The Uniformization Process of the Fast Congestion Notification (FN)

Fast Congestion Notification (FN) is one of the proactive queue management mechanisms that practices congestion avoidance to help avoid the beginning of congestion by marking or dropping packets before the routers queue gets full; and exercises congestion control, when congestion avoidance fails, by increasing the rate of packet marking or dropping. Technically, FN avoids the queue overflows by controlling the instantaneous queue size below the optimal queue size, and control congestion by keeping the average arrival rate close to the outgoing link capacity. Upon arrival of each packet, FN uses the instantaneous queue size and the average arrival rate to calculate the packet marking or dropping probability. FN marks or drops packets at fairly regular intervals to avoid long intermarking intervals and clustered packet marks or drops. Too many marked or dropped packets close together can cause global synchronization, and also too long packet intermarking times between marked or dropped packets can cause large queue sizes and congestion. This paper shows how FN controls the queue size, avoids congestion, and reduces global synchronization by uniformizing marked or dropped packet intervals.Comment: 5 Pages IEEE format, International Journal of Computer Science and Information Security, IJCSIS 2009, ISSN 1947 5500,Impact Factor 0.423, http://sites.google.com/site/ijcsis

Marginal productivity index policies for dynamic priority allocation in restless bandit models

Esta tesis estudia tres complejos problemas dinámicos y estocásticos de asignación de recursos: (i) Enrutamiento y control de admisión con información retrasada, (ii) Promoción dinámica de productos y el Problema de la mochila para artículos perecederos, y (iii) Control de congestión en “routers” con información del recorrido futuro. Debido a que la solución óptima de estos problemas no es asequible computacionalmente a gran y mediana escala, nos concentramos en cambio en diseñar políticas heurísticas de prioridad que sean computacionalmente tratables y cuyo rendimiento sea cuasi-óptimo. Modelizamos los problemas arriba mencionados como problemas de “multi-armed restless bandit” en el marco de procesos de decisión Markovianos con estructura especial. Empleamos y enriquecemos resultados existentes en la literatura, que constituyen un principio unificador para el diseño de políticas de índices de prioridad basadas en la relajación Lagrangiana y la descomposición de dichos problemas. Esta descomposición permite considerar subproblemas de optimización paramétrica, y en ciertos casos “indexables”, resolverlos de manera óptima mediante el índice de productividad marginal (MP). El índice MP es usado como medida de prioridad dinámica para definir reglas heurísticas de prioridad para los problemas originales intratables. Para cada uno de los problemas bajo consideración realizamos tal descomposición, identificamos las condiciones de indexabilidad, y obtenemos fórmulas para los índices MP o algoritmos computacionalmente tratables para su cálculo. Los índices MP correspondientes a cada uno de estos tres problemas pueden ser interpretados en términos de prioridades como el nivel de: (i) la penalización de dirigir un trabajo a una cola particular, (ii) la necesidad de promocionar un cierto artículo perecedero, y (iii) la utilidad de una transmisión de flujo particular. Además de la contribución práctica de la obtención de reglas heurísticas de prioridad para los tres problemas analizados, las principales contribuciones teóricas son las siguientes: (i) un algoritmo lineal en el tiempo para el cómputo de los índices MP en el problema de control de admisión con información retrasada, igualando, por lo tanto, la complejidad del mejor algoritmo existente para el caso sin retrasos, (ii) un nuevo tipo de política de índice de prioridad basada en la resolución de un problema (determinista) de la mochila, y (iii) una nueva extensión del modelo existente de “multi-armed restless bandit” a través de la incorporación de las llegadas aleatorias de los “restless bandits”.This dissertation addresses three complex stochastic and dynamic resource allocation problems: (i) Admission Control and Routing with Delayed Information, (ii) Dynamic Product Promotion and Knapsack Problem for Perishable Items, and (iii) Congestion Control in Routers with Future-Path Information. Since these problems are intractable for finding an optimal solution at middle and large scale, we instead focus on designing tractable and well-performing heuristic priority rules. We model the above problems as the multi-armed restless bandit problems in the framework of Markov decision processes with special structure. We employ and enrich existing results in the literature, which identified a unifying principle to design dynamic priority index policies based on the Lagrangian relaxation and decomposition of such problems. This decomposition allows one to consider parametric-optimization subproblems and, in certain “indexable” cases, to solve them optimally via the marginal productivity (MP) index. The MP index is then used as a dynamic priority measure to define heuristic priority rules for the original intractable problems. For each of the problems considered we perform such a decomposition, identify indexability conditions, and obtain formulae for the MP indices or tractable algorithms for their computation. The MP indices admit the following priority interpretations in the three respective problems: (i) undesirability for routing a job to a particular queue, (ii) promotion necessity of a particular perishable product, and (iii) usefulness of a particular flow transmission. Apart from the practical contribution of deriving the heuristic priority rules for the three intractable problems considered, our main theoretical contributions are the following: (i) a linear-time algorithm for computing MP indices in the admission control problem with delayed information, matching thus the complexity of the best existing algorithm under no delays, (ii) a new type of priority index policy based on solving a (deterministic) knapsack problem, and (iii) a new extension of the existing multi-armed restless bandit model by incorporating random arrivals of restless bandits

A VOICE PRIORITY QUEUE (VPQ) SCHEDULER FOR VOIP OVER WLANs

The Voice over Internet Protocol (VoIP) application has observed the fastest growth in the world of telecommunication. The Wireless Local Area Network (WLAN) is the most assuring of technologies among the wireless networks, which has facilitated high-rate voice services at low cost and good flexibility. In a voice conversation, each client works as a sender and as a receiver depending on the direction of traffic flow over the network. A VoIP application requires a higher throughput, less packet loss and a higher fairness index over the network. The packets of VoIP streaming may experience drops because of the competition among the different kinds of traffic flow over the network. A VoIP application is also sensitive to delay and requires the voice packets to arrive on time from the sender to the receiver side without any delay over WLANs. The scheduling system model for VoIP traffic is still an unresolved problem. A new traffic scheduler is necessary to offer higher throughput and a higher fairness index for a VoIP application. The objectives of this thesis are to propose a new scheduler and algorithms that support the VoIP application and to evaluate, validate and verify the newly proposed scheduler and algorithms with the existing scheduling algorithms over WLANs through simulation and experimental environment. We proposed a new Voice Priority Queue (VPQ) scheduling system model and algorithms to solve scheduling issues. VPQ system model is implemented in three stages. The first stage of the model is to ensure efficiency by producing a higher throughput and fairness for VoIP packets. The second stage will be designed for bursty Virtual-VoIP Flow (Virtual-VF) while the third stage is a Switch Movement (SM) technique. Furthermore, we compared the VPQ scheduler with other well known schedulers and algorithms. We observed in our simulation and experimental environment that the VPQ provides better results for the VoIP over WLANs

Telecommunications Networks

This book guides readers through the basics of rapidly emerging networks to more advanced concepts and future expectations of Telecommunications Networks. It identifies and examines the most pressing research issues in Telecommunications and it contains chapters written by leading researchers, academics and industry professionals. Telecommunications Networks - Current Status and Future Trends covers surveys of recent publications that investigate key areas of interest such as: IMS, eTOM, 3G/4G, optimization problems, modeling, simulation, quality of service, etc. This book, that is suitable for both PhD and master students, is organized into six sections: New Generation Networks, Quality of Services, Sensor Networks, Telecommunications, Traffic Engineering and Routing