Quality of service support in differentiated services packet networks

During the past few years, new types of Internet applications which require performance beyond the best-effort service that is provided by the current Internet have emerged. These applications include the transmission of voice and video, which require a fixed end-to-end delay bound in order for the end-user to perceive an acceptable level of service quality. The Differentiated Services (Diffserv) model has been proposed recently to enhance the traditional best-effort service, and provide certain Quality of Serviee (QoS) guarantees to these applications. Its current definition, however, does not allow for a high level of flexibility or assurance and, therefore, it can not be widely deployed. In this paper, we introduce a new protocol for a Diffserv architecture which provides a simple and efficient solution to the above problem. It is a complete protocol, in the sense that it deals with the issues of packet scheduling, admission control, and congestion control. We will show, through experimental results, that our proposed protocol can improve the flexibility and assurance provided by current solutions, while maintaining a high level of network utilization.published_or_final_versio

Non-stationary service curves : model and estimation method with application to cellular sleep scheduling

In today’s computer networks, short-lived flows are predominant. Consequently, transient start-up effects such as the connection establishment in cellular networks have a significant impact on the performance. Although various solutions are derived in the fields of queuing theory, available bandwidths, and network calculus, the focus is, e.g., about the mean wake-up times, estimates of the available bandwidth, which consist either out of a single value or a stationary function and steady-state solutions for backlog and delay. Contrary, the analysis during transient phases presents fundamental challenges that have only been partially solved and is therefore understood to a much lesser extent. To better comprehend systems with transient characteristics and to explain their behavior, this thesis contributes a concept of non-stationary service curves that belong to the framework of stochastic network calculus. Thereby, we derive models of sleep scheduling including time-variant performance bounds for backlog and delay. We investigate the impact of arrival rates and different duration of wake-up times, where the metrics of interest are the transient overshoot and relaxation time. We compare a time-variant and a time-invariant description of the service with an exact solution. To avoid probabilistic and maybe unpredictable effects from random services, we first choose a deterministic description of the service and present results that illustrate that only the time-variant service curve can follow the progression of the exact solution. In contrast, the time-invariant service curve remains in the worst-case value. Since in real cellular networks, it is well known that the service and sleep scheduling procedure is random, we extend the theory to the stochastic case and derive a model with a non-stationary service curve based on regenerative processes. Further, the estimation of cellular network’s capacity/ available bandwidth from measurements is an important topic that attracts research, and several works exist that obtain an estimate from measurements. Assuming a system without any knowledge about its internals, we investigate existing measurement methods such as the prevalent rate scanning and the burst response method. We find fundamental limitations to estimate the service accurately in a time-variant way, which can be explained by the non-convexity of transient services and their super-additive network processes. In order to overcome these limitations, we derive a novel two-phase probing technique. In the first step, the shape of a minimal probe is identified, which we then use to obtain an accurate estimate of the unknown service. To demonstrate the minimal probing method’s applicability, we perform a comprehensive measurement campaign in cellular networks with sleep scheduling (2G, 3G, and 4G). Here, we observe significant transient backlogs and delay overshoots that persist for long relaxation times by sending constant-bit-rate traffic, which matches the findings from our theoretical model. Contrary, the minimal probing method shows another strength: sending the minimal probe eliminates the transient overshoots and relaxation times

Methods of Congestion Control for Adaptive Continuous Media

Since the first exchange of data between machines in different locations in early 1960s, computer networks have grown exponentially with millions of people now using the Internet. With this, there has also been a rapid increase in different kinds of services offered over the World Wide Web from simple e-mails to streaming video. It is generally accepted that the commonly used protocol suite TCP/IP alone is not adequate for a number of modern applications with high bandwidth and minimal delay requirements. Many technologies are emerging such as IPv6, Diffserv, Intserv etc, which aim to replace the onesize-fits-all approach of the current lPv4. There is a consensus that the networks will have to be capable of multi-service and will have to isolate different classes of traffic through bandwidth partitioning such that, for example, low priority best-effort traffic does not cause delay for high priority video traffic. However, this research identifies that even within a class there may be delays or losses due to congestion and the problem will require different solutions in different classes. The focus of this research is on the requirements of the adaptive continuous media class. These are traffic flows that require a good Quality of Service but are also able to adapt to the network conditions by accepting some degradation in quality. It is potentially the most flexible traffic class and therefore, one of the most useful types for an increasing number of applications. This thesis discusses the QoS requirements of adaptive continuous media and identifies an ideal feedback based control system that would be suitable for this class. A number of current methods of congestion control have been investigated and two methods that have been shown to be successful with data traffic have been evaluated to ascertain if they could be adapted for adaptive continuous media. A novel method of control based on percentile monitoring of the queue occupancy is then proposed and developed. Simulation results demonstrate that the percentile monitoring based method is more appropriate to this type of flow. The problem of congestion control at aggregating nodes of the network hierarchy, where thousands of adaptive flows may be aggregated to a single flow, is then considered. A unique method of pricing mean and variance is developed such that each individual flow is charged fairly for its contribution to the congestion

Application of learning algorithms to traffic management in integrated services networks.

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN027131 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Utilization-based delay guarantee techniques and their applications

Many real-time systems demand effective and efficient delay-guaranteed services to meet timing requirements of their applications. We note that a system provides a delay-guaranteed service if the system can ensure that each task will meet its predefined end-to-end deadline. Admission control plays a critical role in providing delayguaranteed services. The major function of admission control is to determine admissibility of a new task. A new task will be admitted into the system if the deadline of all existing tasks and the new task can be met. Admission control has to be efficient and efficient, meaning that a decision should be made quickly while admitting the maximum number of tasks. In this dissertation, we study a utilization-based admission control mechanism. Utilization-based admission control makes an admission decision based on a simple resource utilization test: A task will be admitted if the resource utilization is lower than a pre-derived safe resource utilization bound. The challenge of obtaining a safe resource utilization bound is how to perform delay analysis offline, which is the main focus of this dissertation. For this, we develop utilization-based delay guarantee techniques to render utilization-based admission control both efficient and effective, which is further confirmed with our data. We develop techniques for several systems that are of practical importance. We first consider wired networks with the Differentiated Services model, which is wellknown as its supporting scalable services in computer networks. We consider both cases of providing deterministic and statistical delay-guaranteed services in wired networks with the Differentiated Services model. We will then extend our work to wireless networks, which have become popular for both civilian and mission critical applications. The variable service capacity of a wireless link presents more of a challenge in providing delay-guaranteed services in wireless networks. Finally, we study ways to provide delayguaranteed services in component-based systems, which now serve as an important platform for developing a new generation of computer software. We show that with our utilization-based delay guarantee technique, component-based systems can provide efficient and effective delay-guaranteed services while maintaining such advantages as the reusability of components

Architectures for virtualization and performance evaluation in software defined networks

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