137 research outputs found
Contributions to network planning and operation of Flex-Grid/SDM optical core networks
Premi Extraordinari de Doctorat, promoció 2018-2019. Àmbit de les TICThe ever demanding bandwidth requirements for supporting emerging telecom services such as ultra-high-definition video streaming, cloud computing, connected car, virtual/augmented reality, etc., bring to the fore the necessity to upgrade continuously the technology behind transport networks in order to keep pace with this exponential traffic growth. Thus, everything seems to indicate that fixed-grid Wavelength-Division Multiplexed (WDM) networks will be upgraded by adopting a flexible-grid, thus providing finer bandwidth allocation granularities, and therefore, increasing the Grade-of-Service by packing more information in the same spectral band of standard Single-Mode Fibers (SMFs). Nevertheless, unfortunately, the fundamental Shannon’s limit of SMFs is rapidly approaching, and, then, the research efforts to increase the SMFs' capacity will be useless.
One solution to overcome this capacity crunch effect is to enable one extra dimension in addition to the frequency one, namely, the spatial dimension, thus deploying S parallel paths in order to multiply, in the best case, by S the capacity of SMF-based networks. However, additionally, it is necessary to decrease the cost and energy per bit in order to provide economically attractive solutions. For this purpose, a smooth upgrade path has to be carried out as new integrated devices and system components are developed for Space Division Multiplexing (SDM).
This thesis is concentrated on the planning and operation of the combined flexible WDM and SDM networks (i.e., Flex-Grid/SDM networks) proposing several strategies aimed at optimizing network resources usage with hardware complexity analysis. For this purpose, firstly, network problems are carefully studied and stated, and then, mathematical and/or heuristic algorithms are designed and implemented in an optical network simulator.
Specifically, after an introduction to the thesis, chapter 2 presents the background and related work. Next, chapter 3 concentrates on the study of spatially fixed Flex-Grid/SDM networks, i.e., when a rigid number of spatial channels are reserved per allocated traffic demand. In its turn, chapter 4 studies the case of Spectrally-Spatially Flexible Optical Networks (SS-FONs), as the ones providing the upper-bound network capacity. Costs and hardware requirements implied on providing this flexibility are analyzed. Network nodes aimed at reducing the cost of SS-FONs are presented and evaluated in chapter 5. Finally, this thesis ends with the presentation of the main contributions and future research work in chapter 6.La demanda de ancho de banda cada vez más exigente para soportar servicios de telecomunicaciĂłn emergentes tales como la transmisiĂłn de video de alta calidad, computaciĂłn en la nube, vehĂculo conectado, realidad virtual/aumentada, etc.…, ha puesto de manifiesto la necesidad de actualizar constantemente la tecnologĂa detrás de las redes de transporte Ăłptico con la finalidad de ir a la par de este incremento exponencial del tráfico. De esta manera, todo parece indicar que las redes basadas en la multiplexaciĂłn por division de longitud de onda (Wavelength Division Multiplexing, WDM) de ancho espectral fijo serán actualizadas adoptando un ancho de banda espectral flexible, que ofrece asignaciones de ancho de banda con granularidad más fina acorde a las demandas de tráfico; y por lo tanto, incremanta el Grado de Servicio de la red, ya que se permite acomodar mayor informaciĂłn en la misma banda espectral de las fibras monomodo (Single Mode Fibers, SMFs). Sin embargo, desafortunadamente, el lĂmite de Shannon de las fibras monomodo se está aproximando cada vez más, y cuando esto ocurra las investigaciones para incrementar la capacidad de las fibras monomodo serán infructuosas.
Una posible soluciĂłn para superar este colapso de las fibras monomodo es habilitar la dimensiĂłn espacial a más de la frecuencial, desplegando ďż˝ caminos paralelos con la finalidad de multiplicar por ďż˝ (en el mejor de los casos) la capacidad de las fibras monomodo. No obstante, es necesario disminuir el costo y la energĂa por bit con la finalidad de proveer soluciones comerciales atractivas. Para tal propĂłsito debe llevarse a cabo una actualizaciĂłn moderada conforme nuevos dispositivos y componentes integrados son desarrollados para la implementaciĂłn de la tecnologĂa basada en la multiplexaciĂłn por divisiĂłn de espacio (Space Division Multiplexing, SDM).
Esta tesis se concentra en la planificaciĂłn y operaciĂłn de la combinaciĂłn de las redes WDM flexibles y SDM (es decir, de las redes Flex-Grid/SDM) proponiendo varias estrategias dirigidas a optimizar el uso de los recursos de red junto con el análisis de la complejidad del hardware que viene acompañada. Para este fin, primeramente, los problemas de red son cuidadosamente estudiados y descritos. A continuaciĂłn, se han diseñado e implementado algoritmos basados en programaciĂłn lineal entera o heurĂsticas en un simulador de redes Ăłpticas.
DespuĂ©s de una introducciĂłn inicial, el capĂtulo 2 de esta tesis presenta el marco teĂłrico sobre los conceptos tratados y los trabajos publicados anteriormente. A continuaciĂłn, el capĂtulo 3 se concentra en el estudio de las redes Flex-Grid/SDM con la dimensiĂłn espacial rĂgida; es decir, cuando un nĂşmero fijo de canales espaciales son reservados por cada demanda de tráfico establecida. Por su parte, el capĂtulo 4 estudia las redes Flex-Grid/SDM considerando flexibilidad tanto en el dominio espacial como espectral (Spectrally and Spatially Flexible Optical Networks, SS-FONs), las cuales proveerĂan la capacidad máxima de las redes SDM. Adicionalmente, los costos y requerimientos de hardware implicados en la provisiĂłn de esta flexibilidad son analizados. El capĂtulo 5 presenta la evaluaciĂłn de nodos orientados a reducir los costos de las SS-FONs. Finalmente, el capĂtulo 6 expone las principales contribuciones y las posibles lĂneas de trabajo futuroEls requisits incessants d’ample de banda per al suport de nous serveis de telecomunicaciĂł, com poden ser la difusiĂł en directe de vĂdeo de molt alta definiciĂł, la informĂ tica en el nĂşvol, els cotxes intel·ligents connectats a la xarxa, la realitat virtual/augmentada, etc…, han exigit una millora contĂnua de les tecnologĂes de les actuals xarxes de transport de dades. Tot sembla indicar que les xarxes de transport òptiques actuals, basades en la tecnologia de multiplexaciĂł per divisiĂł de longitud d’ona (Wavelength Division Multiplexing, WDM) sobre un grid espectral rĂgid, hauran de ser reemplaçades per tecnologies òptiques mĂ©s flexibles, amb una granularitat mĂ©s fina a l’hora de suportar noves connexions, incrementat el grau de servei de les xarxes grĂ cies a aprofitament major de l’ample de banda espectral proporcionat per les fibres òptiques monomode (Single Mode Fibers, SMFs). Tanmateix, estem exhaurint ja la capacitat mĂ xima de les fibres òptiques SMF segons ens indica el lĂmit fonamental de Shannon. Per tant, qualsevol esforç enfocat a millorar la capacitat d’aquestes xarxes basades en SMFs pot acabar sent infructuĂłs.
Una possible solució per superar aquestes limitacions de capacitat és explorar la dimensió espacial, a més de l’espectral, desplegant camins en paral·lel per tal de multiplicar per , en el millor cas, la capacitat de les SMFs. Tot i això, és necessari reduir el cost i el consum energètic per bit transmès, per tal de proporcionar solucions econòmicament viables. Amb aquest propòsit, pot ser necessà ria una migració progressiva, a mesura que es desenvolupen nous dispositius i components per aquesta nova tecnologia de multiplexació per divisió espacial (Spatial Division Multiplexing, SDM).
La present tesi es centra en la planificaciĂł i operaciĂł de xarxes òptiques de nova generaciĂł que combinin tecnologies de xarxa WDM flexible i SDM (Ă©s a dir, xarxes Flex-Grid/SDM), proposant estratègies per a l’optimitzaciĂł de l’ús dels recursos de xarxa i, en definitiva, el seu cost (CapEx). Amb aquest propòsit, s’analitzen en primer moment els problemes adreçats. Tot seguit, es dissenyen algorismes per tal de solucionar-los, basats en tècniques de programaciĂł matemĂ tica i heurĂstiques, els quals s’implementen i es proven en un simulador de xarxa òptica.
DesprĂ©s d’una introducciĂł inicial, el capĂtol 2 d’aquesta tesi presenta tots els conceptes tractats i treballs relacionats publicats amb anterioritat. Tot seguit, el capĂtol 3 es centra en l’estudi de les xarxes Flex-Grid/SDM fixes en el domini espai, Ă©s a dir, on sempre es reserva un nombre rĂgid de canals espacials per qualsevol demanda suportada. El capĂtol 4 estudia les xarxes flexibles en els dominis espectrals i espacials (Spectrally-Spatially Flexible Optical Nextworks, SS-FONs), com aquelles que poden proporcionar una capacitat de xarxa mĂ xima. En aquest context, s’analitzen els requeriments en termes de cost i hardware per tal de proporcionar aquesta flexibilitat. Llavors, en el capĂtol 6 es presenten opcions de node de xarxa capaces de reduir els costos de les xarxes SS-FONs. Finalment, en el capĂtol 7 es repassen totes les contribucions de la tesi, aixĂ com posibles lĂnies de treball futurAward-winningPostprint (published version
Contribution à l'amélioration de l'efficacité des réseaux IP sur WDM en évaluant et en dépassant les limites du dimensionnement multicouche
The traffic passing through core networks grows by nearly 25% each year. To bring the costs under control, the different network layers of the network should work together to include more and more parameters during the network planning phase. This is called “multilayer network planning”. We study the multilayer network planning of static networks composed of two circuit switched layers (typically IP-over-WDM). We propose a semi-analytical model explaining the behavior of algorithms responsible for aggregation and routing in both layers. This theory allows comparing multilayer planning algorithms between them, but also explaining and enhancing their efficiency. We then describe the impact of the optical reach constraint in WDM networks on the results of a multilayer planning algorithm. Finally, we explain how these results apply to the design of future networks (dynamic and with heterogeneous optical layers)La quantité de données devant être transportée via les réseaux de cœur croit de près de 25% par an. Pour maîtriser les coûts, les différentes couches du réseau doivent mettre des informations en commun pour inclure de plus en plus de paramètres lors du dimensionnement du réseau. Cela s’appelle « dimensionnement multicouche ». Nous étudions le dimensionnement multicouche de réseaux statiques composés de deux couches utilisant la commutation en mode circuit (typiquement IP-sur-WDM). Nous proposons un modèle semi-analytique expliquant le comportement des algorithmes responsables de l’agrégation et du routage dans les deux couches. Ce cadre théorique permet de comparer les algorithmes de dimensionnement multicouche entre eux, mais aussi d’expliquer et d’améliorer leur efficience. Nous décrivons ensuite comment la contrainte de portée optique affecte les résultats d’un algorithme de dimensionnement multicouche. Enfin, nous expliquons comment ces résultats s'appliquent au dimensionnement des réseaux de nouvelle génération (dynamiques et hétérogènes en capacité optique
Resource allocation in disaggregated optical networks
The recently introduced disaggregation model is gaining interest due to its benefits when compared with traditional models.In essence, it consists on the separation of traditional hardware appliances (e.g. servers, network nodes) into commodity components, which then are mounted independently for their exploitation into customized physical infrastructures. Such an approach allows telecommunication operators and service providers to appropriately size their infrastructure and grow as needed. One of the main key benefits of the disaggregation model is the break of the vendor lock-in, pushing towards interoperability between equipment from different vendor with minimum standardization of software and hardware specifications, allowing operators to build the best solutions for their needs. Moreover, efficient scaling is also an important benefit introduced by the disaggregation approach. Due to these benefits, among others, the disaggregation model is gaining momentum and is being adopted into multiple fields and domains of nowadays telecom infrastructures. In this regard, the scenario under study of this master thesis focuses on disaggregated optical transport networks. Disaggregation allows for more open and customized optical networks, reducing both capital and operational expenditures for infrastructure owners.However, despite of these positive aspects, disaggregated optical networks face several challenges, beingthe degradation of the network performance when compared to traditional integrated solutions the most important one. In this regard, this thesis investigates the impact of disaggregation in optical networks and investigates regeneration as a potential solution to compensate the performances’ degradation. Under this premise, optimal solutions for regenerator placement, exploiting the inherent grooming capabilities of regenerators, are proposed and evaluatedIncomin
Investigation of the tolerance of wavelength-routed optical networks to traffic load variations.
This thesis focuses on the performance of circuit-switched wavelength-routed optical network with unpredictable traffic pattern variations. This characteristic of optical networks is termed traffic forecast tolerance. First, the increasing volume and heterogeneous nature of data and voice traffic is discussed. The challenges in designing robust optical networks to handle unpredictable traffic statistics are described. Other work relating to the same research issues are discussed. A general methodology to quantify the traffic forecast tolerance of optical networks is presented. A traffic model is proposed to simulate dynamic, non-uniform loads, and used to test wavelength-routed optical networks considering numerous network topologies. The number of wavelengths required and the effect of the routing and wavelength allocation algorithm are investigated. A new method of quantifying the network tolerance is proposed, based on the calculation of the increase in the standard deviation of the blocking probabilities with increasing traffic load non-uniformity. The performance of different networks are calculated and compared. The relationship between physical features of the network topology and traffic forecast tolerance is investigated. A large number of randomly connected networks with different sizes were assessed. It is shown that the average lightpath length and the number of wavelengths required for full interconnection of the nodes in static operation both exhibit a strong correlation with the network tolerance, regardless of the degree of load non-uniformity. Finally, the impact of wavelength conversion on network tolerance is investigated. Wavelength conversion significantly increases the robustness of optical networks to unpredictable traffic variations. In particular, two sparse wavelength conversion schemes are compared and discussed: distributed wavelength conversion and localized wavelength conversion. It is found that the distributed wavelength conversion scheme outperforms localized wavelength conversion scheme, both with uniform loading and in terms of the network tolerance. The results described in this thesis can be used for the analysis and design of reliable WDM optical networks that are robust to future traffic demand variations
IP/MPLS over OTN over DWDM multilayer networks: optimization models, algorithms, and analyses
Dissertation advisor: Deep MedhiVitaIncludes bibliographical references (p. 151-155)Thesis (Ph.D)--School of Computing and Engineering. University of Missouri--Kansas City, 2011Title from PDF of title page, viewed on May 24, 2011Over the past decade, multilayer network design has received significant attention
in the scientific literature. However, the explicit modeling of IP/MPLS over OTN over
DWDM in which the OTN layer is specifically considered has not been addressed before.
This multilayer network architecture has been identified as promising that bridges integration
and interaction between the IP and optical layers. In this dissertation, we consider
four related problems. First, we present an integrated capacity network optimization model for the operational
planning of such multilayer networks. The model considers the OTN layer as
a distinct layer with its unique technological ODU sublayer constraints. Secondly, we
present a design model to investigate the correlation effects of the IP and OTN layers
when the physical DWDM layer capacity is a given constant. We also develop a heuristic
algorithm to solve the models for large networks. We provide comprehensive numeric studies that consider various cost parameter
values of each layer in the network and analyze the impact of varying the values on network
layers and overall network cost. We have observed the significant impact of the
IP/MPLS capacity module on each layer and the entire network. Generally, when this
parameter size is above the average demand in the network, it leads to the best overall
network design. Thirdly, we consider the problem of optimizing node capacity in this architecture
as our design goal, since routers with more capacity and complex structure consume
significant power. We present an explicit networking optimization model that aims to
minimize the total capacity at the LSRs and the OXCs. Our assessment shows that the
different weight ratios of LSR to OXC nodes do not generally affect the overall required
capacity of each layer. However, the weight ratios influence differently required node
capacity at nodes in each layer. Finally, we factor in the survivability of the multilayer network by considering a
suitable protection mechanism for each network layer. We provide a phase-based heuristic
approach, study and analysis. We have also examined the network performance from
cost vs. protection capacity perspectives while varying the size of the IP/MPLS capacity
module.Introduction -- Literature survey -- OTN technology overview -- An integrated capacity optimization model -- A heuristic approach to solve (P1) -- Study and results for (P1) -- IP/MPLS and OTN layer correlation effects -- Study and results for (P2) -- Optimizing node capacity -- Study and results of (P3) -- Multilayer network protection -- Study and results for (P4) -- conclusion and future work -- Appendix A. Sample input/output file
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