星网络拓扑结构模型,并引入了路由状态数据包的概念,设计了相应的卫星网络路由协议.在此基础上,阐述了具有延展性的网络带宽分配机理及其实现方式.根据安全性分析与实验评估结果,提出方案可在有效防范敌手攻击的同时,保障带宽资源的可延展分配,同时方案具备良好的实现性能.     

移动自组织网络可用带宽估计方法研究进展

首先分析了有线网络和无线网络带宽估计机制的区别,然后,在此基础卜给出了MANET可用带宽定义,并且从原理上分析了数据帧碰撞概率、回退时间以及信道空闲比例等对MANET中的可用带宽造成影响的因素,同时对各种参数的测量以及估计方法进行了详细介绍,最后展望了带宽估计的应用前景和研究趋势.     

Network selection based on available link bandwidth in multi-access networks

One of the important aspects of seamless communication for ubiquitous computing is the dynamic selection of the best access network for a multimodal device in a heterogeneous wireless environment. In this paper, we consider available bandwidth as a dynamic parameter to select the network in heterogeneous environments. A bootstrap approximation based technique is firstly utilized to estimate the available bandwidth and compare it with hidden Markov model based estimation to check its accuracy. It is then used for the selection of the best suitable network in the heterogeneous environment consisting of 2G and 3G standards based wireless networks. The proposed algorithm is implemented in temporal and spatial domains to check its robustness. The numerical results show that the proposed algorithm gives improved performance in terms of estimation error (less than 15%), overhead (varies from 0.45% to 72.91%) and reliability (approx. 99%)as compared to the existing algorithm.     

A survey and measurement-based comparison of bandwidth management techniques

This article gives a brief tutorial for bandwidth management systems; a survey of the techniques used by eight real-world systems, such as Class-Based Queuing (CBQ), Per-Flow Queuing (PFQ), Random Early Detection (RED), and TCP Rate Control (TCR); a compact testbed with a set of methodologies to differentiate the employed techniques; and a detailed black-box evaluation. The tutorial describes the needs for the three types of policy rules: class-based bandwidth limitation, session-bandwidth guarantee, and inter?intra-class bandwidth borrowing. The survey portion investigates how the eight chosen commercial?open-source real systems enforce the three policy types. To evaluate the techniques, the designed testbed emulates real-life Internet conditions, such as many simultaneous sessions from different IPs?ports, controllable Wide Area Network (WAN) delay and packet loss rate for each session, and different TCP source implementations. The performance metrics include accuracy of bandwidth management, fairness among sessions, robustness under Internet packet losses and different operating systems, inter?intra-class bandwidth borrowing, and Voice over IP (VoIP) quality. The black-box test results demonstrate that (1) only the combination of CBQ+PFQ+TCR can solve the most difficult scenario (multiple sessions competing for the narrow 20kb?s class); (2) the TCR approach may degrade the goodput, fairness, and compatibility even under slight packet loss rates (0.5 percent); (3) without PFQ, TCR and RED have limited ability to isolate the sessions (especially for RED); (4) the G.729 VoIP quality over a 125kb?s access link becomes good only after exercising MSS-clamping to shrink the packet size of the background traffic down to 256 byte.     

Analysis of some redundancy removal bandwidth compression techniques

Three redundancy removal bandwidth compression algorithms --the floating-aperture predictor, the zero-order interpolator, and the fan interpolator--are analyzed. Theoretical expressions are found for the mean and mean-square times between output samples of these devices when the input signal is a Markov process. These expressions are evaluated for the case in which the input is a first-order Gaussian Markov process, and the resulting output sampling rates and transmission bandwidths are compared to those required by a PCM system using uniform sampling and optimum linear filter interpolation. It is shown that, given sufficient a priori knowledge of the signal process, there is little to be gained by using these redundancy removal techniques in place of the PCM system. However, if the signal statistics are unknown, the use of these algorithms instead of PCM may provide a considerable bandwidth reduction.     

Assessment of dielectric charging in electrostatically driven MEMS devices: A comparison of available characterization techniques

The present work investigates the results of different characterization methods for the dielectric charging phenomenon applicable to metal–insulator–metal (MIM) capacitors and electrostatically actuated micro-electro-mechanical-systems (MEMS). The discharge current transients (DCT), thermally stimulated depolarization current (TSDC) and Kelvin probe force microscopy (KPFM) assessment methods have been applied to either MIM capacitors or electrostatic capacitive MEMS switches or both. For the first time, the KPFM methodology has been used to create a link between the results obtained from the DCT and TSDC techniques applicable for MIM and the results from MEMS switches. The comparison shows that the application of KPFM method to MIM and MEMS leads to the same results on the electrical properties of the dielectric material. This provides a novel powerful tool for the assessment of dielectric charging for MEMS switches using MIM capacitors which have much simpler layer structure. On the other hand the TSDC method reveals a continuous distribution of relaxation time constants, which supports the dependence of relaxation time constant calculated for MEMS on the duration of the observation time window.     

Rethinking available bandwidth estimation in IEEE 802.11-based ad hoc networks

This Letter rethinks the problems of available bandwidth estimation in IEEE 802.11-based ad hoc networks. The estimation accuracy is increased by improving the calculation accuracy of the probability for two adjacent nodes' idle periods to overlap.     

Analytical approach towards available bandwidth estimation in wireless ad hoc networks

Wireless Networks - Since 1999 IEEE 802.11 has become a dominating wireless technology for providing WLAN in both public and private places. The protocol has evolved with time and the current...     

Unicast probing techniques for estimation of shared loss rate

The paper introduces two new unicast active end‐to‐end measurement techniques, called the single–double unicast probing (SDUP) and the delay‐based unicast probing (DUP), to estimate the rate of losses which occurs on the shared network path of two flows. A comprehensive performance evaluation and a comparison between these two techniques and an existing one having the same objective, the striped unicast probing (SUP) (Proceedings of the INFOCOM 2001—The IEEE Conference on Computer Communications, No. 2, Anchorage, Alaska, U.S.A., 2001; 915–923), were carried out. We demonstrate that our proposed SDUP technique provides even better estimation accuracy compared to that of the SUP while it requires only one piece of measurement equipment at only one receiver instead of deploying units to both receivers. Furthermore, with only one sender and receiver pair we can measure not only one shared path, but any partial path that begins at the sender and is located on the sender–receiver path. We also show that while the DUP have the same accuracy as the SUP in the case of Drop‐Tail buffer management, the DUP is capable of measuring loss rates of RED buffers, which the other techniques do not work with. The SDUP and the DUP are less intrusive and cause less bursty traffic compared to the SUP. Finally, the adaptation of these techniques into passive measurements is also considered. Copyright © 2006 John Wiley & Sons, Ltd.     

End-to-end available bandwidth: measurement methodology, dynamics, and relation with TCP throughput

The available bandwidth (avail-bw) in a network path is of major importance in congestion control, streaming applications, quality-of-service verification, server selection, and overlay networks. We describe an end-to-end methodology, called self-loading periodic streams (SLoPS), for measuring avail-bw. The basic idea in SLoPS is that the one-way delays of a periodic packet stream show an increasing trend when the stream's rate is higher than the avail-bw. We have implemented SLoPS in a tool called pathload. The accuracy of the tool has been evaluated with both simulations and experiments over real-world Internet paths. Pathload is nonintrusive, meaning that it does not cause significant increases in the network utilization, delays, or losses. We used pathload to evaluate the variability ("dynamics") of the avail-bw in Internet paths. The avail-bw becomes significantly more variable in heavily utilized paths, as well as in paths with limited capacity (probably due to a lower degree of statistical multiplexing). We finally examine the relation between avail-bw and TCP throughput. A persistent TCP connection can be used to measure roughly the avail-bw in a path, but TCP saturates the path and increases significantly the path delays and jitter.     

A traffic control system for IEEE 802.11 networks based on available bandwidth estimation

To support Quality of service (QoS)‐sensitive applications like real‐time video streaming in IEEE 802.11 networks, a MAC layer extension for QoS, IEEE 802.11e, has been recently ratified as a standard. This MAC layer solution, however, addresses only the issue of prioritized access to the wireless medium and leaves such issues as QoS guarantee and admission control to the traffic control systems at the higher layers. This paper presents an IP‐layer traffic control system for IEEE 802.11 networks based on available bandwidth estimation. We build an analytical model for estimating the available bandwidth by extending an existing throughput computation model, and implement a traffic control system that provides QoS guarantees and admission control by utilizing the estimated available bandwidth information. We have conducted extensive performance evaluation of the proposed scheme via both simulations and measurements in the real test‐bed. The experiment results show that our estimation model and traffic control system work accurately and effectively in various network load conditions without IEEE 802.11e. The presence of IEEE 802.11e will allow even more efficient QoS provision, as the proposed scheme and the MAC layer QoS support will complement each other. Copyright © 2006 John Wiley & Sons, Ltd.     

Some techniques for evaluating the bandwidth characteristics of adaptive nulling systems

Some techniques for evaluating the bandwidth characteristics of adaptive nulling systems are presented. The system performance is categorized according to its antenna characteristics and the post-antenna channel tracking characteristics. The former tend to be radio-frequency (RF) percentage bandwidth dependent and the latter on the achievable component tolerances used to implement the channel (whether at RF or some lower intermediate frequency (IF)). Measured results are also presented for a seven-beam paraboloid reflector-type multiple-beam antenna (MBA), and the effects of feed-reflector multipath inherent in this geometry on the cancellation bandwidth is evaluated in detail.     

Analysis of bandwidth aggregation techniques for combined use of satellite and xDSL broadband links

The availability of multiple technologies to access the Internet is even more common in today's connectivity scenarios. As an example, smartphones make use of 3G/4G data technology but, when a Wi‐Fi access point is available, they switch from 3G/4G (which typically is a paid per volume service) to the wireless local access. The same principle is applicable for fixed access, when terrestrial ADSL or optical fiber and satellite technologies can be typically available in the same place. This paper focuses on the simultaneous availability of different access technologies with the capability to use them in combination, to offer better performance than the traditional single technology access.