Design and implementation of multiple address parallel transmission architecture for storage area network

Master'sMASTER OF ENGINEERIN

Energy and power aware scheduling algorithm modeling for battery powered embedded systems

Energy management has always been recognized as a challenge in mobile systems, especially in modern OS-based mobile systems where multi-functioning are widely supported. Nowadays, it is common for a mobile system user to run multiple applications simultaneously while having a target battery lifetime in mind for a specific application. Traditional OS-level power management (PM) policies make their best effort to save energy under performance constraint, but fail to guarantee a target lifetime, leaving the painful trading off between the total performance of applications and the target lifetime to the user itself. This thesis provides a new way to deal with the problem. It is advocated that a strong energy-aware PM scheme should first guarantee a user-specified battery lifetime to a target application by restricting the average power of those less important applications, and in addition to that, maximize the total performance of applications without harming the lifetime guarantee. As a support, energy, instead of CPU or transmission bandwidth, should be globally managed as the first-class resource by the OS. As the first-stage work of a complete PM scheme, this thesis presents the energy-based fair queuing scheduling, a novel class of energy-aware scheduling algorithms which, in combination with a mechanism of battery discharge rate restricting, systematically manage energy as the first-class resource with the objective of guaranteeing a user-specified battery lifetime for a target application in OS-based mobile systems. Energy-based fair queuing is a cross-application of the traditional fair queuing in the energy management domain. It assigns a power share to each task, and manages energy by proportionally serving energy to tasks according to their assigned power shares. The proportional energy use establishes proportional share of the system power among tasks, which guarantees a minimum power for each task and thus, avoids energy starvation on any task. Energy-based fair queuing treats all tasks equally as one type and supports periodical time-sensitive tasks by allocating each of them a share of system power that is adequate to meet the highest energy demand in all periods. However, an overly conservative power share is usually required to guarantee the meeting of all time constraints. To provide more effective and flexible support for various types of time-sensitive tasks in general purpose operating systems, an extra real-time friendly mechanism is introduced to combine priority-based scheduling into the energy-based fair queuing. Since a method is available to control the maximum time one time-sensitive task can run with priority, the power control and time-constraint meeting can be flexibly traded off. A SystemC-based test-bench is designed to assess the algorithms. Simulation results show the success of the energy-based fair queuing in achieving proportional energy use, time-constraint meeting, and a proper trading off between them. La gestión de energía en los sistema móviles está considerada hoy en día como un reto fundamental, notándose, especialmente, en aquellos terminales que utilizando un sistema operativo implementan múltiples funciones. Es común en los sistemas móviles actuales ejecutar simultaneamente diferentes aplicaciones y tener, para una de ellas, un objetivo de tiempo de uso de la batería. Tradicionalmente, las políticas de gestión de consumo de potencia de los sistemas operativos hacen lo que está en sus manos para ahorrar energía y satisfacer sus requisitos de prestaciones, pero no son capaces de proporcionar un objetivo de tiempo de utilización del sistema, dejando al usuario la difícil tarea de buscar un compromiso entre prestaciones y tiempo de utilización del sistema. Esta tesis, como contribución, proporciona una nueva manera de afrontar el problema. En ella se establece que un esquema de gestión de consumo de energía debería, en primer lugar, garantizar, para una aplicación dada, un tiempo mínimo de utilización de la batería que estuviera especificado por el usuario, restringiendo la potencia media consumida por las aplicaciones que se puedan considerar menos importantes y, en segundo lugar, maximizar las prestaciones globales sin comprometer la garantía de utilización de la batería. Como soporte de lo anterior, la energía, en lugar del tiempo de CPU o el ancho de banda, debería gestionarse globalmente por el sistema operativo como recurso de primera clase. Como primera fase en el desarrollo completo de un esquema de gestión de consumo, esta tesis presenta un algoritmo de planificación de encolado equitativo (fair queueing) basado en el consumo de energía, es decir, una nueva clase de algoritmos de planificación que, en combinación con mecanismos que restrinjan la tasa de descarga de una batería, gestionen de forma sistemática la energía como recurso de primera clase, con el objetivo de garantizar, para una aplicación dada, un tiempo de uso de la batería, definido por el usuario, en sistemas móviles empotrados. El encolado equitativo de energía es una extensión al dominio de la energía del encolado equitativo tradicional. Esta clase de algoritmos asigna una reserva de potencia a cada tarea y gestiona la energía sirviéndola de manera proporcional a su reserva. Este uso proporcional de la energía garantiza que cada tarea reciba una porción de potencia y evita que haya tareas que se vean privadas de recibir energía por otras con un comportamiento más ambicioso. Esta clase de algoritmos trata a todas las tareas por igual y puede planificar tareas periódicas en tiempo real asignando a cada una de ellas una reserva de potencia que es adecuada para proporcionar la mayor de las cantidades de energía demandadas por período. Sin embargo, es posible demostrar que sólo se consigue cumplir con los requisitos impuestos por todos los plazos temporales con reservas de potencia extremadamente conservadoras. En esta tesis, para proporcionar un soporte más flexible y eficiente para diferentes tipos de tareas de tiempo real junto con el resto de tareas, se combina un mecanismo de planificación basado en prioridades con el encolado equitativo basado en energía. En esta clase de algoritmos, gracias al método introducido, que controla el tiempo que se ejecuta con prioridad una tarea de tiempo real, se puede establecer un compromiso entre el cumplimiento de los requisitos de tiempo real y el consumo de potencia. Para evaluar los algoritmos, se ha diseñado en SystemC un banco de pruebas. Los resultados muestran que el algoritmo de encolado equitativo basado en el consumo de energía consigue el balance entre el uso proporcional a la energía reservada y el cumplimiento de los requisitos de tiempo real

Packet scheduling strategies for emerging service models in the internet

Traditional as well as emerging new Internet applications such as video-conferencing and live multimedia broadcasts from Internet TV stations will rely on scheduling algorithms in switches and routers to meet a diversity of service requirements desired from the network. This dissertation focuses on four categories of service requirements that cover the vast majority of current as well as emerging new applications: best-effort service, guaranteed service (delay and bandwidth), controlled load service, and soft real-time service. For each of these service types, we develop novel packet scheduling strategies that achieve better performance and better fairness than existing strategies.Best-effort and guaranteed services: A fair packet scheduler designed for best- effort service can also be employed to achieve bandwidth and delay guarantees. This dissertation proposes a novel fair scheduling algorithm, called Greedy Fair Queueing (GrFQ),that explicitly incorporates the goal of achieving better fairness into the actions of the scheduler. A simplified version of the scheduler is also proposed for easier deployment in real networks. Controlled load service: This dissertation analyzes and defines requirements on packet schedulers serving traffic that request the controlled load service (part of the Integrated Services architecture). We then propose a novel scheduler, called the CL(®) scheduler, which provides service differentiation for aggregated traffic for controlled load service. The proposed scheduler satisfies the defined requirements with a very low processing complexity and without requiring per-flow management. Soft real-time service: We formally define the service requirements of soft real-time applications which have delay constraints but which can tolerate some packet losses. Two novel schedulers of different levels of complexity are proposed. These schedulers achieve better performance (lower overall loss rates) and better fairness than previously known schedulers.We adapt a metric used widely in economics, called the Gini index, to our purpose of evaluating the fairness achieved by our schedulers under real traffic conditions. The Gini index captures the instantaneous fairness achieved at most instants of time as opposed to previously used measures of fairness in the networking literature. Using real video, audio and gateway traffic traces, we show that the proposed schedulers achieve better performance and fairness characteristics than other known schedulers.Ph.D., Electrical Engineering -- Drexel University, 200

Mécanismes d'optimisation multi-niveaux pour IP sur satellites de nouvelle génération

L'objectif de cette thèse est de fournir aux réseaux satellitaires géostationnaires des outils d'amélioration de performances dans un contexte contraint, lié au support de communication qui présente une qualité variable. Les défis s'étendent de la couche d'accès au support (l'ordonnancement) à la couche transport (le comportement du TCP étant sensible au délai de propagation dans les réseaux géostationnaires). Nous faisons appel aux mécanismes cross-layer qui mettent en place des interactions entre entités protocolaires non adjacentes du modèle OSI offrant ainsi une adaptation immédiate au changement des conditions dans le réseau. Nous employons à ce but une technique cross-layer informant l'entité protocolaire TCP du débit disponible, permettant d'éviter des conséquences telles que la chute du débit et des pertes liées à la congestion des files d'attente. Nous mettons en oeuvre ce mécanisme au niveau d'un élément sensible du réseau géostationnaire, le proxy TCP. L'intérêt des techniques cross-layer a été mis en évidence au niveau de l'ordonnanceur présent au sein de la gateway d'un réseau DVB-S2/DVB-RCS. Ainsi, ils contribuent à la maximisation de la capacité du système, à l'assurance des contraintes de qualité de service, à l'équité de l'allocation de ressources, etc. Enfin, nous présentons une solution possible d'architecture cross-layer. Nous proposons des caractéristiques demandées pour une architecture cross-layer afin d'assurer l'évolutivité, la modularité et la co-existence avec l'architecture standard existante. ABSTRACT : The main objective of this thesis is to provide tools of improving performance of geostationary satellite networks, operating in a constrained environment mainly due to the variable quality of radio links. There are protocol layers being challenged by such characteristics, such as the medium access protocol and the transport layer protocol (TCP behaviour is impacted by the long propagation delay in geostationary satellite networks). We employ cross-layer mechanisms implementing interaction between non-adjacent protocol layers defined by the OSI architecture aiming at providing a rapid adaptation to changes in network state. We provide a cross-layer technique informing TCP protocol of the available network rate, thus preventing consequences such as TCP rate drop or loss due to buffer overflow. This mechanism is to be implemented in a sensible network element, such as a TCP proxy. Data link layer scheduler can benefit from the advantages of employing cross-layer mechanisms, especially at the gateway of a DVB-S2/DVB-RCS satellite network. The improved scheduler allows an efficient use of network resources and helps insuring quality of services constraints, resource allocation fairness, etc. Finally, we propose a cross-layer architecture along with in-demand characteristics able to offer an inter-operability with the existing architecture, an easy up-grade and design