Performance analysis and network path characterization for scalable internet streaming

Delivering high-quality of video to end users over the best-effort Internet is a challenging task since quality of streaming video is highly subject to network conditions. A fundamental issue in this area is how real-time applications cope with network dynamics and adapt their operational behavior to offer a favorable streaming environment to end users. As an effort towards providing such streaming environment, the first half of this work focuses on analyzing the performance of video streaming in best-effort networks and developing a new streaming framework that effectively utilizes unequal importance of video packets in rate control and achieves a near-optimal performance for a given network packet loss rate. In addition, we study error concealment methods such as FEC (Forward-Error Correction) that is often used to protect multimedia data over lossy network channels. We investigate the impact of FEC on the quality of video and develop models that can provide insights into understanding how inclusion of FEC affects streaming performance and its optimality and resilience characteristics under dynamically changing network conditions. In the second part of this thesis, we focus on measuring bandwidth of network paths, which plays an important role in characterizing Internet paths and can benefit many applications including multimedia streaming. We conduct a stochastic analysis of an end-to-end path and develop novel bandwidth sampling techniques that can produce asymptotically accurate capacity and available bandwidth of the path under non-trivial cross-traffic conditions. In addition, we conduct comparative performance study of existing bandwidth estimation tools in non-simulated networks where various timing irregularities affect delay measurements. We find that when high-precision packet timing is not available due to hardware interrupt moderation, the majority of existing algorithms are not robust to measure end-to-end paths with high accuracy. We overcome this problem by using signal de-noising techniques in bandwidth measurement. We also develop a new measurement tool called PRC-MT based on theoretical models that simultaneously measures the capacity and available bandwidth of the tight link with asymptotic accuracy

Controlo de congestionamento em redes sem fios

Doutoramento em Engenharia ElectrotécnicaCongestion control in wireless networks is an important and open issue. Previous research has proven the poor performance of the Transport Control Protocol (TCP) in such networks. The factors that contribute to the poor performance of TCP in wireless environments concern its unsuitability to identify/detect and react properly to network events, its TCP window based ow control algorithm that is not suitable for the wireless channel, and the congestion collapse due to mobility. New rate based mechanisms have been proposed to mitigate TCP performance in wired and wireless networks. However, these mechanisms also present poor performance, as they lack of suitable bandwidth estimation techniques for multi-hop wireless networks. It is thus important to improve congestion control performance in wireless networks, incorporating components that are suitable for wireless environments. A congestion control scheme which provides an e - cient and fair sharing of the underlying network capacity and available bandwidth among multiple competing applications is crucial to the definition of new e cient and fair congestion control schemes on wireless multi-hop networks. The Thesis is divided in three parts. First, we present a performance evaluation study of several congestion control protocols against TCP, in wireless mesh and ad-hoc networks. The obtained results show that rate based congestion control protocols need an eficient and accurate underlying available bandwidth estimation technique. The second part of the Thesis presents a new link capacity and available bandwidth estimation mechanism denoted as rt-Winf (real time wireless inference). The estimation is performed in real-time and without the need to intrusively inject packets in the network. Simulation results show that rt-Winf obtains the available bandwidth and capacity estimation with accuracy and without introducing overhead trafic in the network. The third part of the Thesis proposes the development of new congestion control mechanisms to address the congestion control problems of wireless networks. These congestion control mechanisms use cross layer information, obtained by rt-Winf, to accurately and eficiently estimate the available bandwidth and the path capacity over a wireless network path. Evaluation of these new proposed mechanisms, through ns-2 simulations, shows that the cooperation between rt-Winf and the congestion control algorithms is able to significantly increase congestion control eficiency and network performance.O controlo de congestionamento continua a ser extremamente importante quando se investiga o desempenho das redes sem fios. Trabalhos anteriores mostram o mau desempenho do Transport Control Proto- col (TCP) em redes sem fios. Os fatores que contribuem para um pior desempenho do TCP nesse tipo de redes s~ao: a sua falta de capacidade para identificar/detetar e reagir adequadamente a eventos da rede; a utilização de um algoritmo de controlo de uxo que não é adequado para o canal sem fios; e o colapso de congestionamento devido á mobilidade. Para colmatar este problemas foram propostos novos mecanismos de controlo de congestionamento baseados na taxa de transmissão. No entanto, estes mecanismos também apresentam um pior desempenho em redes sem fios, já que não utilizam mecanismos adequados para a avaliação da largura de banda disponível. Assim, é importante para melhorar o desempenho do controlo de congestionamento em redes sem fios, incluir componentes que são adequados para esse tipo de ambientes. Um esquema de controlo de congestionamento que permita uma partilha eficiente e justa da capacidade da rede e da largura de banda disponível entre múltiplas aplicações concorrentes é crucial para a definição de novos, eficientes e justos mecanismos de controlo congestionamento para as redes sem fios. A Tese está dividida em três partes. Primeiro, apresentamos um estudo sobre a avaliação de desempenho de vários protocolos de controlo de congestionamento relativamente ao TCP, em redes sem fios em malha e ad-hoc. Os resultados obtidos mostram que os protocolos baseados na taxa de transmissão precisam de uma técnica de avaliação da largura de banda disponível que seja eficiente e precisa . A segunda parte da Tese apresenta um novo mecanismo de avaliação da capacidade da ligação e da largura de banda disponível, designada por rt-Winf (real time wireless inference). A avaliação é realizada em tempo real e sem a necessidade de inserir tráfego na rede. Os resultados obtidos através de simulação e emulação mostram que o rt-Winf obtém com precisão a largura de banda disponível e a capacidade da ligação sem sobrecarregar a rede. A terceira parte da Tese propõe novos mecanismos de controlo de congestionamento em redes sem fios. Estes mecanismos de controlo de congestionamento apresentam um conjunto de caracter ísticas novas para melhorar o seu desempenho, de entre as quais se destaca a utilização da informação de largura de banda disponível obtida pelo rt-Winf. Os resultados da avaliação destes mecanismos, utilizando o simulador ns-2, permitem concluir que a cooperação entre o rt-Winf e os algoritmos de controlo de congestionamento aumenta significativamente o desempenho da rede

ESTIMATION OF MAXIMUM ACHIEVABLE END-TO-END THROUGHPUT IN IEEE 802.11 BASED WIRELESS MESH NETWORKS

Wireless mesh networks can be quickly deployed in various situations to provide temporary to permanent wireless network coverage. To assess the feasibility and reliability of a given end-to-end communication need, it is essential for communication end points to accurately estimate their achievable end-to-end throughput. Several capacity, end-to-end throughput, and available bandwidth estimation techniques have been studied in the past for wired and wireless networks. The contention among wireless nodes arising due to the IEEE 802.11 medium access control protocol\u27s channel access mechanism renders the estimation of such network attributes challenging in multi-hop networks. This thesis evaluates Adhoc Probe, one state-of-the-art capacity estimation approach for ad hoc wireless networks and shows that it in fact measures achievable throughput instead of capacity and its estimated achievable throughput is not realizable. An analysis of end-to-end delays of the injected probe packets is presented to show the effects of medium access contention and network queuing on the delays and estimated achievable throughput subject to different network traffic patterns and multi-hop collisions. Based on the observations, an alternative less intrusive delay distribution based achievable throughput estimation solution is proposed. With ns-2 simulations, the scheme was shown to accurately estimate the achievable throughput under various topologies and cross traffic conditions

Estimation of the parameters of token-buckets in multi-hop environments

Bandwidth verification in shaping scenarios receives much attention of both operators and clients because of its impact on Quality of Service (QoS). As a result, measuring shapers’ parameters, namely the Committed Information Rate (CIR), Peak Information Rate (PIR) and Maximum Burst Size (MBS), is a relevant issue when it comes to assess QoS. In this paper, we present a novel algorithm, TBCheck, which serves to accurately measure such parameters with minimal intrusiveness. These measurements are the cornerstone for the validation of Service Level Agreements (SLA) with multiple shaping elements along an end-to-end path. As a further outcome of this measurement method, we define a formal taxonomy of multi-hop shaping scenarios. A thorough performance evaluation covering the latter taxonomy shows the advantages of TBCheck compared to other tools in the state of the art, yielding more accurate results even in the presence of cross-traffic. Additionally, our findings show that MBS estimation is unfeasible when the link load is high, regardless the measurement technique, because the token-bucket will always be empty. Consequently, we propose an estimation policy which maximizes the accuracy by measuring CIR during busy hours and PIR and MBS during off-peak hoursThis work was partially supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund under the project Tráfica (MINECO/FEDER TEC2015-69417-C2-1-R

The Measurement Manager: Modular and Efficient End-to-End Measurement Services

End-to-end network measurement is used to improve the precision, efficiency, and fairness for a variety of Internet protocols and applications. Measurement is typically performed in one of three ways: (1) actively, by injecting specially crafted probe packets into the network, (2) passively, by observing existing data traffic, and (3) customized, where applications use their own traffic to perform customized measurements. All current approaches suffer from drawbacks. Passive techniques are efficient but are constrained by the shape of the existing traffic. Active techniques are faster, more accurate and more flexible but impose a significantly higher overhead. And finally, custom techniques combine flexibility with efficiency, but are so tightly coupled with each application that they are not reusable. To address these shortcomings, we present the Measurement Manager, a practical, modular, and efficient service for performing end-to-end network measurements between hosts. Our architecture introduces a new hybrid approach to network measurement, where applications can pool together their data packets to be reused as padding inside network probes in a transparent and systematic way. We achieve this through the Measurement Manager Protocol (MGRP), a new transport protocol for sending probes that combines data packets and probes on the fly. In MGRP, active measurement algorithms specify the probes they wish to send using a Probe API and applications allow MGRP to use data from their own packets to fill the otherwise wasted probe padding. We have implemented the Measurement Manager inside the Linux kernel and have adapted existing applications and active measurement tools to use our system. Through experimentation we provide detailed empirical evidence that piggybacking data packets on measurement probes is not only feasible but improves source and cross traffic as well as the performance of measurement algorithms while not affecting their accuracy. We show that the Measurement Manager is an architecture with broad applications that can be used to build a generic measurement overlay network as well as expanding the solution space for estimation algorithms, since every application packet can now act as a potential probe

Rate Control State-of-the-art Survey

The majority of Internet traffic use Transmission Control Protocol (TCP) as the transport level protocol. It provides a reliable ordered byte stream for the applications. However, applications such as live video streaming place an emphasis on timeliness over reliability. Also a smooth sending rate can be desirable over sharp changes in the sending rate. For these applications TCP is not necessarily suitable. Rate control attempts to address the demands of these applications. An important design feature in all rate control mechanisms is TCP friendliness. We should not negatively impact TCP performance since it is still the dominant protocol. Rate Control mechanisms are classified into two different mechanisms: window-based mechanisms and rate-based mechanisms. Window-based mechanisms increase their sending rate after a successful transfer of a window of packets similar to TCP. They typically decrease their sending rate sharply after a packet loss. Rate-based solutions control their sending rate in some other way. A large subset of rate-based solutions are called equation-based solutions. Equation-based solutions have a control equation which provides an allowed sending rate. Typically these rate-based solutions react slower to both packet losses and increases in available bandwidth making their sending rate smoother than that of window-based solutions. This report contains a survey of rate control mechanisms and a discussion of their relative strengths and weaknesses. A section is dedicated to a discussion on the enhancements in wireless environments. Another topic in the report is bandwidth estimation. Bandwidth estimation is divided into capacity estimation and available bandwidth estimation. We describe techniques that enable the calculation of a fair sending rate that can be used to create novel rate control mechanisms.Peer reviewe

Can User-Level Probing Detect and Diagnose Common Home-WLAN Pathologies?

Common WLAN pathologies include low signal-to-noise ratio, congestion, hidden terminals or interference from non-802.11 devices and phenomena. Prior work has focused on the detection and diagnosis of such problems using layer-2 information from 802.11 devices and special-purpose access points and monitors, which may not be generally available. Here, we investigate a userlevel approach: is it possible to detect and diagnose 802.11 pathologies with strictly user-level active probing, without any cooperation from, and without any visibility in, layer-2 devices? In this paper, we present preliminary but promising results indicating that such diagnostics are feasible

Overhead in Available Bandwidth Estimation Tools: Evaluation and Analysis

The current Available Bandwidth Estimation Tools (ABET's) to perform an estimation, using probes packets are inserted into the network. The utilization These packages, makes ABET's are intrusive and consumes part of which is measuring bandwidth to noise known as "Overhead Estimation Tools" (OET); it’s can produce negative effects on measurements performed by the ABET. This paper presents a complete and comparative analysis of behavior of Available Bandwidth (av_bw), of the ABET's most representative, as well as: Abing, Diettopp, Pathload, PathChirp, Traceband, IGI, PTR, Assolo and Wbest. The study with real Internet traffic, shows the percentage of test that is a factor packets affecting two main aspects of the estimation. The first, the accuracy, and increased indicating that EOT is directly proportional to the percentage of RE, reaching up to 70% in the tool evaluated with most of 30% of Cross-Traffic (CT). And second, the techniques used to send probes packets highly influences the Estimation Time (ET), where some tools that use slops spend up to 240s to converge when there is 60% CT in the network, ensuring that the estimate this technique av_bw highly congested channel, OET as much is used, resulting in inaccuracies in measurement

An Android application for crowdsourcing 3G user experience

This report is composed by a project splited in two parts, a practical part and a research one. The first part of the project was done in Valencia (Spain) under the supervision of the company NUBESIS. We developed an Android application that is the mobile application for a website developed by the same company. We describe the problems we had while developing the application and the way we solved them. We will explain the diferent processes that take place in the application and how these processes are integrated in the application's functionality, we also talk about the user's interaction with the diferent screens and their behavior. The second part of the project is planned as a research project to improve the connectivity problem that can appear in the firrst application. This part was done in Sydney (Australia) in cooperation with the University of New South Wales (UNSW) and under the supervision of professor Mahbub Hassan. In this part we discuss the design and implementation of Android based 3G/HSDPA network bandwidth measurement mobile application. This application acts as a mobile sensor in a crowd sourcing system. We use a network link bandwidth estimation technique called packet pair probing, which can easily be implemented on a mobile platform and we also justify why we have chose the specific methodology after reviewing the related literature. We also propose a measurement initiation process with theMeasurement Server which allows the packet pair probing technique to reect an accurate download bandwidth on the measurement. We have calibrated and netune the measurement tool so it can contribute optimally to the crowd sourcing system by addressing issues such as usability, data consumption and power consumption. We include geo tags in each measurement we take and discuss the implementation issues addressed in the project. Finally, we introduce an algorithm which measures the download bandwidth in a timely fashion. We study the behaviour of the measurements by changing parameters such as packet size and packet train length. The results obtained were evaluated by comparing them to a reliable commercial bandwidth estimation tool under the same environment. Given these results we conducted a number of hypothesis tests where we used the T-statistic as the test statistic under the null hypothesis.Martínez Raga, M. (2011). An Android application for crowdsourcing 3G user experience. http://hdl.handle.net/10251/11987.Archivo delegad