11 research outputs found

    Label Space Reduction in MPLS Networks: How Much Can A Single Stacked Label Do?

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    Most network operators have considered reducing LSR label spaces (number of labels used) as a way of simplifying management of underlaying virtual private networks (VPNs) and therefore reducing operational expenditure (OPEX). The IETF outlined the label merging feature in MPLS-allowing the configuration of multipoint-to-point connections (MP2P)-as a means of reducing label space in LSRs. We found two main drawbacks in this label space reduction a)it should be separately applied to a set of LSPs with the same egress LSR-which decreases the options for better reductions, and b)LSRs close to the edge of the network experience a greater label space reduction than those close to the core. The later implies that MP2P connections reduce the number of labels asymmetricall

    NETWORKING 2009

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    Concepção e implementação de experiências laboratoriais sobre MPLS

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    Mestrado em Engenharia Electrónica e TelecomunicaçõesO Multiprotocol Label Switching (MPLS) é um mecanismo de transporte de dados, sob a forma de um protocolo agnóstico, com grande potencial de crescimento e adequação. Opera na “Camada 2.5” do modelo OSI e constitui um mecanismo de alto desempenho utilizado nas redes de núcleo para transportar dados de um nó da rede para outro. O sucesso do MPLS resulta do facto de permitir que a rede transporte todos os tipos de dados, desde tráfego IP a tráfego da camada de ligação de dados, devido ao encapsulamento dos pacotes dos diversos protocolos, permitindo a criação de “links virtuais” entre nós distantes. O MPLS pertence à família das “redes de comutação de pacotes”, sendo os pacotes de dados associados a “etiquetas” que determinam o seu encaminhamento, sem necessidade de examinar o conteúdo dos próprios pacotes. Isto permite a criação de circuitos “extremo-aextremo” através de qualquer tipo de rede de transporte e independentemente do protocolo de encaminhamento que é utilizado. O projecto do MPLS considera múltiplas tecnologias no sentido de prestar um serviço único de transporte de dados, tentando simultaneamente proporcionar capacidades de engenharia de tráfego e controlo “out-of-band”, uma característica muito atraente para uma implementação em grande escala. No fundo, o MPLS é uma forma de consolidar muitas redes IP dentro de uma única rede. Dada a importância desta tecnologia, é urgente desenvolver ferramentas que permitam entender melhor a sua complexidade. O MPLS corre normalmente nas redes de núcleo dos ISPs. No sentido de tornar o seu estudo viável, recorreu-se nesta dissertação à emulação para implementar cenários de complexidade adequada. Existem actualmente boas ferramentas disponíveis que permitem a recriação em laboratório de cenários bastante complicados. Contudo, a exigência computacional da emulação é proporcional à complexidade do projecto em questão, tornando-se rapidamente impossível de realizar numa única máquina. A computação distribuída ou a “Cloud Computing” são actualmente as abordagens mais adequadas e inovadoras apara a resolução deste problema. Esta dissertação tem como objectivo criar algumas experiências em laboratório que evidenciam aspectos relevantes da tecnologia MPLS, usando para esse efeito um emulador computacional, o Dynamips, impulsionado por generosas fontes computacionais disponibilizadas pela Amazon ec2. A utilização destas ferramentas de emulação permite testar cenários de rede e serviços reais em ambiente controlado, efectuando o debugging das suas configurações e optimizando o seu desempenho, antes de os colocar em funcionamento nas redes em operação.The Multiprotocol Label Switching (MPLS) is a highly scalable and agnostic protocol to carry network data. Operating at "Layer 2.5" of the OSI model, MPLS is an highperformance mechanism that is used at the network backbone for conveying data from one network node to the next. The success of MPLS results from the fact that it enables the network to carry all kinds of traffic, ranging from IP to layer 2 traffic, since it encapsulates the packets of the diverse network protocols, allowing the creation of "virtual links" between distant nodes. MPLS belongs to the family of packet switched networks, where labels are assigned to data packets that are forwarded based on decisions that rely only on the label contents, without the need to examine the packets contents. This allows the creation of end-to-end circuits across any type of transport medium, using any protocol. The MPLS design takes multiform transport technologies into account to provide a unified data-carrying service, attempting simultaneously to preserve traffic engineering and out-of-band control, a very attractive characteristic for large-scale deployment. MPLS is the way to consolidate many IP networks into a single one. Due to this obvious potential, it is urgent to develop means and tools to better understand its functioning and complexity. MPLS normally runs at the backbone of Service Providers networks, being deployed across an extensive set of expensive equipment. In order to turn the study of MPLS feasible, emulation was considered as the best solution. Currently, there are very good available tools to recreate, in a lab environment, quite complicated scenarios. However, the computational demand of the emulation is proportional to the complexity of the project, becoming quickly unfeasible in a single machine. Fortunately, distributed computing or Cloud computing are suitable and novel approaches to solve this computation problem. So, this work aims to create some lab experiments that can illustrate/demonstrate relevant aspects of the MPLS technology, using the Dynamips emulator driven by the computational resources that were made available by the Amazon ec2 cloud computing facilities. The utilization of these emulation tools allows testing real networks and service scenarios in a controlled environment, being able to debug their configurations and optimize their performance before deploying them in real operating networks

    Intelligent Network Infrastructures: New Functional Perspectives on Leveraging Future Internet Services

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    The Internet experience of the 21st century is by far very different from that of the early '80s. The Internet has adapted itself to become what it really is today, a very successful business platform of global scale. As every highly successful technology, the Internet has suffered from a natural process of ossification. Over the last 30 years, the technical solutions adopted to leverage emerging applications can be divided in two categories. First, the addition of new functionalities either patching existing protocols or adding new upper layers. Second, accommodating traffic grow with higher bandwidth links. Unfortunately, this approach is not suitable to provide the proper ground for a wide gamma of new applications. To be deployed, these future Internet applications require from the network layer advanced capabilities that the TCP/IP stack and its derived protocols can not provide by design in a robust, scalable fashion. NGNs (Next Generation Networks) on top of intelligent telecommunication infrastructures are being envisioned to support future Internet Services. This thesis contributes with three proposals to achieve this ambitious goal. The first proposal presents a preliminary architecture to allow NGNs to seamlessly request advanced services from layer 1 transport networks, such as QoS guaranteed point-to-multipoint circuits. This architecture is based on virtualization techniques applied to layer 1 networks, and hides from NGNs all complexities of interdomain provisioning. Moreover, the economic aspects involved were also considered, making the architecture attractive to carriers. The second contribution regards a framework to develop DiffServ-MPLS capable networks based exclusively on open source software and commodity PCs. The developed DiffServ-MPLS flexible software router was designed to allow NGN prototyping, that make use of pseudo virtual circuits and assured QoS as a starting point of development. The third proposal presents a state of the art routing and wavelength assignment algorithm for photonic networks. This algorithm considers physical layer impairments to 100% guarantee the requested QoS profile, even in case of single network failures. A number of novel techniques were applied to offer lower blocking probability when compared with recent proposed algorithms, without impacting on setup delay time

    Next generation control of transport networks

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    It is widely understood by telecom operators and industry analysts that bandwidth demand is increasing dramatically, year on year, with typical growth figures of 50% for Internet-based traffic [5]. This trend means that the consumers will have both a wide variety of devices attaching to their networks and a range of high bandwidth service requirements. The corresponding impact is the effect on the traffic engineered network (often referred to as the “transport network”) to ensure that the current rate of growth of network traffic is supported and meets predicted future demands. As traffic demands increase and newer services continuously arise, novel network elements are needed to provide more flexibility, scalability, resilience, and adaptability to today’s transport network. The transport network provides transparent traffic engineered communication of user, application, and device traffic between attached clients (software and hardware) and establishing and maintaining point-to-point or point-to-multipoint connections. The research documented in this thesis was based on three initial research questions posed while performing research at British Telecom research labs and investigating control of transport networks of future transport networks: 1. How can we meet Internet bandwidth growth yet minimise network costs? 2. Which enabling network technologies might be leveraged to control network layers and functions cooperatively, instead of separated network layer and technology control? 3. Is it possible to utilise both centralised and distributed control mechanisms for automation and traffic optimisation? This thesis aims to provide the classification, motivation, invention, and evolution of a next generation control framework for transport networks, and special consideration of delivering broadcast video traffic to UK subscribers. The document outlines pertinent telecoms technology and current art, how requirements I gathered, and research I conducted, and by which the transport control framework functional components are identified and selected, and by which method the architecture was implemented and applied to key research projects requiring next generation control capabilities, both at British Telecom and the wider research community. Finally, in the closing chapters, the thesis outlines the next steps for ongoing research and development of the transport network framework and key areas for further study

    Advanced techniques for multicast service provision in core transport networks

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    Although the network-based multicast service is the optimal way to support of a large variety of popular applications such as high-definition television (HDTV), videoon- demand (VoD), virtual private LAN service (VPLS), grid computing, optical storage area networks (O-SAN), video conferencing, e-learning, massive multiplayer online role-playing games (MMORPG), networked virtual reality, etc., there are a number of technological and operational reasons that prevents a wider deployment. This PhD work addresses this problem in the context of core transport network, by proposing and analyzing new cost-effective and scalable techniques to support multicast both at the Optical layer and at the Network layer (MPLS-IP networks). In the Optical layer, in particular in Wavelength Division Multiplexing (WDM) Optical Circuit Switched networks, current multicast-capable OXC node designs are of a great complexity and have high attenuation levels, mainly because of the required signal splitting operation plus the traversal of a complex switching stage. This makes multi-point support rarely included in commercial OXC nodes. Inspired in previous works in the literature, we propose a novel architecture that combines the best of splitting and tap-and-continue (TaC), called 2-STC (2-split-tap-and-continue) in the framework of integrated optics. A 2-STC OXC node is a flexible design capable of tapping and splitting over up to two outgoing links in order to obtain lower end-to-end latency than in TaC and an improved power budget distribution over split-and-delivery (SaD) designs. Another advantage of this architecture is its simplicity and the reduced number of components required, scaling well even for implementations of the node with many input/output ports. Extensive simulations show that the binary split (2-split) is quite enough for most real-life core network topologies scenarios, since the average node degree is usually between 3 and 4. A variant of this design, called 2-STCg, for making the node capable of optical traffic grooming (i.e. accommodation of low-speed demands into wavelength-links) is also presented. At the Network layer, one of the main reasons that hinder multicast deployment is the high amount of forwarding state information required in core routers, especially when a large number of medium/small-sized multicast demands arrive to the core network, because the state data that needs to be kept at intermediate core routers grows proportionally to the number of multicast demands. In this scenario, we study the aggregation of multicast demands into shared distribution trees, providing a set of techniques to observe the trade-off between bandwidth and state information. This study is made in the context of MPLS VPN-based networks, with the aggregation of multicast VPNs in different real network scenarios and using novel heuristics for aggregation. Still, the main problem of aggregation is the high percentage of wasted bandwidth that depends mainly on the amount of shared trees used. On the other hand, recent works have brought back Bloom filters as an alternative for multicast forwarding. In this approach the packet header contains a Bloom filter that is evaluated at each hop for matching with the corresponding outgoing link ID. Although this approach is claimed to be stateless, it presents serious drawbacks due to false positives, namely important forwarding anomalies (duplicated flows, packet storms and loops) and the header overhead. In order to solve these drawbacks we propose D-MPSS (Depth-Wise Multi-Protocol Stateless Switching). This technique makes use of a stack of Bloom filters instead of a single one for all the path/tree, each one including only the links of a given depth of the tree. Analytical studies and simulations show that our approach reduces the forwarding anomalies present in similar state-of-the-art techniques, achieving in most network scenarios a forwarding efficiency (useful traffic) greater than 95%. Finally, we study the possibility of using tree aggregation and Bloom filters together, and propose a set of techniques grouped as H-ABF techniques (hybrid aggregation - Bloom filter-based forwarding), which improve D-MPSS and other previously proposed techniques, practically eliminating the forwarding loops and increasing the forwarding efficiency up to more than 99% in most network scenarios. -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Aunque el servicio de multidifusión (multicast) basado en redes es la mejor manera de dar soporte a una gran variedad de aplicaciones populares como la televisión de alta definición (HDTV), el video bajo demanda (VoD), el servicio de LAN privadas virtuales (VPLS), la computación grid, las redes de área de almacenamiento óptico (O-SAN), la videoconferencia, la educación a distancia, los juegos masivos de rol en línea de múltiples jugadores (MMORPG), la realidad virtual en red, etc., hay varias razones tecnológicas y operacionales que le impiden un mayor despliegue. Esta tesis doctoral aborda este problema en el contexto de las redes troncales de transporte, proponiendo y analizando técnicas de bajo coste y escalables para dar soporte al multicast tanto para la capa óptica como para la capa de red (redes MPLS-IP). En la capa óptica, en particular en las redes ópticas conmutadas por circuitos con multiplexación de longitud de onda (WDM), los diseños de nodos OXC con capacidades multicast muestran una gran complejidad y altos niveles de atenuación, principalmente debido a la necesaria operación de división de la señal, además del paso de ella a través de una compleja fase de conmutación. Esto hace que el soporte multi-punto sea raramente incluido en los nodos OXC comerciales. Inspirados en trabajos previos de la literatura, proponemos una novedosa arquitectura que combina lo mejor de dividir (splitting) y tap-y-continuar (TaC), llamado 2-STC (2-split-tapand- continue) en el marco de trabajo de la óptica integrada. Un nodo OXC 2-STC es un diseño flexible capaz de hacer tapping (tomar una pequeña muestra de la señal) y dividir la señal hacia un máximo de dos enlaces de salida, con el fin de obtener una menor latencia terminal-a-terminal que en TaC y una mejorada distribución de la disponibilidad de potencia por encima de los diseños split-and-delivery (SaD). Otra ventaja de esta arquitectura es su simplicidad y el número reducido de componentes requerido, escalando bien para las implementaciones del nodo con muchos puertos de entrada/salida. Extensas simulaciones muestran que la división binaria (2-split) es prácticamente suficiente para la mayoría de las topologías de redes de transporte en la vida real, debido a que el grado promedio de los nodos es usualmente 3 y 4. Una variante de este diseño, llamada 2-STCg, para hacer el nodo capaz de realizar grooming (es decir, la capacidad de acomodar demandas de menor velocidad en longitudes de onda - enlaces) de tráfico óptico, es también presentada. En la capa de red, una de las principales razones que obstaculizan el despliegue del multicast es la gran cantidad de información del estado de reenvío requerida en los enrutadores de la red de transporte, especialmente cuando un gran número de demandas multicast de tamaño mediano/pequeño llegan a la red de transporte, ya que los datos de estado a ser almacenados en los enrutadores crecen proporcionalmente con el número de demandas multicast. En este escenario, estudiamos la agregación de demandas multicast en árboles de distribución, proporcionando un conjunto de técnicas para observar el equilibrio entre el ancho de banda y la información de estado. Este estudio está hecho en el contexto de las redes basadas en redes privadas virtuales (VPN) MPLS, con la agregación de VPNs multicast en distintos escenarios de redes reales y utilizando nuevos heurísticos para la agregación. Aún así, el principal problema de la agregación es el alto porcentaje de ancho de banda desperdiciado que depende principalmente de la cantidad de árboles compartidos usados. Por otro lado, trabajos recientes han vuelto a traer a los filtros de Bloom como una alternativa para realizar el reenvío multicast. En esta aproximación la cabecera del paquete contiene un filtro de Bloom que es evaluado en cada salto para emparejarlo con el identificador del enlace de salida correspondiente. Aunque se afirma que esta solución no utiliza información de estado, presenta serias desventajas debido a los falsos positivos, esto es, anomalías de reenvío importantes (flujos duplicados, tormentas de paquetes y bucles) y gasto de ancho de banda por la cabecera de los paquetes. Para poder resolver estos problemas proponemos D-MPSS (Depth- Wise Multi-Protocol Stateless Switching). Esta técnica hace uso de una pila de filtros de Bloom en lugar de uno sólo para todo el camino/árbol, incluyendo cada uno sólo los enlaces de una determinada profundidad del árbol. Estudios analíticos y simulaciones demuestran que nuestra propuesta reduce los anomalías de reenvío presentes en otras técnicas similares del estado del arte, alcanzando en la mayoría de escenarios reales una eficiencia de reenvío (tráfico útil) mayor que 95%. Finalmente, estudiamos la posibilidad de usar agregación de árboles y filtros de Bloom juntos, y proponemos un conjunto de técnicas agrupadas como técnicas HABF (hybrid aggregation - Bloom filter-based forwarding), que mejoran D-MPSS y las otras técnicas propuestas previamente, eliminando prácticamente los bucles e incrementando la eficiencia de reenvío hasta más de un 99% en la mayoría de los escenarios de redes

    Esquema de controlo para redes multicast baseadas com classes

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    Doutoramento em Engenharia ElectrotécnicaThe expectations of citizens from the Information Technologies (ITs) are increasing as the ITs have become integral part of our society, serving all kinds of activities whether professional, leisure, safety-critical applications or business. Hence, the limitations of the traditional network designs to provide innovative and enhanced services and applications motivated a consensus to integrate all services over packet switching infrastructures, using the Internet Protocol, so as to leverage flexible control and economical benefits in the Next Generation Networks (NGNs). However, the Internet is not capable of treating services differently while each service has its own requirements (e.g., Quality of Service - QoS). Therefore, the need for more evolved forms of communications has driven to radical changes of architectural and layering designs which demand appropriate solutions for service admission and network resources control. This Thesis addresses QoS and network control issues, aiming to improve overall control performance in current and future networks which classify services into classes. The Thesis is divided into three parts. In the first part, we propose two resource over-reservation algorithms, a Class-based bandwidth Over-Reservation (COR) and an Enhanced COR (ECOR). The over-reservation means reserving more bandwidth than a Class of Service (CoS) needs, so the QoS reservation signalling rate is reduced. COR and ECOR allow for dynamically defining over-reservation parameters for CoSs based on network interfaces resource conditions; they aim to reduce QoS signalling and related overhead without incurring CoS starvation or waste of bandwidth. ECOR differs from COR by allowing for optimizing control overhead minimization. Further, we propose a centralized control mechanism called Advanced Centralization Architecture (ACA), that uses a single state-full Control Decision Point (CDP) which maintains a good view of its underlying network topology and the related links resource statistics on real-time basis to control the overall network. It is very important to mention that, in this Thesis, we use multicast trees as the basis for session transport, not only for group communication purposes, but mainly to pin packets of a session mapped to a tree to follow the desired tree. Our simulation results prove a drastic reduction of QoS control signalling and the related overhead without QoS violation or waste of resources. Besides, we provide a generic-purpose analytical model to assess the impact of various parameters (e.g., link capacity, session dynamics, etc.) that generally challenge resource overprovisioning control. In the second part of this Thesis, we propose a decentralization control mechanism called Advanced Class-based resource OverpRovisioning (ACOR), that aims to achieve better scalability than the ACA approach. ACOR enables multiple CDPs, distributed at network edge, to cooperate and exchange appropriate control data (e.g., trees and bandwidth usage information) such that each CDP is able to maintain a good knowledge of the network topology and the related links resource statistics on real-time basis. From scalability perspective, ACOR cooperation is selective, meaning that control information is exchanged dynamically among only the CDPs which are concerned (correlated). Moreover, the synchronization is carried out through our proposed concept of Virtual Over-Provisioned Resource (VOPR), which is a share of over-reservations of each interface to each tree that uses the interface. Thus, each CDP can process several session requests over a tree without requiring synchronization between the correlated CDPs as long as the VOPR of the tree is not exhausted. Analytical and simulation results demonstrate that aggregate over-reservation control in decentralized scenarios keep low signalling without QoS violations or waste of resources. We also introduced a control signalling protocol called ACOR Protocol (ACOR-P) to support the centralization and decentralization designs in this Thesis. Further, we propose an Extended ACOR (E-ACOR) which aggregates the VOPR of all trees that originate at the same CDP, and more session requests can be processed without synchronization when compared with ACOR. In addition, E-ACOR introduces a mechanism to efficiently track network congestion information to prevent unnecessary synchronization during congestion time when VOPRs would exhaust upon every session request. The performance evaluation through analytical and simulation results proves the superiority of E-ACOR in minimizing overall control signalling overhead while keeping all advantages of ACOR, that is, without incurring QoS violations or waste of resources. The last part of this Thesis includes the Survivable ACOR (SACOR) proposal to support stable operations of the QoS and network control mechanisms in case of failures and recoveries (e.g., of links and nodes). The performance results show flexible survivability characterized by fast convergence time and differentiation of traffic re-routing under efficient resource utilization i.e. without wasting bandwidth. In summary, the QoS and architectural control mechanisms proposed in this Thesis provide efficient and scalable support for network control key sub-systems (e.g., QoS and resource control, traffic engineering, multicasting, etc.), and thus allow for optimizing network overall control performance.À medida que as Tecnologias de Informação (TIs) se tornaram parte integrante da nossa sociedade, a expectativa dos cidadãos relativamente ao uso desses serviços também demonstrou um aumento, seja no âmbito das atividades profissionais, de lazer, aplicações de segurança crítica ou negócios. Portanto, as limitações dos projetos de rede tradicionais quanto ao fornecimento de serviços inovadores e aplicações avançadas motivaram um consenso quanto à integração de todos os serviços e infra-estruturas de comutação de pacotes, utilizando o IP, de modo a extrair benefícios económicos e um controlo mais flexível nas Redes de Nova Geração (RNG). Entretanto, tendo em vista que a Internet não apresenta capacidade de diferenciação de serviços, e sabendo que cada serviço apresenta as suas necessidades próprias, como por exemplo, a Qualidade de Serviço - QoS, a necessidade de formas mais evoluídas de comunicação tem-se tornado cada vez mais visível, levando a mudanças radicais na arquitectura das redes, que exigem soluções adequadas para a admissão de serviços e controlo de recursos de rede. Sendo assim, este trabalho aborda questões de controlo de QoS e rede com o objetivo de melhorar o desempenho do controlo de recursos total em redes atuais e futuras, através da análise dos serviços de acordo com as suas classes de serviço. Esta Tese encontra-se dividida em três partes. Na primeira parte são propostos dois algoritmos de sobre-reserva, o Class-based bandwidth Over-Reservation (COR) e uma extensão melhorada do COR denominado de Enhanced COR (ECOR). A sobre-reserva significa a reserva de uma largura de banda maior para o serviço em questão do que uma classe de serviço (CoS) necessita e, portanto, a quantidade de sinalização para reserva de recursos é reduzida. COR e ECOR consideram uma definição dinâmica de sobre-reserva de parâmetros para CoSs com base nas condições da rede, com vista à redução da sobrecarga de sinalização em QoS sem que ocorra desperdício de largura de banda. O ECOR, por sua vez, difere do COR por permitir a otimização com minimização de controlo de overhead. Além disso, nesta Tese é proposto também um mecanismo de controlo centralizado chamado Advanced Centralization Architecture (ACA) , usando um único Ponto de Controlo de Decisão (CDP) que mantém uma visão ampla da topologia de rede e de análise dos recursos ocupados em tempo real como base de controlo para a rede global. Nesta Tese são utilizadas árvores multicast como base para o transporte de sessão, não só para fins de comunicação em grupo, mas principalmente para que os pacotes que pertençam a uma sessão que é mapeada numa determinada árvore sigam o seu caminho. Os resultados obtidos nas simulações dos mecanismos mostram uma redução significativa da sobrecarga da sinalização de controlo, sem a violação dos requisitos de QoS ou desperdício de recursos. Além disso, foi proposto um modelo analítico no sentido de avaliar o impacto provocado por diversos parâmetros (como por exemplo, a capacidade da ligação, a dinâmica das sessões, etc), no sobre-provisionamento dos recursos. Na segunda parte desta tese propôe-se um mecanismo para controlo descentralizado de recursos denominado de Advanced Class-based resource OverprRovisioning (ACOR), que permite obter uma melhor escalabilidade do que o obtido pelo ACA. O ACOR permite que os pontos de decisão e controlo da rede, os CDPs, sejam distribuídos na periferia da rede, cooperem entre si, através da troca de dados e controlo adequados (por exemplo, localização das árvores e informações sobre o uso da largura de banda), de tal forma que cada CDP seja capaz de manter um bom conhecimento da topologia da rede, bem como das suas ligações. Do ponto de vista de escalabilidade, a cooperação do ACOR é seletiva, o que significa que as informações de controlo são trocadas de forma dinâmica apenas entre os CDPs analisados. Além disso, a sincronização é feita através do conceito proposto de Recursos Virtuais Sobre-Provisionado (VOPR), que partilha as reservas de cada interface para cada árvore que usa a interface. Assim, cada CDP pode processar pedidos de sessão numa ou mais árvores, sem a necessidade de sincronização entre os CDPs correlacionados, enquanto o VOPR da árvore não estiver esgotado. Os resultados analíticos e de simulação demonstram que o controlo de sobre-reserva é agregado em cenários descentralizados, mantendo a sinalização de QoS baixa sem perda de largura de banda. Também é desenvolvido um protocolo de controlo de sinalização chamado ACOR Protocol (ACOR-P) para suportar as arquitecturas de centralização e descentralização deste trabalho. O ACOR Estendido (E-ACOR) agrega a VOPR de todas as árvores que se originam no mesmo CDP, e mais pedidos de sessão podem ser processados sem a necessidade de sincronização quando comparado com ACOR. Além disso, E-ACOR introduz um mecanismo para controlar as informações àcerca do congestionamento da rede, e impede a sincronização desnecessária durante o tempo de congestionamento quando os VOPRs esgotam consoante cada pedido de sessão. A avaliação de desempenho, através de resultados analíticos e de simulação, mostra a superioridade do E-ACOR em minimizar o controlo geral da carga da sinalização, mantendo todas as vantagens do ACOR, sem apresentar violações de QoS ou desperdício de recursos. A última parte desta Tese inclui a proposta para recuperação a falhas, o Survivability ACOR (SACOR), o qual permite ter QoS estável em caso de falhas de ligações e nós. Os resultados de desempenho analisados mostram uma capacidade flexível de sobrevivência caracterizada por um tempo de convergência rápido e diferenciação de tráfego com uma utilização eficiente dos recursos. Em resumo, os mecanismos de controlo de recursos propostos nesta Tese fornecem um suporte eficiente e escalável para controlo da rede, como também para os seus principais sub-sistemas (por exemplo, QoS, controlo de recursos, engenharia de tráfego, multicast, etc) e, assim, permitir a otimização do desempenho da rede a nível do controlo global

    Asymmetric tunnels in P2MP LSPs as a label space reduction method

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    The objective of traffic engineering is to optimize network resource utilization. Although several works have been published about minimizing network resource utilization, few works have focused on LSR (label switched router) label space. This paper proposes an algorithm that takes advantage of the MPLS label stack features in order to reduce the number of labels used in LSPs. Some tunnelling methods and their MPLS implementation drawbacks are also discussed. The described algorithm sets up NHLFE (next hop label forwarding entry) tables in each LSR, creating asymmetric tunnels when possible. Experimental results show that the described algorithm achieves a great reduction factor in the label space. The presented works apply for both types of connections: P2MP (point-to-multipoint) and P2P (point-to-point)

    Radio Communications

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    In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks
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