Design, implementation and evaluation of a QoS-aware transport protocol

In the context of a reconfigurable transport protocol framework, we propose a QoS-aware Transport Protocol (QSTP), specifically designed to operate over QoS-enabled networks with bandwidth guarantee. QSTP combines QoS-aware TFRC congestion control mechanism, which takes into account the network-level bandwidth reservations, with a Selective ACKnowledgment (SACK) mechanism in order to provide a QoS-aware transport service that fill the gap between QoS enabled network services and QoS constraint applications. We have developed a prototype of this protocol in the user-space and conducted a large range of measurements to evaluate this proposal under various network conditions. Our results show that QSTP allows applications to reach their negotiated QoS over bandwidth guaranteed networks, such as DiffServ/AF network, where TCP fails. This protocol appears to be the first reliable protocol especially designed for QoS network architectures with bandwidth guarantee

A Quality of Service Monitoring System for Service Level Agreement Verification

Service-level-agreement (SLA) monitoring measures network Quality-of-Service (QoS) parameters to evaluate whether the service performance complies with the SLAs. It is becoming increasingly important for both Internet service providers (ISPs) and their customers. However, the rapid expansion of the Internet makes SLA monitoring a challenging task. As an efficient method to reduce both complexity and overheads for QoS measurements, sampling techniques have been used in SLA monitoring systems. In this thesis, I conduct a comprehensive study of sampling methods for network QoS measurements. I develop an efficient sampling strategy, which makes the measurements less intrusive and more efficient, and I design a network performance monitoring software, which monitors such QoS parameters as packet delay, packet loss and jitter for SLA monitoring and verification. The thesis starts with a discussion on the characteristics of QoS metrics related to the design of the monitoring system and the challenges in monitoring these metrics. Major measurement methodologies for monitoring these metrics are introduced. Existing monitoring systems can be broadly classified into two categories: active and passive measurements. The advantages and disadvantages of both methodologies are discussed and an active measurement methodology is chosen to realise the monitoring system. Secondly, the thesis describes the most common sampling techniques, such as systematic sampling, Poisson sampling and stratified random sampling. Theoretical analysis is performed on the fundamental limits of sampling accuracy. Theoretical analysis is also conducted on the performance of the sampling techniques, which is validated using simulation with real traffic. Both theoretical analysis and simulation results show that the stratified random sampling with optimum allocation achieves the best performance, compared with the other sampling methods. However, stratified sampling with optimum allocation requires extra statistics from the parent traffic traces, which cannot be obtained in real applications. In order to overcome this shortcoming, a novel adaptive stratified sampling strategy is proposed, based on stratified sampling with optimum allocation. A least-mean-square (LMS) linear prediction algorithm is employed to predict the required statistics from the past observations. Simulation results show that the proposed adaptive stratified sampling method closely approaches the performance of the stratified sampling with optimum allocation. Finally, a detailed introduction to the SLA monitoring software design is presented. Measurement results are displayed which calibrate systematic error in the measurements. Measurements between various remote sites have demonstrated impressively good QoS provided by Australian ISPs for premium services

Minimally-intrusive frequent round trip time measurements using Synthetic Packet-Pairs

Accurate and frequent round trip time (RTT) measurements are important in testbeds and operational networks. Active measurement techniques inject probe packets that may modify the behaviour of the observed network and may produce misleading RTT estimates if the network handles probe packets differently to regular packets. Previous passive measurement techniques address these issues, but require precise time synchronisation or are limited to certain traffic types. We introduce Synthetic Packet-Pairs (SPP), a novel passive technique for RTT measurement. SPP provides frequently updated RTT measurements using any network traffic already present in the network without the need for time synchronisation. SPP accurately measures the RTT experienced by any application's traffic, even applications that do not exhibit symmetric client-server packet exchanges. We experimentally demonstrate the advantages of SPP

Specifying and Verifying Requirements for Transmission of Medical Data in Public Networks

The purpose of this study is to identify and verify the necessary Quality of Service metrics in public networks for an existing remote patient monitoring system called Mobile Viewers. Therefore, any abnormalities can be detected beforehand and the application quality can be seen from the end user's point of view. The name Mobile Viewers refer to three different client applications: Web Viewers, Pocket Viewers and Cellular Viewers. The literature part of this thesis reviews the former research studies dedicated to network performance measurements in 3G, 2.5G and Wireless LAN networks. Based on the review, the most suitable measurement methods, tools, metrics and environments are selected to be utilised during this study. In the first part of the thesis work, passive live measurement tests are executed within UMTS, GPRS, LAN and Wireless LAN networks in order to find out the delay, jitter and packet loss metrics for the individual Mobile Viewers. As a result, GPRS presents the highest delay, jitter and packet loss values leading to poor application quality. The second part of the thesis study focuses on identifying the quality requirements for Mobile Viewers. Initially, a network emulator tool is employed to emulate the necessary delay, jitter and packet loss metrics in order to test the application quality under different network conditions. Additional subjective user defined tests are executed to assess the quality for each viewer client. Finally, the limit delay, packet loss and jitter values, where the application quality starts to degrade, are presented. Additional future work may be carried out by observing the Mobile Viewers' performances with higher technologies for instance, HSDPA. Furthermore, the conclusions derived from the analysis of the measurements and the proposed requirements for Mobile Viewers should be validated by additional experiments with different client devices, measurement tools and longer measurement periods