Sub-Graph p-cycle formation for span failures in all-Optical Networks

p-Cycles offer ring-like switching speed and mesh-like spare capacity efficiency for protecting network against link failures. This makes them extremely efficient and effective protection technique. p-Cycles can also protect all the links in a network against simultaneous failures of multiple links. But it has been mostly studied for single link failure scenarios in the networks with the objective to minimize spare capacity under the condition of100% restorability. For large networks, use of p-cycles is difficult because their optimization requires an excessive amount of time as the number of variables in the corresponding Integer Linear Program (ILP) increase with the increase in the network size. In a real-time network situation,setting up a highly efficient protection in a short time is essential.Thus, we introduce a network sub-graphing approach, in which a network is segmented into smaller parts based on certain network attributes. Then, an optimal solution is found for each sub-graph. Finally, the solutions for all the sub-graphs is combined to get a sub-optimal solution for the whole network. We achieved better computational efficiency at the expense of marginal spare capacity increases with this approach

Next-Generation Transport Networks Leveraging Universal Traffic Switching and Flexible Optical Transponders

Recent developments in communication technology contributed to the growth of network traffic exponentially. Cost per bit has to necessarily suffer an inverse trend, posing several challenges to network operators. Optical transport networks are no exception to this. On one hand, they have to keep up with the expectations of data speed, volume, and growth at the agreed quality-of-service (QoS), while on the other hand, a steep downward trend of the cost per bit is a matter of concern. Thus, the proper selection of network architecture, technology, resiliency schemes, and traffic handling contributes to the total cost of ownership (TCO). In this context, this chapter looks into the network architectures, including the optical transport network (OTN) switch (both traditional and universal), resiliency schemes (protection and restoration), flexible-rate line interfaces, and an overall strategy of handover in between metro and core networks. A design framework is also described and used to support the case studies reported in this chapter

Survivability aspects of future optical backbone networks

In huidige glasvezelnetwerken kan een enkele vezel een gigantische hoeveelheid data dragen, ruwweg het equivalent van 25 miljoen gelijktijdige telefoongesprekken. Hierdoor zullen netwerkstoringen, zoals breuken van een glasvezelkabel, de communicatie van een groot aantal eindgebruikers verstoren. Netwerkoperatoren kiezen er dan ook voor om hun netwerk zo te bouwen dat zulke grote storingen automatisch opgevangen worden. Dit proefschrift spitst zich toe op twee aspecten rond de overleefbaarheid in toekomstige optische netwerken. De eerste doelstelling die beoogd wordt is het tot stand brengen vanrobuuste dataverbindingen over meerdere netwerken. Door voldoende betrouwbare verbindingen tot stand te brengen over een infrastructuur die niet door een enkele entiteit wordt beheerd kan men bv. weredwijd Internettelevisie van hoge kwaliteit aanbieden. De bestudeerde oplossing heeft niet enkel tot doel om deze zeer betrouwbare verbinding te berekenen, maar ook om dit te bewerkstelligen met een minimum aan gebruikte netwerkcapaciteit. De tweede doelstelling was om een antwoord te formuleren om de vraag hoe het toepassen van optische schakelsystemen gebaseerd op herconfigureerbare optische multiplexers een impact heeft op de overleefbaarheid van een optisch netwerk. Bij lagere volumes hebben optisch geschakelde netwerken weinig voordeel van dergelijke gesofistikeerde methoden. Elektronisch geschakelde netwerken vertonen geen afhankelijkheid van het datavolume en hebben altijd baat bij optimalisatie

Design and provisioning of WDM networks for traffic grooming

Wavelength Division Multiplexing (WDM) is the most viable technique for utilizing the enormous amounts of bandwidth inherently available in optical fibers. However, the bandwidth offered by a single wavelength in WDM networks is on the order of tens of Gigabits per second, while most of the applications\u27 bandwidth requirements are still subwavelength. Therefore, cost-effective design and provisioning of WDM networks require that traffic from different sessions share bandwidth of a single wavelength by employing electronic multiplexing at higher layers. This is known as traffic grooming. Optical networks supporting traffic grooming are usually designed in a way such that the cost of the higher layer equipment used to support a given traffic matrix is reduced. In this thesis, we propose a number of optimal and heuristic solutions for the design and provisioning of optical networks for traffic grooming with an objective of network cost reduction. In doing so, we address several practical issues. Specifically, we address the design and provisioning of WDM networks on unidirectional and bidirectional rings for arbitrary unicast traffic grooming, and on mesh topologies for arbitrary multipoint traffic grooming. In multipoint traffic grooming, we address both multicast and many-to-one traffic grooming problems. We provide a unified frame work for optimal and approximate network dimensioning and channel provisioning for the generic multicast traffic grooming problem, as well as some variants of the problem. For many-to-one traffic grooming we propose optimal as well as heuristic solutions. Optimal formulations which are inherently non-linear are mapped to an optimal linear formulation. In the heuristic solutions, we employ different problem specific search strategies to explore the solution space. We provide a number of experimental results to show the efficacy of our proposed techniques for the traffic grooming problem in WDM networks

End-to-end shared restoration in multi-domain networks / by Zhiying Gao.

Emerging multi-service data applications require high-bandwidth high-quality connectivity across multiple network domains, each of which is generally controlled by an independent service provider. These applications necessitate the need for highly intelligent survivable routing mechanisms to compute end-to-end paths and to perform functions of protection and bandwidth management across multiple domains. On the other hand, current protection and restoration mechanisms focus on the network survivability inside a single domain network. Powerful dynamic protection and restoration algorithms have been developed for single-domain networks. The majority of these algorithms are based on the exchange of detailed link-state information among the nodes, which makes them less attractive to networks with multiple domains where link-state information needs to be abstracted within each domain for efficiency and scalability reasons. To address this problem, we present two network information abstraction models designed to aggregate link-state information within each domain and only to advertise the aggregated information to other domains. The first abstraction model is referred to as virtual path abstraction model, with which every domain is abstracted as a set of border-nodes interconnected by virtual paths. The multi-domain network is then topologically aggregated to become a single-domain network, called virtual path network, which consists of border-nodes interconnected internally by virtual paths and externally by inter-domain links. The second abstraction model is referred to as virtual node model, with which every domain is modeled as a virtual node with a certain internal minimum capacity that can be advertised to other domains. The multi-domain network is then topologically aggregated to become a single-domain network, called virtual node network, consisting of virtual nodes interconnected by inter-domain links. We have designed and developed three distributed end-to-end shared restoration schemes based on the information abstraction models presented above. These three schemes are referred to as Link Disjointed Virtual Path (LDVP) restoration. Domain Disjointed Virtual Path (DDVP) restoration, and Link Disjointed Virtual Node (LDVN) restoration. The LDVP and LDVN schemes are designed to provide link diversity between the primary and backup paths of each demand, whereas the DDVP scheme is designed to compute a pair of domain-disjointed paths for the demand. We show that the proposed schemes are more scalable than the existing restoration schemes because they require less amount of link-state information to be advertised between the domains. This will reduce the routing message overhead and make the proposed schemes to be scalable to large multi-domain networks. We also evaluate the performance o f the proposed schemes in terms of capacity usage and restoration time through simulation experiments on two multi-domain networks; one is based on the NSF (National Science Foundation) network, and the other is based on the European Optical Network. The simulation results show that the proposed schemes save the backup bandwidth significantly because of the sharing of backup resources among failure-disjointed connections. The simulation results also show that the restoration time achieved by the proposed restoration schemes (over the multi-domain network) is around or less than 60 ms, which is within the range accepted in today’s networks

Ethernet - a survey on its fields of application

During the last decades, Ethernet progressively became the most widely used local area networking (LAN) technology. Apart from LAN installations, Ethernet became also attractive for many other fields of application, ranging from industry to avionics, telecommunication, and multimedia. The expanded application of this technology is mainly due to its significant assets like reduced cost, backward-compatibility, flexibility, and expandability. However, this new trend raises some problems concerning the services of the protocol and the requirements for each application. Therefore, specific adaptations prove essential to integrate this communication technology in each field of application. Our primary objective is to show how Ethernet has been enhanced to comply with the specific requirements of several application fields, particularly in transport, embedded and multimedia contexts. The paper first describes the common Ethernet LAN technology and highlights its main features. It reviews the most important specific Ethernet versions with respect to each application field’s requirements. Finally, we compare these different fields of application and we particularly focus on the fundamental concepts and the quality of service capabilities of each proposal

Domain/Multi-Domain Protection and Provisioning in Optical Networks

L’évolution récente des commutateurs de sélection de longueurs d’onde (WSS -Wavelength Selective Switch) favorise le développement du multiplexeur optique d’insertionextraction reconfigurable (ROADM - Reconfigurable Optical Add/Drop Multiplexers) à plusieurs degrés sans orientation ni coloration, considéré comme un équipement fort prometteur pour les réseaux maillés du futur relativement au multiplexage en longueur d’onde (WDM -Wavelength Division Multiplexing ). Cependant, leur propriété de commutation asymétrique complique la question de l’acheminement et de l’attribution des longueur d’ondes (RWA - Routing andWavelength Assignment). Or la plupart des algorithmes de RWA existants ne tiennent pas compte de cette propriété d’asymétrie. L’interruption des services causée par des défauts d’équipements sur les chemins optiques (résultat provenant de la résolution du problème RWA) a pour conséquence la perte d’une grande quantité de données. Les recherches deviennent ainsi incontournables afin d’assurer la survie fonctionnelle des réseaux optiques, à savoir, le maintien des services, en particulier en cas de pannes d’équipement. La plupart des publications antérieures portaient particulièrement sur l’utilisation d’un système de protection permettant de garantir le reroutage du trafic en cas d’un défaut d’un lien. Cependant, la conception de la protection contre le défaut d’un lien ne s’avère pas toujours suffisante en termes de survie des réseaux WDM à partir de nombreux cas des autres types de pannes devenant courant de nos jours, tels que les bris d’équipements, les pannes de deux ou trois liens, etc. En outre, il y a des défis considérables pour protéger les grands réseaux optiques multidomaines composés de réseaux associés à un domaine simple, interconnectés par des liens interdomaines, où les détails topologiques internes d’un domaine ne sont généralement pas partagés à l’extérieur. La présente thèse a pour objectif de proposer des modèles d’optimisation de grande taille et des solutions aux problèmes mentionnés ci-dessus. Ces modèles-ci permettent de générer des solutions optimales ou quasi-optimales avec des écarts d’optimalité mathématiquement prouvée. Pour ce faire, nous avons recours à la technique de génération de colonnes afin de résoudre les problèmes inhérents à la programmation linéaire de grande envergure. Concernant la question de l’approvisionnement dans les réseaux optiques, nous proposons un nouveau modèle de programmation linéaire en nombres entiers (ILP - Integer Linear Programming) au problème RWA afin de maximiser le nombre de requêtes acceptées (GoS - Grade of Service). Le modèle résultant constitue celui de l’optimisation d’un ILP de grande taille, ce qui permet d’obtenir la solution exacte des instances RWA assez grandes, en supposant que tous les noeuds soient asymétriques et accompagnés d’une matrice de connectivité de commutation donnée. Ensuite, nous modifions le modèle et proposons une solution au problème RWA afin de trouver la meilleure matrice de commutation pour un nombre donné de ports et de connexions de commutation, tout en satisfaisant/maximisant la qualité d’écoulement du trafic GoS. Relativement à la protection des réseaux d’un domaine simple, nous proposons des solutions favorisant la protection contre les pannes multiples. En effet, nous développons la protection d’un réseau d’un domaine simple contre des pannes multiples, en utilisant les p-cycles de protection avec un chemin indépendant des pannes (FIPP - Failure Independent Path Protecting) et de la protection avec un chemin dépendant des pannes (FDPP - Failure Dependent Path-Protecting). Nous proposons ensuite une nouvelle formulation en termes de modèles de flots pour les p-cycles FDPP soumis à des pannes multiples. Le nouveau modèle soulève un problème de taille, qui a un nombre exponentiel de contraintes en raison de certaines contraintes d’élimination de sous-tour. Par conséquent, afin de résoudre efficacement ce problème, on examine : (i) une décomposition hiérarchique du problème auxiliaire dans le modèle de décomposition, (ii) des heuristiques pour gérer efficacement le grand nombre de contraintes. À propos de la protection dans les réseaux multidomaines, nous proposons des systèmes de protection contre les pannes d’un lien. Tout d’abord, un modèle d’optimisation est proposé pour un système de protection centralisée, en supposant que la gestion du réseau soit au courant de tous les détails des topologies physiques des domaines. Nous proposons ensuite un modèle distribué de l’optimisation de la protection dans les réseaux optiques multidomaines, une formulation beaucoup plus réaliste car elle est basée sur l’hypothèse d’une gestion de réseau distribué. Ensuite, nous ajoutons une bande pasiv sante partagée afin de réduire le coût de la protection. Plus précisément, la bande passante de chaque lien intra-domaine est partagée entre les p-cycles FIPP et les p-cycles dans une première étude, puis entre les chemins pour lien/chemin de protection dans une deuxième étude. Enfin, nous recommandons des stratégies parallèles aux solutions de grands réseaux optiques multidomaines. Les résultats de l’étude permettent d’élaborer une conception efficace d’un système de protection pour un très large réseau multidomaine (45 domaines), le plus large examiné dans la littérature, avec un système à la fois centralisé et distribué.Recent developments in the wavelength selective switch (WSS) technology enable multi-degree reconfigurable optical add/drop multiplexers (ROADM) architectures with colorless and directionless switching, which is regarded as a very promising enabler for future reconfigurable wavelength division multiplexing (WDM) mesh networks. However, its asymmetric switching property complicates the optimal routing and wavelength assignment (RWA) problem, which is NP-hard. Most of the existing RWA algorithms do not consider such property. Disruption of services through equipment failures on the lightpaths (output of RWA problem) is consequential as it involves the lost of large amounts of data. Therefore, substantial research efforts are needed to ensure the functional survivability of optical networks, i.e., the continuation of services even when equipment failures occur. Most previous publications have focused on using a protection scheme to guarantee the traffic connections in the event of single link failures. However, protection design against single link failures turns out not to be always sufficient to keep the WDM networks away from many downtime cases as other kinds of failures, such as node failures, dual link failures, triple link failures, etc., become common nowadays. Furthermore, there are challenges to protect large multi-domain optical networks which are composed of several singledomain networks, interconnected by inter-domain links, where the internal topological details of a domain are usually not shared externally. The objective of this thesis is to propose scalable models and solution methods for the above problems. The models enable to approach large problem instances while producing optimal or near optimal solutions with mathematically proven optimality gaps. For this, we rely on the column generation technique which is suitable to solve large scale linear programming problems. For the provisioning problem in optical networks, we propose a new ILP (Integer Linear Programming) model for RWA problem with the objective of maximizing the Grade of Service (GoS). The resulting model is a large scale optimization ILP model, which allows the exact solution of quite large RWA instances, assuming all nodes are asymmetric and with a given switching connectivity matrix. Next, we modify the model and propose a solution for the RWA problem with the objective of finding the best switching connectivity matrix for a given number of ports and a given number of switching connections, while satisfying/maximizing the GoS. For protection in single domain networks, we propose solutions for the protection against multiple failures. Indeed, we extent the protection of a single domain network against multiple failures, using FIPP and FDPP p-cycles. We propose a new generic flow formulation for FDPP p-cycles subject to multiple failures. Our new model ends up with a complex pricing problem, which has an exponential number of constraints due to some subtour elimination constraints. Consequently, in order to efficiently solve the pricing problem, we consider: (i) a hierarchical decomposition of the original pricing problem; (ii) heuristics in order to go around the large number of constraints in the pricing problem. For protection in multi-domain networks, we propose protection schemes against single link failures. Firstly, we propose an optimization model for a centralized protection scheme, assuming that the network management is aware of all the details of the physical topologies of the domains. We then propose a distributed optimization model for protection in multi-domain optical networks, a much more realistic formulation as it is based on the assumption of a distributed network management. Then, we add bandwidth sharing in order to reduce the cost of protection. Bandwidth of each intra-domain link is shared among FIPP p-cycles and p-cycles in a first study, and then among paths for link/path protection in a second study. Finally, we propose parallel strategies in order to obtain solutions for very large multi-domain optical networks. The result of this last study allows the efficent design of a protection scheme for a very large multi-domain network (45 domains), the largest one by far considered in the literature, both with a centralized and distributed scheme

Algorithms for advance bandwidth reservation in media production networks

Media production generally requires many geographically distributed actors (e.g., production houses, broadcasters, advertisers) to exchange huge amounts of raw video and audio data. Traditional distribution techniques, such as dedicated point-to-point optical links, are highly inefficient in terms of installation time and cost. To improve efficiency, shared media production networks that connect all involved actors over a large geographical area, are currently being deployed. The traffic in such networks is often predictable, as the timing and bandwidth requirements of data transfers are generally known hours or even days in advance. As such, the use of advance bandwidth reservation (AR) can greatly increase resource utilization and cost efficiency. In this paper, we propose an Integer Linear Programming formulation of the bandwidth scheduling problem, which takes into account the specific characteristics of media production networks, is presented. Two novel optimization algorithms based on this model are thoroughly evaluated and compared by means of in-depth simulation results