15 research outputs found

    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

    A Survey on the Path Computation Element (PCE) Architecture

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    Quality of Service-enabled applications and services rely on Traffic Engineering-based (TE) Label Switched Paths (LSP) established in core networks and controlled by the GMPLS control plane. Path computation process is crucial to achieve the desired TE objective. Its actual effectiveness depends on a number of factors. Mechanisms utilized to update topology and TE information, as well as the latency between path computation and resource reservation, which is typically distributed, may affect path computation efficiency. Moreover, TE visibility is limited in many network scenarios, such as multi-layer, multi-domain and multi-carrier networks, and it may negatively impact resource utilization. The Internet Engineering Task Force (IETF) has promoted the Path Computation Element (PCE) architecture, proposing a dedicated network entity devoted to path computation process. The PCE represents a flexible instrument to overcome visibility and distributed provisioning inefficiencies. Communications between path computation clients (PCC) and PCEs, realized through the PCE Protocol (PCEP), also enable inter-PCE communications offering an attractive way to perform TE-based path computation among cooperating PCEs in multi-layer/domain scenarios, while preserving scalability and confidentiality. This survey presents the state-of-the-art on the PCE architecture for GMPLS-controlled networks carried out by research and standardization community. In this work, packet (i.e., MPLS-TE and MPLS-TP) and wavelength/spectrum (i.e., WSON and SSON) switching capabilities are the considered technological platforms, in which the PCE is shown to achieve a number of evident benefits

    Journal of Telecommunications and Information Technology, 2009, nr 1

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    kwartalni

    Pour un mécanisme de protection différenciée unique contre la gestion ainsi que les pannes : DiffServ*

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    L'avĂšnement de l'Internet multiservice met fin Ă  l'Ăšre du rĂ©seautage de nature meilleur effort. Cette nouvelle caractĂ©ristique est trĂšs souhaitable et prometteuse sur plusieurs plans mais elle reste sujette Ă  la capacitĂ© du rĂ©seau de protĂ©ger chaque catĂ©gorie de trafic selon sa prioritĂ© et ses exigences en qualitĂ© de service. Quand le rĂ©seau est dĂ©ployĂ© sur une infrastructure optique, une des prĂ©occupations des plus importantes est sa capacitĂ© de survie et le maintien d'un service adĂ©quat Ă  toutes les applications suite Ă  une panne physique. Nous savons qu'une simple coupure de fibre provoque des pertes Ă©normes en capacitĂ© de transmission et si laissĂ©e sans surveillance, elle peut causer des dĂ©gradations majeures dans la qualitĂ© de service perçue par les usagers du rĂ©seau. Bien qu'il existe dĂ©jĂ  des mĂ©canismes de protection physique qui sont conçus spĂ©cifiquement pour remĂ©dier Ă  de telles situations, ces options sont gĂ©nĂ©ralement trĂšs coĂ»teuses et difficilement adaptable aux besoins variĂ©s de chaque classe de trafic d'un rĂ©seau multiserviceNous proposons alors un modĂšle innovateur de protection diffĂ©renciĂ©e du trafic, DiffServ*, qui permet de rĂ©pondre aux exigences particuliĂšres en qualitĂ© de service et de protection de chacune des classes de trafic et qui introduit une robustesse accrue et des Ă©conomies importantes en matiĂšre d'utilisation de ressources d'un rĂ©seau IP/WDM. DiffServ* se distingue par l'utilisation combinĂ©e de l'architecture des services diffĂ©renciĂ©es Ă  la couche logique d'un rĂ©seau et de la technique d'agrĂ©gation de liens ou canaux disjoints Ă  sa couche physiqueNotre modĂšle de protection diffĂ©renciĂ©e du trafic en cas de pannes a Ă©tĂ© soumis Ă  l'Ă©preuve, nous avons utilisĂ© la simulation pour Ă©tudier sa performance et nous l'avons comparĂ© Ă  un modĂšle de protection physique homologue, DiffProtect. Les rĂ©sultats montrent que DiffServ* permet en moyenne de garantir une meilleure protection que DiffProtect en cas de pannes simples et multiples. DiffProtect n'est plus performant que dans certaines situations de pannes et de trafic trĂšs particuliĂšres. Une Ă©valuation subsĂ©quente de la fiabilitĂ© d'un rĂ©seau qui utilise DiffServ*, une Ă©tude de coĂ»t de son dĂ©ploiement et une Ă©tude de cas qui cible les rĂ©seaux MPLS-DiffServ TE confirment davantage la supĂ©rioritĂ© de DiffServ* par rapport Ă  tout autre option de protection diffĂ©renciĂ©e envisageableNous rappelons que DiffServ* se base sur les techniques de diffĂ©renciation de service de la couche logique pour protĂ©ger le trafic en cas de pannes de composantes optiques. Ceci est inĂ©dit puisque ces mĂȘmes techniques sont originalement conçues que pour protĂ©ger le trafic en cas de congestion dans la couche logique. Alors pour dĂ©montrer dĂ©finitivement que DiffServ* est rĂ©alisable et fonctionnel nous rĂ©alisons une expĂ©rience de dĂ©ploiement pratique de DiffServ* en laboratoire Ă  l'aide d'Ă©quipements de communication rĂ©el. MalgrĂ© les divergences techniques entre la modĂ©lisation thĂ©orique de DiffServ* et de son implĂ©mentation, DiffServ* est dĂ©montrĂ© performant, fiable, Ă©conomique et rĂ©alisable en pratiqueNous clĂŽturons ce projet par une planification de dĂ©ploiement ; cette derniĂšre permet de gĂ©nĂ©raliser le dĂ©ploiement de DiffServ* Ă  toute topologie IP/WDM et d'en dimensionner la couche logique. Notre procĂ©dure approche les situations qui requiĂšrent la fiabilitĂ© spĂ©cifique de DiffProtect en offrant un modĂšle d'optimisation complet sur le dĂ©ploiement de la protection MixProtect multicouche qui utilise DiffServ* et DiffProtect dans le mĂȘme rĂ©sea

    Distributed control architecture for multiservice networks

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    The research focuses in devising decentralised and distributed control system architecture for the management of internetworking systems to provide improved service delivery and network control. The theoretical basis, results of simulation and implementation in a real-network are presented. It is demonstrated that better performance, utilisation and fairness can be achieved for network customers as well as network/service operators with a value based control system. A decentralised control system framework for analysing networked and shared resources is developed and demonstrated. This fits in with the fundamental principles of the Internet. It is demonstrated that distributed, multiple control loops can be run on shared resources and achieve proportional fairness in their allocation, without a central control. Some of the specific characteristic behaviours of the service and network layers are identified. The network and service layers are isolated such that each layer can evolve independently to fulfil their functions better. A common architecture pattern is devised to serve the different layers independently. The decision processes require no co-ordination between peers and hence improves scalability of the solution. The proposed architecture can readily fit into a clearinghouse mechanism for integration with business logic. This architecture can provide improved QoS and better revenue from both reservation-less and reservation-based networks. The limits on resource usage for different types of flows are analysed. A method that can sense and modify user utilities and support dynamic price offers is devised. An optimal control system (within the given conditions), automated provisioning, a packet scheduler to enforce the control and a measurement system etc are developed. The model can be extended to enhance the autonomicity of the computer communication networks in both client-server and P2P networks and can be introduced on the Internet in an incremental fashion. The ideas presented in the model built with the model-view-controller and electronic enterprise architecture frameworks are now independently developed elsewhere into common service delivery platforms for converged networks. Four US/EU patents were granted based on the work carried out for this thesis, for the cross-layer architecture, multi-layer scheme, measurement system and scheduler. Four conference papers were published and presented

    Efficient Passive Clustering and Gateways selection MANETs

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    Passive clustering does not employ control packets to collect topological information in ad hoc networks. In our proposal, we avoid making frequent changes in cluster architecture due to repeated election and re-election of cluster heads and gateways. Our primary objective has been to make Passive Clustering more practical by employing optimal number of gateways and reduce the number of rebroadcast packets

    Reliability and Quality of Service in Opportunistic Spectrum Access

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    RÉSUMÉ Les rĂ©seaux radio-cognitif constituent une des meilleures options technologiques pour les rĂ©seaux sans-fil futurs. Afin d’étudier comment la fiabilitĂ© devrait ĂȘtre redĂ©finie dans ces rĂ©seaux, nous Ă©tudions d'abord les sources les plus frĂ©quentes de panne dans les rĂ©seaux sans-fil et fournissons une procĂ©dure systĂ©matique de classement des pannes. Il est ensuite expliquĂ© comment les radios cognitives peuvent profiter de leur propre capacitĂ© Ă  mettre en Ɠuvre des mĂ©canismes efficaces de prĂ©vention et de rĂ©cupĂ©ration contre les pannes et ainsi assurer des communications sans-fil fiables et de qualitĂ© de service constante. En considĂ©rant des normes arrivantes sur la base de l'OSA, ce qui distingue un rĂ©seau radio-cognitif de ses prĂ©dĂ©cesseurs est des changements frĂ©quents de canal ainsi que de nouvelles exigences telles la dĂ©tection de disponibilitĂ© et la dĂ©cision d'utilisation du spectre. Nous nous concentrons sur cet aspect et modĂ©lisons la remise du spectre comme une panne. Par consĂ©quent, amĂ©liorer la fiabilitĂ© est Ă©quivalent Ă  augmenter le temps moyen entre pannes, Ă  rendre plus efficace le processus de rĂ©cupĂ©ration et Ă  rĂ©duire le temps moyen de rĂ©paration. Nous Ă©tudions donc d'abord l'impact du temps de rĂ©cupĂ©ration sur la performance du rĂ©seau radio-cognitif. En classifiant les pannes en dures et souples, il est examinĂ© comment la disponibilitĂ©, le temps moyen entre pannes et le temps moyen jusqu'Ă  la rĂ©paration sont touchĂ©s par le procĂšs de rĂ©cupĂ©ration. Nous observons que le temps dĂ©pensĂ© pour la rĂ©cupĂ©ration empĂȘche le rĂ©seau d'atteindre le maximum de disponibilitĂ©. Par consĂ©quent, pour obtenir un temps plus Ă©levĂ© entre pannes et un temps de rĂ©paration plus court, une option disponible est d'augmenter le nombre de canaux pouvant ĂȘtre utilisĂ©s par le rĂ©seau radio-cognitif, de sorte que, avec une haute probabilitĂ©, un utilisateur qui a ratĂ© le canal puisse trouver bientĂŽt un nouveau canal. De l'autre cĂŽtĂ©, un mĂ©canisme de rĂ©cupĂ©ration efficace est nĂ©cessaire pour mieux profiter de ce grand nombre de canaux; l'amĂ©lioration de la rĂ©cupĂ©ration est donc indispensable. Pour Ă©tudier l'impact de la rĂ©cupĂ©ration sur les couches plus hautes (e.g., la couche liaison et rĂ©seau), l’approche de l’analyse de file d'attente est choisie. Compte tenu des pĂ©riodes de rĂ©cupĂ©ration comme une interruption de service, un modĂšle gĂ©nĂ©ral de file d'attente de M/G/1 avec des interruptions est proposĂ©. DiffĂ©rents paramĂštres de fiabilitĂ© et de qualitĂ© de service peuvent ĂȘtre trouvĂ©s Ă  partir de ce modĂšle de file d'attente pour Ă©tudier comment la spĂ©cification des canaux, tels la distribution des pĂ©riodes de disponibilitĂ© et d'indisponibilitĂ©, et la spĂ©cification de l'algorithme de rĂ©cupĂ©ration, tels la durĂ©e de rĂ©cupĂ©ration, affectent les paramĂštres de performance comme la perte de paquets, de retard et de gigue, et aussi le temps entre pannes. Pour soutenir la diffĂ©renciation des classes de trafic, nous proposons une approche de file d'attente avec prioritĂ©. Nous proposons une extension des rĂ©sultats du modĂšle de file d'attente gĂ©nĂ©rale et prĂ©sentons quatre diffĂ©rentes disciplines de file d'attente de prioritĂ©, allant d'un rĂ©gime prĂ©emptif absolu Ă  un rĂ©gime complĂštement non prĂ©emptif. Les nouvelles disciplines augmentent la flexibilitĂ© et la rĂ©solution de dĂ©cision et permettent au noeud CR de contrĂŽler l'interaction des diffĂ©rentes classes de trafic avec plus de prĂ©cision.---------- ABSTRACT Cognitive-radio based wireless networks are a technology of choice for incoming wireless networks. To investigate how reliability should be redefined for these networks, we study the most common sources of failure in wireless networks and provide a systematic failure classification procedure. It is then explained how cognitive radios can use their inherent capabilities to implement efficient prevention and recovery mechanisms to combat failures and thereby provide more reliable communications and consistent quality of service in wireless networks. Considering incoming OSA-based standards, what distinguishes a cognitive radio network from its predecessors is the frequent spectrum handovers along with new requirements such as spectrum sensing and spectrum usage decision. We thus focus on this aspect and model the spectrum handover as a failure, so improving the reliability is equivalent to increasing the mean time to failure, improving the recovery process and shortening the mean time to repair. We first study the impact of the recovery time on the performance of the cognitive radio network. By classifying the failures into hard and soft, it is investigated how the availability, mean time to failure and mean time to repair are affected by the recovery time. It is observed that the time spent for recovery prevents the network from reaching the maximum availability. Therefore, to achieve a high mean time to hard failure and low mean time to repair, an available option is to increase the number of channels, so that with a high probability, a user who missed the channel can soon find a new channel. On the other side, an efficient recovery scheme is required to better take advantage of a large number of channels. Recovery improvement is thus indispensable. To study the impact of recovery on higher communication layers, a queueing approach is chosen. Considering the recovery periods as a service interruption, a general M/G/1 queueing model with interruption is proposed. Different reliability and quality of service parameters can be found from this queueing model to investigate how channel parameters, such as availability and unavailability periods, and the recovery algorithm specifications, such as the recovery duration, affect packet loss, delay and jitter, and also the MTTF and MTTR for hard and soft failures. To support traffic differentiation, we suggest a priority queueing approach. We extend the results of the general queueing model and discuss four different priority queueing disciplines ranging from a pure preemptive scheme to a pure non-preemptive scheme. New disciplines increase the flexibility and decision resolution and enable the CR node to more accurately control the interaction of different classes of traffic. The models are solved, so it can be analyzed how the reliability and quality of service parameters, such as delay and jitter, for a specific class of traffic are affected not only by the channel parameters, but also by the characteristics of other traffic classes. The M/G/1 queueing model with interruptions is a foundation for performance analysis and an answer to the need of having closed-form analytical relations. We then extend the queueing model to more realistic scenarios, first with heterogeneous channels (heterogeneous service rate for different channels) and second with multiple users and a random medium access model
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