<p>An important aspect of development and research in the field of computer networking systems is evaluation. Through evaluation, performance and behavior of software and protocols over a network can be determined. A network emulator is one of several tools available to accomplish this.</p><p>In this thesis, the network emulator Dummynet is described, as well as its extension KauNet. KauNet extends Dummynet by introducing pattern-driven emulation. A pattern defines specific points at which to apply a certain computer network characteristic or behavior. The use of patterns allow an increased control and repeatability of an emulation. Repeating a test with an identical configuration and the same pattern will yield identical results.</p><p>The goal of the project was to add a new functionality to KauNet. The new functionality consists of a notification system capable of passing information from KauNet to external observers. By adding this new functionality, emulation statistics can be available for the observers immediately when occurring. Another example of information that can be forwarded, is simulated cross-layer information. For KauNet to know when and what information to send, a new type of pattern has been created, called trigger pattern. Trigger patterns behave similarly to the existing patterns, sharing the same structure and processing in KauNet. Through the use of trigger patterns, events may be raised at specific points. The notification system may then be used to pass the event information.</p><p>This thesis describes the evaluation, design and implementation of the trigger patterns and notification system in KauNet. Finally, it concludes with a verification of the new trigger functionality in a usage example.</p><p> </p>

An important aspect of development and research in the field of computer networking systems is evaluation. Through evaluation, performance and behavior of software and protocols over a network can be determined. A network emulator is one of several tools available to accomplish this. In this thesis, the network emulator Dummynet is described, as well as its extension KauNet. KauNet extends Dummynet by introducing pattern-driven emulation. A pattern defines specific points at which to apply a certain computer network characteristic or behavior. The use of patterns allow an increased control and repeatability of an emulation. Repeating a test with an identical configuration and the same pattern will yield identical results. The goal of the project was to add a new functionality to KauNet. The new functionality consists of a notification system capable of passing information from KauNet to external observers. By adding this new functionality, emulation statistics can be available for the observers immediately when occurring. Another example of information that can be forwarded, is simulated cross-layer information. For KauNet to know when and what information to send, a new type of pattern has been created, called trigger pattern. Trigger patterns behave similarly to the existing patterns, sharing the same structure and processing in KauNet. Through the use of trigger patterns, events may be raised at specific points. The notification system may then be used to pass the event information. This thesis describes the evaluation, design and implementation of the trigger patterns and notification system in KauNet. Finally, it concludes with a verification of the new trigger functionality in a usage example.

Available Bandwidth Estimation Techniques and Tools (ABETTs) have recently been envisioned as a supporting mechanism in areas such as compliance of service level agreements, network management, traffic engineering and real-time resource provisioning, flow and congestion control, construction of overlay networks, fast detection of failures and network attacks, and admission control. However, it is unknown whether current ABETTs can run efficiently in any type of network, under different network conditions, and whether they can provide accurate available bandwidth estimates at the timescales needed by these applications. This dissertation investigates techniques and tools able to provide accurate, low overhead, reliable, and fast available bandwidth estimations. First, it shows how it is that the network can be sampled to get information about the available bandwidth. All current estimation tools use either the probe gap model or the probe rate model sampling techniques. Since the last technique introduces high additional traffic to the network, the probe gap model is the sampling method used in this work. Then, both an analytical and experimental approach are used to perform an extensive performance evaluation of current available bandwidth estimation tools over a flexible and controlled testbed. The results of the evaluation highlight accuracy, overhead, convergence time, and reliability performance issues of current tools that limit their use by some of the envisioned applications. Single estimations are affected by the bursty nature of the cross traffic and by errors generated by the network infrastructure. A hidden Markov model approach to end-to-end available bandwidth estimation and monitoring is investigated to address these issues. This approach builds a model that incorporates the dynamics of the available bandwidth. Every sample that generates an estimation is adjusted by the model. This adjustment makes it possible to obtain acceptable estimation accuracy with a small number of samples and in a short period of time. Finally, the new approach is implemented in a tool called Traceband. The tool, written in ANSI C, is evaluated and compared with Pathload and Spruce, the best estimation tools belonging to the probe rate model and the probe gap model, respectively. The evaluation is performed using Poisson, bursty, and self-similar synthetic cross traffic and real traffic from a network path at University of South Florida. Results show that Traceband provides more estimations per unit time with comparable accuracy to Pathload and Spruce and introduces minimum probing traffic. Traceband also includes an optional moving average technique that smooths out the estimations and improves its accuracy even further.

User perceived latency is the most prominent performance issue influencing the World Wide Web (www) presently. Hyper-Text Transfer Protocol(HTTP) and Transmission Control Protocol (TCP) have been the backbone of web transport for decades, thus received a lot of attention recently due to end-to-end performance degradation in mobile environments. Inefficiencies of HTTP and TCP strongly affect web response time mainly in resource limited devices. HTTP compression reduces some of the burden imposed by TCP slow start phase. However, compression is still an underutilized feature of the web today [1]. In order to fulfill the end user expectations, we can optimize HTTP to improve Page Load Time (PLT), low memory usage and better network utilization. SPDY, a web latency reducing protocol and HTTP pipelining are a recent proposal to provide faster information exchange over web. Through the course of this work, we present a comprehensive study of new approaches to reduce mobile web latency. At first, we measure the PLT after implementing SPDY, HTTP and HTTP pipelining. Secondly, we also analyze the performance of these protocols after tuning the network parameters like bandwidth and round-trip time (RTT). Finally, we compare the performance of HTTP and other latency reducing protocols. We have conducted all experiments over DummyNet under user-configured network conditions. We critically discuss the challenges of shifting from HTTP to these latency-reducing protocols.

L'Internet du futur aura a transporter les donnees de nouvelles applications avec des garanties de qualite de service (QdS). De ce besoin resulte la necessite d'en re-concevoir l'architecture. Par ailleurs, la structure de l'Internet, compose de domaines independants vis a vis de la gestion de la QdS, pose le probleme de la continuite du service lors de la traversee de plusieurs domaines. Face a ces deux problematiques, la these soutenue est celle d'un systeme de communication offrant des garanties de QdS par flux applicatif dans un environnement Internet multi domaines. Son architecture integre un plan communication comportant plusieurs services/protocoles aux niveaux Transport et IP, et un plan signalisation assurant la gestion des ressources a la frontiere des domaines. Nos contributions sont les suivantes. Nous proposons un modele de caracterisation des services IP et Transport, etaye par : (1) des mesures realisees sur une plate forme nationale, (2) une etude en simulation (ns-2) et (3) des mesures realisees sur une plate-forme emulant (Dummynet) un Internet multi domaines. Nous etendons l'architecture de communication proposee dans des travaux anterieurs de facon a abstraire le niveau applicatif de la complexite du choix des services Transport et IP, et a optimiser l'utilisation des ressources du reseau. Nous specifions en UML et implementons en Java notre proposition d'architecture de signalisation permettant d'assurer la continuite du service offert aux applications sur tous les domaines traverses. Enfin, nous testons le systeme de communication avec deux types d'applications multimedias sur une plate-forme emulant le comportement de plusieurs domaines DiffServ.