<p>The purpose of this study was to gain more knowledge about the deleterious effects of decreased muscle protein concentration on skeletal muscle function, by measuring the concentrations of myosin and actin in single pig muscle fibres. The pigs were earlier used in an experimental animal model to study the early stages of acute quadriplegic myopathy (AQM), a disease that is found in mechanically ventilated intensive care unit patients. Percutaneous biopsies were taken from these pigs and where now used in this study.</p><p>Even though the method used was accurately tested and theoretically working, certain problems arose. These problems were unexpected and caused problems to the study. The method used to measure the concentration of myosin and actin, an ELISA, gave no logical results. The reason could not be found and because of the time limit of this project no results from the AQM-pigs were gained. The efforts to make the method work is described and discussed.</p>

Active Queue Management (AQM) aims to achieve high link utilization, low queuing delay and low loss rate in routers. However, it is difficult to adapt AQM parameters to constantly provide desirable transient and steady-state performance under highly dynamic network scenarios. They need to be a trade-off made between queuing delay and utilization. The queue size would become unstable when round-trip time or link capacity increases, or would be unnecessarily large when round-trip time or link capacity decreases. Effective ways of adapting AQM parameters to obtain good performance have remained a critical unsolved problem during the last fifteen years. This thesis firstly investigates existing AQM algorithms and their performance. Based on a previously developed dynamic model of TCP behaviour and a linear feedback model of TCP/RED, Auto-Parameterization RED (AP-RED) is proposed which unveils the mechanism of adapting RED parameters according to measurable network conditions. Another algorithm of Statistical Tuning RED (ST-RED) is developed for systematically tuning four key RED parameters to control the local stability in response to the detected change in the variance of the queue size. Under variable network scenarios like round-trip time, link capacity and traffic load, no manual parameter configuration is needed. The proposed ST-RED can adjust corresponding parameters rapidly to maintain stable performance and keep queuing delay as low as possible. Thus the sensitivity of RED's performance to different network scenarios is removed. This Statistical Tuning algorithm can be applied to a PI controller for AQM and a Statistical Tuning PI (ST-PI) controller is also developed. The implementation of ST-RED and ST-PI is relatively straightforward. Simulation results demonstrate the feasibility of ST-RED and ST-PI and their capabilities to provide desirable transient and steady-state performance under extensively varying network conditions.

Les troubles de la stabilité demeurent fréquents chez la personne âgée, dont la chute, avec des conséquences néfastes sur l’autonomie. Trois essais randomisés ont été menés afin d’identifier les variables distinguant le sujet âgé autonome chuteur et d’analyser l’incidence d’un traitement ostéopathique. La 1ère étude concerne 33 sujets : 15 chuteurs (68,3 ± 2,7 ans) et 18 non-chuteurs (67,7 ± 2,5 ans). Trois paramètres stabilométriques et trois tests cliniques permettent de distinguer les deux populations (p < 0,05). Le traitement ostéopathique améliore les caractéristiques évaluées des sujets chuteurs (plus de différence significative). La 2ème étude concerne 40 sujets chuteurs lombalgiques : 20 recevant un traitement ostéopathique(69,5 ± 3,9 ans) et 20 ne le recevant pas (69,9 ± 3,4 ans). Cette étude permet d’identifier que la mobilité lombaire est restreinte chez le sujet âgé chuteur et que le traitement ostéopathique améliore l’amplitude de mouvement lombaire juste après le traitement ainsi qu’à sept jours (p ≤0,01). La 3ème étude concerne 34 sujets : 17 chuteurs (71,3 ± 3,5 ans) et 17 non-chuteurs (71,5 ± 4,2 ans). Quatre variables cinématiques permettent de distinguer les deux populations (p ≤ 0,04). Le coefficient de détermination R2 ainsi que le Gait Variability Index confirment cette distinction. Le traitement ostéopathique améliore les caractéristiques évaluées des sujets chuteurs (plus de différence significative). / Balance disorders, as the fall, remain frequently in the elderly, with adverse consequences on the autonomy. Three randomized trials have been conducted to identify the parameters distinguishing the “fallers autonomous elderly” and to analyze the impact of an osteopathic treatment. The 1st study concerns 33 elderly patients: 15 fallers (68,3 ± 2,7 years) and 18 no-fallers (67,7 ± 2,5years). Three stabilometric parameters and three clinical tests distinguish the two populations (p <0,05). Moreover, the osteopathic treatment improves the evaluated characteristics of fallers elderly (no significant difference). The 2nd study concerns 40 fallers and lombalgic elderly: 20 receiving an osteopathic treatment (69,5 ±3,9 years) and 20 without the osteopathic treatment (69,9 ± 3,4 years). This study identifies that the lumbar mobility is restricted for every fallers elderly and the osteopathic treatment improves the lumbar motion just after the treatment, as well as seven days after it (p ≤ 0,01). The 3rd study concerns 34 elderly patients: 17 fallers (71,3 ± 3,5 years) and 17 no-fallers (71,5 ± 4,2years). Four cinematic parameters distinguish the two populations (p ≤ 0,04). The coefficient ofdetermination R2 and the Gait Variability Index confirm that distinction. The osteopathic treatment improves the evaluated characteristics of fallers elderly (no significant difference).

Internet applications have varied Quality of Service (QoS) Requirements. Traditional applications such as FTP and email are throughput sensitive since their quality is primarily affected by the throughput they receive. There are delay sensitive applications such as streaming audio/video and IP telephony, whose quality is more affected by the delay. The current Internet however does not provide QoS support to the applications and treats the packets from all applications as primarily throughput sensitive. Delay sensitive applications can however sacrifice throughput for delay to obtain better quality. We present a Traffic Sensitive QoS controller (TSQ) which can be used in conjunction with many existing Active Queue Management (AQM) techniques at the router. The applications inform the TSQ enabled router about their delay sensitivity by embedding a delay hint in the packet header. The delay hint is a measure of an application's delay sensitivity. The TSQ router on receiving packets provides a lower queueing delay to packets from delay sensitive applications based on the delay hint. It also increases the drop probability of such applications thus decreasing their throughput and preventing any unfair advantage over throughput sensitive applications. We have also presented the quality metrics of some typical Internet applications in terms of delay and throughput. The applications are free to choose their delay hints based on the quality they receive. We evaluated TSQ in conjunction with the PI-controller AQM over the Network Simulator (NS-2). We have presented our results showing the improvement in QoS of applications due to the presence of TSQ.

As ever more devices are connected to the internet, and applications turn ever more interactive, it becomes more important that the network can be counted on to respond reliably and without unnecessary delay. However, this is far from always the case today, as there can be many potential sources of unnecessary delay. In this thesis we focus on one of them: Excess queueing delay in network routers along the path, also known as bufferbloat. We focus on the home network, and treat the issue in three stages. We examine latency variation and queueing delay on the public internet and show that significant excess delay is often present. Then, we evaluate several modern AQM algorithms and packet schedulers in a residential setting, and show that modern AQMs can almost entirely eliminate bufferbloat and extra queueing latency for wired connections, but that they are not as effective for WiFi links. Finally, we go on to design and implement a solution for bufferbloat at the WiFi link, and also design a workable scheduler-based solution for realising airtime fairness in WiFi. Also included in this thesis is a description of Flent, a measurement tool used to perform most of the experiments in the other papers, and also used widely in the bufferbloat community. / HITS, 4707

Improving network performance in terms of efficiency, fairness in the bandwidth, and system stability has been a research issue for decades. Current Internet traffic control maintains sophistication in end TCPs but simplicity in routers. In each router, incoming packets queue up in a buffer for transmission until the buffer is full, and then the packets are dropped. This router queue management strategy is referred to as Drop Tail. End TCPs eventually detect packet losses and slow down their sending rates to ease congestion in the network. This way, the aggregate sending rate converges to the network capacity. In the past, Drop Tail has been adopted in most routers in the Internet due to its simplicity of implementation and practicability with light traffic loads. However Drop Tail, with heavy-loaded traffic, causes not only high loss rate and low network throughput, but also long packet delay and lengthy congestion conditions. To address these problems, active queue management (AQM) has been proposed with the idea of proactively and selectively dropping packets before an output buffer is full. The essence of AQM is to drop packets in such a way that the congestion avoidance strategy of TCP works most effectively. Significant efforts in developing AQM have been made since random early detection (RED), the first prominent AQM other than Drop Tail, was introduced in 1993. Although various AQMs also tend to improve fairness in bandwidth among flows, the vulnerability of short-lived flows persists due to the conservative nature of TCP. It has been revealed that short-lived flows take up traffic with a relatively small percentage of bytes but in a large number of flows. From the user’s point of view, there is an expectation of timely delivery of short-lived flows. Our approach is to apply artificial intelligence technologies, particularly fuzzy logic (FL), to address these two issues: an effective AQM scheme, and preferential treatment for short-lived flows. Inspired by the success of FL in the robust control of nonlinear complex systems, our hypothesis is that the Internet is one of the most complex systems and FL can be applied to it. First of all, state of the art AQM schemes outperform Drop Tail, but their performance is not consistent under different network scenarios. Research reveals that this inconsistency is due to the selection of congestion indicators. Most existing AQM schemes are reliant on queue length, input rate, and extreme events occurring in the routers, such as a full queue and an empty queue. This drawback might be overcome by introducing an indicator which takes account of not only input traffic but also queue occupancy for early congestion notification. The congestion indicator chosen in this research is traffic load factor. Traffic load factor is in fact dimensionless and thus independent of link capacity, and also it is easy to use in more complex networks where different traffic classes coexist. The traffic load indicator is a descriptive measure of the complex communication network, and is well suited for use in FL control theory. Based on the traffic load indicator, AQM using FL – or FLAQM – is explored and two FLAQM algorithms are proposed. Secondly, a mice and elephants (ME) strategy is proposed for addressing the problem of the vulnerability of short-lived flows. The idea behind ME is to treat short-lived flows preferably over bulk flows. ME’s operational location is chosen at user premise gateways, where surplus processing resources are available compared to other places. By giving absolute priority to short-lived flows, both short and long-lived flows can benefit. One problem with ME is starvation of elephants or long-lived flows. This issue is addressed by dynamically adjusting the threshold distinguishing between mice and elephants with the guarantee that minimum capacity is maintained for elephants. The method used to dynamically adjust the threshold is to apply FL. FLAQM is deployed to control the elephant queue with consideration of capacity usage of mice packets. In addition, flow states in a ME router are periodically updated to maintain the data storage. The application of the traffic load factor for early congestion notification and the ME strategy have been evaluated via extensive experimental simulations with a range of traffic load conditions. The results show that the proposed two FLAQM algorithms outperform some well-known AQM schemes in all the investigated network circumstances in terms of both user-centric measures and network-centric measures. The ME strategy, with the use of FLAQM to control long-lived flow queues, improves not only the performance of short-lived flows but also the overall performance of the network without disadvantaging long-lived flows.

Avec l'avènement d'Internet, le monde est entré dans une ère nouvelle. Celle d'un partage quasiment sans limite de l'information. Ce n'est pas seulement un medium de communication nouveau qui est apparu, mais bien aussi un changement dans la façon de vivre de chacun. L'un des aspects de cette révolution est le transport effectué par le réseau utilisant souvent le protocole TCP. Aujourd'hui encore les usages sont parfois limités par les débits disponibles. La nouvelle génération d'Internet, peut-être issue des recherches sur Internet 2, offrira des possibilités sans doute encore plus étonnantes. Ce mémoire porte sur l'étude du partage de bande passante par TCP. Elle commence par deux chapitre introductifs sur TCP (chapitre 1) et ses modèles mathématiques (chapitre 2) qui conduisent à trois parties. La première partie est très mathématique, partant d'un exemple très simple au chapitre 3 sur des tirages avec ou sans remise d'une urne, elle montre ensuite comment généraliser la méthode de champ moyen de «lookdown process» à des trajectoires avec des dynamiques complexes à travers trois chapitres ; le chapitre 4 pose le problème d'utilisateurs qui interagissent à travers une ressource partagée par l'intermédiaire de sauts poissonniens ; le chapitre 5 développe une méthode inspirée du «lookdown process» pour résoudre ce premier problème ; enfin, le chapitre 6 propose une généralisation où l'interaction se fait par des sauts à intensités mais aussi par des sauts synchrones. La deuxième partie présente un travail joint avec David McDonald et François Baccelli sur la modélisation de TCP dans le cas de téléchargements de longue durée et une généralisation pour tenir compte d'utilisateurs non persistants. Le chapitre 8 présente le modèle utilisé, il s'agit d'étudier un grand nombre d'utilisateurs qui partagent une ressource commune qui est la bande passante. Ces utilisateurs se servent du protocole TCP sous un certain nombre d'hypothèses simplificatrices (modèle fluide, nombre d'utilisateurs constant avec le temps). Le chapitre 9 poursuit en proposant la démonstration de la convergence en champ moyen : lorsque le nombre d'utilisateurs qui partagent une ressource rare devient grand, les équations des files d'attentes/débits au routeur deviennent des équations aux dérivées partielles déterministes. L'étude mathématique de ces équations de transport est l'objet du chapitre 10. Elles y sont établies, simplifiées et étudiées. En particulier, on y voit une étude de la stabilité d'une file d'attente sous certains contrôles centralisés comme RED. Cette partie s'achève avec le chapitre 11 qui propose une généralisation du modèle pour prendre en compte les utilisateurs du protocole HTTP sur TCP. La troisième partie est dédiée aux simulations. Le chapitre 12 montre certains aspects de la conception du simulateur des équations aux dérivées partielles des utilisateurs de TCP persistants et de leur généralisation à HTTP. Le simulateur est ensuite validé expérimentalement puis nous discutons des principales améliorations qu'il faudrait apporter au simulateur et au modèle. Enfin le chapitre 13 propose deux exemples d'utilisations du simulateur, le premier illustre le problème de la congestion pour les utilisateurs de HTTP en insistant sur le fait que le problème est plus grave qu'on pourrait s'y attendre ; le second présente un effet de turbulence mathématique pour HTTP/TCP, c'est à dire que dans certaines conditions, nous trouvons deux états limites, un où le débit est constant et un état oscillatoire où le débit moyen est moindre.

The purpose of this study was to gain more knowledge about the deleterious effects of decreased muscle protein concentration on skeletal muscle function, by measuring the concentrations of myosin and actin in single pig muscle fibres. The pigs were earlier used in an experimental animal model to study the early stages of acute quadriplegic myopathy (AQM), a disease that is found in mechanically ventilated intensive care unit patients. Percutaneous biopsies were taken from these pigs and where now used in this study. Even though the method used was accurately tested and theoretically working, certain problems arose. These problems were unexpected and caused problems to the study. The method used to measure the concentration of myosin and actin, an ELISA, gave no logical results. The reason could not be found and because of the time limit of this project no results from the AQM-pigs were gained. The efforts to make the method work is described and discussed.

Ce mémoire ne contient pas de résumé.

In the Internet of today there is a demand for both high bandwidth and low delays. Bandwidth-heavy applications such as large downloads or video streaming compete with more delay-sensitive applications; web-browsing, VoIP and video games. These applications represent a growing share of Internet traffic. Buffers are an essential part of network equipment. They prevent packet loss and help maintain hight throughput. As bandwidths have increased so have the buffer sizes. In some cases way to much. This, and the fact that Active Queue Management (AQM) is seldom implemented, has given rise to a phenomenon called Bufferbloat. Bufferbloat is manifested at the bottleneck of the network path by large flows creating standing queues that choke out smaller, and usually delay-sensitive, flows. Since the bottleneck is often located at the consumer edge, this is where the focus of this thesis lies. This work evaluates three different AQM solutions that lower delays without requiring complicated configuration; CoDel, FQ_CoDel and PIE. FQ_CoDel had the best performance in the tests, with the lowest consistent delays and high throughput. This thesis recommends that AQM is implemented at the network edge, preferably FQ_CoDel.