609 research outputs found

    Performance improvement of an optical network providing services based on multicast

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    Operators of networks covering large areas are confronted with demands from some of their customers who are virtual service providers. These providers may call for the connectivity service which fulfils the specificity of their services, for instance a multicast transition with allocated bandwidth. On the other hand, network operators want to make profit by trading the connectivity service of requested quality to their customers and to limit their infrastructure investments (or do not invest anything at all). We focus on circuit switching optical networks and work on repetitive multicast demands whose source and destinations are {\em \`a priori} known by an operator. He may therefore have corresponding trees "ready to be allocated" and adapt his network infrastructure according to these recurrent transmissions. This adjustment consists in setting available branching routers in the selected nodes of a predefined tree. The branching nodes are opto-electronic nodes which are able to duplicate data and retransmit it in several directions. These nodes are, however, more expensive and more energy consuming than transparent ones. In this paper we are interested in the choice of nodes of a multicast tree where the limited number of branching routers should be located in order to minimize the amount of required bandwidth. After formally stating the problem we solve it by proposing a polynomial algorithm whose optimality we prove. We perform exhaustive computations to show an operator gain obtained by using our algorithm. These computations are made for different methods of the multicast tree construction. We conclude by giving dimensioning guidelines and outline our further work.Comment: 16 pages, 13 figures, extended version from Conference ISCIS 201

    Le problÚme de l'arborescence de Steiner dans les réseaux tout-optiques

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    International audienceConnaissant un graphe orientĂ© contenant n noeuds et des arcs pondĂ©rĂ©s positivement, possĂ©dant une racine r et un ensemble X de k noeuds appelĂ©s terminaux, le problĂšme de l'arborescence de Steiner (Directed Steiner Tree ou DST) consiste Ă  calculer une arborescence de poids minimal enracinĂ©e en r couvrant tous les terminaux. Ce problĂšme est adaptĂ© pour modĂ©liser la diffusion multicast dans un rĂ©seau quand celui ci ne contient aucun noeud dit non diffusant. Un tel noeud est incapable de copier une donnĂ©e qu'il reçoit. Il est donc dans l'obligation pour transfĂ©rer cette donnĂ©e Ă  plusieurs destinataires de la recevoir plusieurs fois. Le poids de son arc entrant est donc dĂ©multipliĂ©. La prĂ©sence de noeuds non diffusants est visible par exemple dans un type de rĂ©seaux, dits tout-optiques, oĂč tant que le paquet est encodĂ© sous forme optique, il ne peut ĂȘtre dirigĂ© que vers un seul destinataire. On s'intĂ©resse Ă  une gĂ©nĂ©ralisation de DST, nommĂ©e Arborescence de Steiner Ă  Branchement Contraint (ASBC) modĂ©lisant ce problĂšme de multicast dans le cas d'un rĂ©seau oĂč le nombre de noeuds diffusants est limitĂ© par un entier d. Nous montrons que ce problĂšme est XP quand il est paramĂ©trĂ© par d. Nous montrons Ă©galement qu'il est possible de construire, Ă  l'aide de ASBC, une |k-1/d|-approximation XP en d pour le problĂšme DST. Enfin, nous montrons que le problĂšme ASBC, sous contrainte que NP n'est pas inclus dans DTIME[n^(O(loglog n))], ne peut ĂȘtre approchĂ© polynomialement avec un rapport 1 + (1/e - epsilon) k/(d-1)$, quelque soit epsilon > 0

    Atomic-SDN: Is Synchronous Flooding the Solution to Software-Defined Networking in IoT?

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    The adoption of Software Defined Networking (SDN) within traditional networks has provided operators the ability to manage diverse resources and easily reconfigure networks as requirements change. Recent research has extended this concept to IEEE 802.15.4 low-power wireless networks, which form a key component of the Internet of Things (IoT). However, the multiple traffic patterns necessary for SDN control makes it difficult to apply this approach to these highly challenging environments. This paper presents Atomic-SDN, a highly reliable and low-latency solution for SDN in low-power wireless. Atomic-SDN introduces a novel Synchronous Flooding (SF) architecture capable of dynamically configuring SF protocols to satisfy complex SDN control requirements, and draws from the authors' previous experiences in the IEEE EWSN Dependability Competition: where SF solutions have consistently outperformed other entries. Using this approach, Atomic-SDN presents considerable performance gains over other SDN implementations for low-power IoT networks. We evaluate Atomic-SDN through simulation and experimentation, and show how utilizing SF techniques provides latency and reliability guarantees to SDN control operations as the local mesh scales. We compare Atomic-SDN against other SDN implementations based on the IEEE 802.15.4 network stack, and establish that Atomic-SDN improves SDN control by orders-of-magnitude across latency, reliability, and energy-efficiency metrics

    Optimizing Network Coding Algorithms for Multiple Applications.

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    Deviating from the archaic communication approach of treating information as a fluid moving through pipes, the concepts of Network Coding (NC) suggest that optimal throughput of a multicast network can be achieved by processing information at individual network nodes. However, existing challenges to harness the advantages of NC concepts for practical applications have prevented the development of NC into an effective solution to increase the performance of practical communication networks. In response, the research work presented in this thesis proposes cross-layer NC solutions to increase the network throughput of data multicast as well as video quality of video multicast applications. First, three algorithms are presented to improve the throughput of NC enabled networks by minimizing the NC coefficient vector overhead, optimizing the NC redundancy allocation and improving the robustness of NC against bursty packet losses. Considering the fact that majority of network traffic occupies video, rest of the proposed NC algorithms are content-aware and are optimized for both data and video multicast applications. A set of content and network-aware optimization algorithms, which allocate redundancies for NC considering content properties as well as the network status, are proposed to efficiently multicast data and video across content delivery networks. Furthermore content and channel-aware joint channel and network coding algorithms are proposed to efficiently multicast data and video across wireless networks. Finally, the possibilities of performing joint source and network coding are explored to increase the robustness of high volume video multicast applications. Extensive simulation studies indicate significant improvements with the proposed algorithms to increase the network throughput and video quality over related state-of-the-art solutions. Hence, it is envisaged that the proposed algorithms will contribute to the advancement of data and video multicast protocols in the future communication networks

    Measurement Based Reconfigurations in Optical Ring Metro Networks

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    Single-hop wavelength division multiplexing (WDM) optical ring networks operating in packet mode are one of themost promising architectures for the design of innovative metropolitan network (metro) architectures. They permit a cost-effective design, with a good combination of optical and electronic technologies, while supporting features like restoration and reconfiguration that are essential in any metro scenario. In this article, we address the tunability requirements that lead to an effective resource usage and permit reconfiguration in optical WDM metros.We introduce reconfiguration algorithms that, on the basis of traffic measurements, adapt the network configuration to traffic demands to optimize performance. Using a specific network architecture as a reference case, the paper aims at the broader goal of showing which are the advantages fostered by innovative network designs exploiting the features of optical technologies
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