Bandwidth constraint models: a performance study

Paper presented at IEEE GLOBECOM 2006 - 2006 Global Telecommunications Conference. San Francisco, CA: pp. 4150664.Bandwidth constraint models have been a topic of intense discussions at the IETF meetings. Three conventional methods have been described in informational IETF RFCs and their performance on a single link has been analyzed and discussed in the literature. In this article, we take a further step into analyzing their performance and optimal bandwidth constraint setting for a real network scenario. A new model is proposed and compared to existing ones when failure events may cause preemption of traffic trunks in a network. Our simulations results provide great insight on the benefits of the methods

A Survey on Communication Networks for Electric System Automation

Published in Computer Networks 50 (2006) 877–897, an Elsevier journal. The definitive version of this publication is available from Science Direct. Digital Object Identifier:10.1016/j.comnet.2006.01.005In today’s competitive electric utility marketplace, reliable and real-time information become the key factor for reliable delivery of power to the end-users, profitability of the electric utility and customer satisfaction. The operational and commercial demands of electric utilities require a high-performance data communication network that supports both existing functionalities and future operational requirements. In this respect, since such a communication network constitutes the core of the electric system automation applications, the design of a cost-effective and reliable network architecture is crucial. In this paper, the opportunities and challenges of a hybrid network architecture are discussed for electric system automation. More specifically, Internet based Virtual Private Networks, power line communications, satellite communications and wireless communications (wireless sensor networks, WiMAX and wireless mesh networks) are described in detail. The motivation of this paper is to provide a better understanding of the hybrid network architecture that can provide heterogeneous electric system automation application requirements. In this regard, our aim is to present a structured framework for electric utilities who plan to utilize new communication technologies for automation and hence, to make the decision making process more effective and direct.This work was supported by NEETRAC under Project #04-157

Методи оптимізації мультисервісної мережі

Робота публікується згідно наказу Ректора НАУ від 27.05.2021 р. №311/од "Про розміщення кваліфікаційних робіт здобувачів вищої освіти в репозиторії університету". Керівник дипломної роботи: професор кафедри ТКРС, Плющь О.Г.В даний час телекомунікації знаходяться на етапі технологічної еволюції. Телекомунікації мають великі шанси для зростання в найближчому майбутньому. Пропонованих послуг стає більше, вони персоналізовані та вимагають відповідної класифікації за допомогою об’єктивних та репрезентативних параметрів, котрі дають можливість визначити обмеження, дотримуючись котрих, досягаються необхідні результати з точки зору QoS. Ключовою розробкою телекомунікаційних систем протягом останніх двох десятиліть стала еволюція від мережі з комутацією каналів до мережі з комутацією пакетів. Зараз багато операторів переносять свої PSTNs з мереж з комутацією каналів. Цей новий підхід часто називають мережею наступного покоління (NGN), що дозволяє мережевим операторам запускати всі послуги (голос, дані та відео) в одній мережі

Quality of service technologies for multimedia applications in next generation networks

Next Generation Networks are constantly evolving towards solutions that allow the operator to provide advanced multimedia applications with QoS guarantees in heterogeneous, multi-domain and multi-services networks. Other than the unquestionable advantages inherent the ability to simultaneously handle traffic flows at different QoS levels, these architectures require management systems to efficiently perform quality guarantees and network resource utilization. These issues have been addressed in this thesis. DiffServ-aware Traffic Engineering (DS-TE) has been considered as reference architecture for the deployment of the quality management systems. It represents the most advanced technology to accomplish either network scalability and service granularity goals. On the basis of DS-TE features, a methodology for traffic and network resource management has been defined. It provides some rules for QoS service characterization and allows to implement Traffic Engineering policies with a class-based approach. A set of basic parameters for quality evaluation has been defined, that are the Key Performance Indicators; some mathematical model to derive the statistical nature of traffic have been analyzed and an algorithm to improve the fulfillment of quality of service targets and to optimize network resource utilization. It is aimed at reducing the complexity inherent the setting of some of the key parameters in the NGN architectures. Multidomain scenarios with technologies different from DS-TE have been also evaluated, defining some methodologies for network interoperability. Simulations with Opnet Modeler confirmed the efficacy of the proposed system in computing network configurations with QoS targets. With regard to QoS performance at the application level, video streaming applications in wireless domains have been particularly addressed. A rate control algorithm to adjust the rate on a per-window basis has been defined, making use of a short-term prediction of the network delay to keep the probability of playback buffer starvation lower than a desired threshold during each window. Finally, a framework for mutual authentication in web applications has been proposed and evaluated. It integrates an IBA password technique with a challenge-response scheme based on a shared secret key for image scrambling. The wireless environment is mainly addressed by the proposed system, which tries to overcome the severe constraints on security, data transmission capability and user friendliness imposed by such environment

Preemption control of multi-class loss networks

This thesis addresses the analysis and optimization of preemption in multi-class loss networks. Preemption, admission control and rate adaptation, are control mechanisms that enable loss network operators to provide quality of service (QoS) guarantees for admitted calls. This research includes two parts: i) performance characterization of a two parallel link loss network servicing multiple classes of calls under a speci c preemption and admission policy, and ii) preemption and admission control policy analysis for a single loss link servicing two classes of calls.In Part I, we consider a two parallel link multi-class loss network, where a call may preempt, if necessary, any calls with lower priorities and may in turn be preempted by any calls with higher priorities. The preemption policy permits both preemption from a preferred link to a backup link if possible, and eviction from either link if necessary. Our contributions in this part include: i) characterizing the rates of each class causing preemption of active lower priority calls, and therates of each class being preempted by an arriving higher priority call in Erlang-B functions when all classes share a common service rate; ii) simple expressions of these preemption rates through uniform asymptotic approximation; and iii) asymptotic approximation of these preemption rates using nearly completely decomposable (NCD) Markov chain techniques when classes have individual service rates.After analyzing the performance of a typical policy, we would also like to study various policies. In Part II, we analyze di erent preemption and admission control policies for a two-class loss link where per-class revenue is earned per unit time for each active call, and an instantaneous preemption cost is incurred whenever the preemption mechanism is employed. Our contributions in this part include: i) showing that under reasonable reward models, if we always preempt when the link is full, then it is better not to preempt at non-full states; ii) a su cient condition under which the average revenue of optimal preemption policy without admission control exceeds that of optimal admission control policy without preemption, which are established via policy improvement theorems fromstochastic dynamic programming.Ph.D., Computer Engineering -- Drexel University, 201

Metodologie di ottimizzazione orientate alla QoS e applicate alle reti NGN, Multiservizio e multidominio

La presente tesi tratta lo studio di tecniche di ottimizzazione della rete con un approccio orientato sia al traffico che alle risorse di rete. Un’attenta analisi dello scenario e delle tipologie di traffico, ha consentito la definizione e la scelta dei parametri di qualità, i quali permettono di agire attivamente sull'efficienza della rete e sulla possibilità di implementare una politica di gestione della QoS. Inoltre, sono stati analizzati vari approcci architetturali relativi alla rete di trasporto che hanno condotto alla definizione di alcune linee guida utili, sin nella fase di progettazione, per predisporre al meglio la fruibilità di servizi diversificati e di alta qualità. La soluzione architetturale che meglio sposa gli obiettivi di performance è data dall’integrazione di MPLS e Diffserv con applicazione del Traffic Engineering (DS-TE), in cui, all’approccio di differenziazione del trattamento del traffico sulla base dell’appartenenza a classi di servizio (CoS), si affianca il meccanismo dell’MPLS, che offre garanzie di qualità end-to-end, per la costruzione dei percorsi, Label Switch Path (LSP), su cui inoltrare gli aggregati di traffico; infine, il TE permette una gestione efficiente delle risorse. Relativamente alla rete di backbone DS-TE, il focus è andato principalmente sulle problematiche di ottimizzazione del routing degli LSP. In particolare, si definiscono delle metodologie che consentono un miglior bilanciamento del carico sulla rete, ma soprattutto, che permettono agli aggregati classificati con una maggiore priorità di essere sempre serviti. Oltre all’approccio di riottimizzazione globale degli LSP sulla rete, è stata proposta una procedura che, ad ogni richiesta di un nuovo LSP, individua un percorso ottimo di instradamento,ricorrendo, ove necessario, ad una tecnica di preemption ottimizzata per rimuove LSP a priorità inferiore, e nel contempo, cerca per questi un percorso alternativo, riducendo il service disruption. Per quanto riguarda l’ottimizzazione della rete a garanzia della qualità per alcune tipologie di servizio specifiche, è stato preso in esame il caso delle applicazioni video-streaming che riscuotono, oggigiorno, grande interesse. In particolare, lo scenario considerato è quello di una rete di tipo wireless che, per la sua natura, produce un throughput di tipo bursty e, quindi, rende molto difficile l’alta qualità dello streaming video. L’algoritmo proposto è di tipo window-based e prevede un Source Rate Control che modifica il rate di sorgente compensando i periodi altalenanti tra basso ed alto throughput in modo tale da evitare il tipico “saw” effect. Il rate viene modificato periodicamente all’inizio di ogni finestra temporale, il suo valore si ottiene imponendo che il valore della probabilità di starvation, del buffer nell’end-system sia inferiore ad una certa soglia per tutta la durata della finestra. Tale scopo è perseguito facendo una previsione a breve-termine del ritardo che il traffico subirà nella rete per la durata della finestra, a partire dalle informazioni raccolte nelle finestre precedenti

Priority realloc : a threefold mechanism for route and resources allocation in EONs

Backbone networks are responsible for long-haul data transport serving many clients with a large volume of data. Since long-haul data transport service must rely on a robust high capacity network the current technology broadly adopted by the industry is Wavelength Division Multiplexing (WDM). WDM networks enable one single fiber to operate with multiple high capacity channels, drastically increasing the fiber capacity. In WDM networks each channel is associated with an individual wavelength. Therefore a whole wavelength capacity is assigned to a connection, causing waste of bandwidth in case the connection bandwidth requirement is less than the channel total capacity. In the last half decade, Elastic Optical Networks (EON) have been proposed and developed based on the flexible use of the optical spectrum known as the flexigrid. EONs are adaptable to clients requirements and may enhance optical networks performance. For these reasons, research community and data transport providers have been demonstrating increasingly high interest in EONs which are likely to replace WDM as the universally adopted technology in backbone networks in the near future. EONs have two characteristics that may limit its efficient resources use. The spectrum fragmentation, inherent to the dynamic EON operation, decreases the network capacity to assign resources to connection requests increasing network blocking probability. The spectrum fragmentation also intensifies the denial of service to higher rate request inducing service unfairness. Due to the fact EONs were just recently developed and proposed, the aforementioned issues were not yet extensively studied and solutions are still being proposed. Furthermore, EONs do not yet provide specific features as differentiated service mechanisms. Differentiated service strategies are important in backbone networks to guarantee client's diverse requirements in case of a network failure or the natural congestion and resources contention that may occur at some periods of time in a network. Impelled by the foregoing facts, this thesis objective is three-fold. By means of developing and proposing a mechanism for routing and resources assignment in EONs, we intend to provide differentiated service while decreasing fragmentation level and increasing service fairness. The mechanism proposed and explained in this thesis was tested in an EON simulation environment and performance results indicated that it promotes beneficial performance enhancements when compared to benchmark algorithms.Redes backbone sao responsáveis pelo transporte de dados à longa distância que atendem a uma grande quantidade de clientes com um grande volume de dados. Como redes backbone devem basear-se em uma rede robusta e de alta capacidade, a tecnologia atual amplamente adotada pela indústria é Wavelength Division Multiplexing (WDM). Redes WDM permitem que uma única fibra opere com múltiplos canais de alta largura de banda, aumentando drasticamente a capacidade da fibra. Em redes WDM cada canal está associado a um comprimento de onda particular. Por conseguinte, toda capacidade do comprimento de onda é atribuída a uma única conexão, fazendo com que parte da largura de banda seja desperdiçada no caso em que a requisição de largura de banda da conexão seja menor do que a capacidade total do canal. A partir da metade da última década, as Redes Ópticas Elásticas (Elastic Optical Networks - EON) têm sido propostas e desenvolvidas com base no uso flexível do espectro óptico conhecido como flexigrid. EONs são adaptáveis às requisiçes por banda dos clientes e podem, portanto, melhorar o desempenho das redes ópticas. Por estas razões, EONs têm recebido cada vez mais interesse dos meios de pesquisa e provedores de serviço e provavelmente substituirão WDM como a tecnologia universalmente adotada pela indústria em redes backbone. EONs têm duas características que podem limitar a utilização eficiente de recursos. A fragmentação do espectro, inerente à operação dinâmica das EONs, pode diminuir a capacidade da rede em distribuir recursos ao atender às solicitações por conexões aumentando a probabilidade de bloqueio na rede. A fragmentação do espectro também intensifica a negação de serviço às solicitações por taxa de transmissão mais elevada, gerando injustiça no serviço prestado. Como EONs foram desenvolvidas recentemente, respostas às questões acima mencionadas ainda estão sob estudo e soluções continuam sendo propostas na literatura. Além disso, EONs ainda não fornecem funções específicas como um mecanismo que proveja diferenciação de serviço. Estratégias de diferenciação de serviço são importantes em redes backbone para garantir os diversos requisitos dos clientes em caso de uma falha na rede ou do congestionamento e disputa por recursos que podem ocorrer em alguns períodos em uma rede. Impulsionada pelos fatos anteriormente mencionados, esta tese possui três objetivos. Através do desenvolvimento e proposta de um mecanismo de roteamento e atribuição de recursos para EONs, temos a intenção de disponibilizar diferenciação de serviço, diminuir o nível de fragmentação de espectro e aumentar a justiça na distribuição de serviços. O mecanismo proposto nesta tese foi testado em simulações de EONs. Resultados indicaram que o mecanismo proposto promove benefícios através do aprimoramento da performance de uma rede EON quando comparado com algoritmos de referência.Les xarxes troncals son responsables per el transport de dades a llarga distància que serveixen a una gran quantitat de clients amb un gran volum de dades. Com les xarxes troncals han d'estar basades en una xarxa robusta i d'alta capacitat, la tecnologia actual àmpliament adoptada per la indústria és el Wavelength Division Multiplexing (WDM). Xarxes WDM permeten operar amb una sola fibra multicanal d'alt ample de banda, el que augmenta molt la capacitat de la fibra. A les xarxes WDM cada canal est a associat amb una longitud d'ona particular. En conseqüència, tota la capacitat del canal es assignada a una sola connexió, fent que part dels recurs siguin perduts en el cas en que l'ample de banda sol licitada sigui menys que la capacitat total del canal. A gairebé deu anys les xarxes òptiques elàstiques (Elastic Optical Networks -EON) son propostes i desenvolupades basades en el ús visible de l'espectre òptic conegut com Flexigrid. EONs són adaptables a les sol·licituds per ample de banda dels clients i per tant poden millorar el rendiment de les xarxes òptiques. Per aquestes raons, EONs han rebut cada vegada més interès en els mitjans d’investigació i de serveis i, probablement, han de reemplaçar el WDM com la tecnologia universalment adoptada en les xarxes troncals. EONs tenen dues característiques que poden limitar l'ús eficient dels recursos seus. La fragmentació de l'espectre inherent al funcionament dinàmic de les EONs, pot disminuir la capacitat de la xarxa en distribuir els recursos augmentant la probabilitat de bloqueig de connexions. La fragmentació de l'espectre també intensifica la denegació de les sol·licituds de servei per connexions amb una major ample de banda, el que genera injustícia en el servei ofert. Com les EONs s'han desenvolupat recentment, solucions als problemes anteriors encara estan en estudi i les solucions segueixen sent proposades en la literatura. D'altra banda, les EONs encara no proporcionen funcions especifiques com mecanisme de diferenciació de provisió de serveis. Estratègies de diferenciació de servei són importants en les xarxes troncals per garantir les diverses necessitats dels clients en cas d'una fallada de la xarxa o de la congestió i la competència pels recursos que es poden produir en alguns períodes. Impulsada pels fets abans esmentats, aquesta tesi te tres objectius. A través del desenvolupament i proposta d'un mecanisme d'enrutament i assignació de recursos per EONs, tenim la intenció d'oferir la diferenciació de serveis, disminuir el nivell de fragmentació de l'espectre i augmentar l'equitat en la distribució dels serveis. El mecanisme proposat en aquesta tesi ha estat provat en simulacions EONs. Els resultats van indicar que el mecanisme promou millores en el rendiment de la EON, en comparació amb els algoritmes de referència

An adaptive framework for end-to-end quality of service management

Ph.DDOCTOR OF PHILOSOPH