Integrated mechanisms for QoS and restoration in mesh transport networks

Survivable networks have the capability to survive from the events of network components failures. The resilience mechanisms in these networks protect and restore the impaired communication paths by using spare capacity. On the other hand, Quality of Service (QoS) mechanisms focus on network capabilities that provide the facilities to differentiate network traffic and offer different levels of service to each class of traffic. Traditionally the survivability algorithms were applied at the physical (optical) layer, whereas the QoS mechanisms mainly applied at packet-forwarding level. Recent technological breakthroughs can now facilitate novel forwarding techniques for optical data bursts that make it possible to capture packets at the optical layer. A major challenge in the transfer of these ultrahigh-speed data bursts is to allocate resources according to QoS specifications and to provide spare capacity required to address link failures

Lightpath routing with survivability requirements in WDM optical mesh networks

Ph.DDOCTOR OF PHILOSOPH

Dynamic routing of reliability-differentiated connections in WDM optical networks

Master'sMASTER OF ENGINEERIN

Optimization of p-cycle protection schemes in optical networks

La survie des réseaux est un domaine d'étude technique très intéressant ainsi qu'une préoccupation critique dans la conception des réseaux. Compte tenu du fait que de plus en plus de données sont transportées à travers des réseaux de communication, une simple panne peut interrompre des millions d'utilisateurs et engendrer des millions de dollars de pertes de revenu. Les techniques de protection des réseaux consistent à fournir une capacité supplémentaire dans un réseau et à réacheminer les flux automatiquement autour de la panne en utilisant cette disponibilité de capacité. Cette thèse porte sur la conception de réseaux optiques intégrant des techniques de survie qui utilisent des schémas de protection basés sur les p-cycles. Plus précisément, les p-cycles de protection par chemin sont exploités dans le contexte de pannes sur les liens. Notre étude se concentre sur la mise en place de structures de protection par p-cycles, et ce, en supposant que les chemins d'opération pour l'ensemble des requêtes sont définis a priori. La majorité des travaux existants utilisent des heuristiques ou des méthodes de résolution ayant de la difficulté à résoudre des instances de grande taille. L'objectif de cette thèse est double. D'une part, nous proposons des modèles et des méthodes de résolution capables d'aborder des problèmes de plus grande taille que ceux déjà présentés dans la littérature. D'autre part, grâce aux nouveaux algorithmes, nous sommes en mesure de produire des solutions optimales ou quasi-optimales. Pour ce faire, nous nous appuyons sur la technique de génération de colonnes, celle-ci étant adéquate pour résoudre des problèmes de programmation linéaire de grande taille. Dans ce projet, la génération de colonnes est utilisée comme une façon intelligente d'énumérer implicitement des cycles prometteurs. Nous proposons d'abord des formulations pour le problème maître et le problème auxiliaire ainsi qu'un premier algorithme de génération de colonnes pour la conception de réseaux protegées par des p-cycles de la protection par chemin. L'algorithme obtient de meilleures solutions, dans un temps raisonnable, que celles obtenues par les méthodes existantes. Par la suite, une formulation plus compacte est proposée pour le problème auxiliaire. De plus, nous présentons une nouvelle méthode de décomposition hiérarchique qui apporte une grande amélioration de l'efficacité globale de l'algorithme. En ce qui concerne les solutions en nombres entiers, nous proposons deux méthodes heurisiques qui arrivent à trouver des bonnes solutions. Nous nous attardons aussi à une comparaison systématique entre les p-cycles et les schémas classiques de protection partagée. Nous effectuons donc une comparaison précise en utilisant des formulations unifiées et basées sur la génération de colonnes pour obtenir des résultats de bonne qualité. Par la suite, nous évaluons empiriquement les versions orientée et non-orientée des p-cycles pour la protection par lien ainsi que pour la protection par chemin, dans des scénarios de trafic asymétrique. Nous montrons quel est le coût de protection additionnel engendré lorsque des systèmes bidirectionnels sont employés dans de tels scénarios. Finalement, nous étudions une formulation de génération de colonnes pour la conception de réseaux avec des p-cycles en présence d'exigences de disponibilité et nous obtenons des premières bornes inférieures pour ce problème.Network survivability is a very interesting area of technical study and a critical concern in network design. As more and more data are carried over communication networks, a single outage can disrupt millions of users and result in millions of dollars of lost revenue. Survivability techniques involve providing some redundant capacity within the network and automatically rerouting traffic around the failure using this redundant capacity. This thesis concerns the design of survivable optical networks using p-cycle based schemes, more particularly, path-protecting p-cycles, in link failure scenarios. Our study focuses on the placement of p-cycle protection structures assuming that the working routes for the set of connection requests are defined a priori. Most existing work carried out on p-cycles concerns heuristic algorithms or methods suffering from critical lack of scalability. Thus, the objective of this thesis is twofold: on the one hand, to propose scalable models and solution methods enabling to approach larger problem instances and on the other hand, to produce 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. Here, column generation is used as an intelligent way of implicitly enumerating promising cycles to be part of p-cycle designs. At first, we propose mathematical formulations for the master and the pricing problems as well as the first column generation algorithm for the design of survivable networks based on path-protecting p-cycles. The resulting algorithm obtains better solutions within reasonable running time in comparison with existing methods. Then, a much more compact formulation of the pricing problem is obtained. In addition, we also propose a new hierarchical decomposition method which greatly improves the efficiency of the whole algorithm and allows us to solve larger problem instances. As for integer solutions, two heuristic approaches are proposed to obtain good solutions. Next, we dedicate our attention to a systematic comparison of p-cycles and classical shared protection schemes. We perform an accurate comparison by using a unified column generation framework to find provably good results. Afterwards, our study concerns an empirical evaluation of directed and undirected link- and path-protecting p-cycles under asymmetric traffic scenarios. We show how much additional protection cost results from employing bidirectional systems in such scenarios. Finally, we investigate a column generation formulation for the design of p-cycle networks under availability requirements and obtain the first lower bounds for the problem

Survivability stategies in all optical networks.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2006.Thesis (M.Sc.)-University of KwaZulu-Natal, 2006.Recent advances in fiber optics technology have enabled extremely high-speed transport of different forms of data, on multiple wavelengths of an optical fiber, using Dense Wavelength Division Multiplexing (DWDM). It has now become possible to deploy high-speed, multi-service networks using DWDM technology. As the amount of traffic carried has increased, any single failure can be catastrophic. Survivability becomes indispensable in such networks. Therefore, it is imperative to design networks that can quickly and efficiently recover from failures. Most research to date in survivable optical network design and operation focuses on single link failures, however, the occurrence of multiple-link failures are not uncommon in networks today. Multi-link failure scenarios can arise out of two common situations. First, an arbitrary link may fail in the network, and before that link can be repaired, another link fails, thus creating a multi-link failure sequence. Secondly, it might happen in practice that two distinct physical links may be routed via the same common duct or physical channel. A failure at that shared physical location creates a logical multiple-link failure. In this dissertation, we conduct an intensive study of mechanisms for achieving survivability in optical networks. From the many mechanisms presented in the literature the focus of this work was on protection as a mechanism of survivability. In particular four protection schemes were simulated and their results analyzed to ascertain which protection scheme achieves the best survivability in terms of number of wavelengths recovered for a specific failure scenario. A model network was chosen and the protection schemes were evaluated for both single and multiple link and node failures. As an indicator of the performance of these protection schemes over a period of time average service availability and average loss in traffic for each protection scheme was also simulated. Further simulations were conducted to observe the percentage link and node utilization of each scheme hence allowing us to determine the strain each protection scheme places on network resources when traffic in the network increases. Finally based on these simulation results, recommendations of which protection scheme and under what failure conditions they should be used are made.Recent advances in fiber optics technology have enabled extremely high-speed transpor

Optimización metaheurística para la planificación de redes WDM

Las implementaciones actuales de las redes de telecomunicaciones no permiten soportar el incremento en la demanda de ancho de banda producido por el crecimiento del tráfico de datos en las últimas décadas. La aparición de la fibra óptica y el desarrollo de la tecnología de multiplexación por división de longitudes de onda (WDM) permite incrementar la capacidad de redes de telecomunicaciones existentes mientras se minimizan costes. En este trabajo se planifican redes ópticas WDM mediante la resolución de los problemas de Provisión y Conducción en redes WDM (Provisioning and Routing Problem) y de Supervivencia (Survivability Problem). El Problema de Conducción y Provisión consiste en incrementar a mínimo coste la capacidad de una red existente de tal forma que se satisfaga un conjunto de requerimientos de demanda. El problema de supervivencia consiste en garantizar el flujo del tráfico a través de una red en caso de fallo de alguno de los elementos de la misma. Además se resuelve el Problema de Provisión y Conducción en redes WDM con incertidumbre en las demandas. Para estos problemas se proponen modelos de programación lineal entera. Las metaheurísticas proporcionan un medio para resolver problemas de optimización complejos, como los que surgen al planificar redes de telecomunicaciones, obteniendo soluciones de alta calidad en un tiempo computacional razonable. Las metaheurísticas son estrategias que guían y modifican otras heurísticas para obtener soluciones más allá de las generadas usualmente en la búsqueda de optimalidad local. No garantizan que la mejor solución encontrada, cuando se satisfacen los criterios de parada, sea una solución óptima global del problema. Sin embargo, la experimentación de implementaciones metaheurísticas muestra que las estrategias de búsqueda embebidas en tales procedimientos son capaces de encontrar soluciones de alta calidad a problemas difíciles en industria, negocios y ciencia. Para la solución del problema de Provisión y Conducción en Redes WDM, se desarrolla un algoritmo metaheurístico híbrido que combina principalmente ideas de las metaheurísticas Búsqueda Dispersa (Scatter Search) y Búsqueda Mutiarranque (Multistart). Además añade una componente tabú en uno de los procedimiento del algoritmo. Se utiliza el modelo de programación lineal entera propuesto por otros autores y se propone un modelo de programación lineal entera alternativo que proporciona cotas superiores al problema, pero incluye un menor número de variables y restricciones, pudiendo ser resuelto de forma óptima para tamaños de red mayores. Los resultados obtenidos por el algoritmo metaheurístico diseñado se comparan con los obtenidos por un procedimiento basado en permutaciones de las demandas propuesto anteriormente por otros autores, y con los dos modelos de programación lineal entera usados. Se propone modelos de programación lineal entera para sobrevivir la red en caso de fallos en un único enlace. Se proponen modelos para los esquemas de protección de enlace compartido, de camino compartido con enlaces disjuntos, y de camino compartido sin enlaces disjuntos. Se propone un método de resolución metaheurístico que obtiene mejores costes globales que al resolver el problema en dos fases, es decir, al resolver el problema de servicio y a continuación el de supervivencia. Se proponen además modelos de programación entera para resolver el problema de provisión en redes WDM con incertidumbres en las demandas

Resilient virtual topologies in optical networks and clouds

Optical networks play a crucial role in the development of Internet by providing a high speed infrastructure to cope with the rapid expansion of high bandwidth demand applications such as video, HDTV, teleconferencing, cloud computing, and so on. Network virtualization has been proposed as a key enabler for the next generation networks and the future Internet because it allows diversification the underlying architecture of Internet and lets multiple heterogeneous network architectures coexist. Physical network failures often come from natural disasters or human errors, and thus cannot be fully avoided. Today, with the increase of network traffic and the popularity of virtualization and cloud computing, due to the sharing nature of network virtualization, one single failure in the underlying physical network can affect thousands of customers and cost millions of dollars in revenue. Providing resilience for virtual network topology over optical network infrastructure thus becomes of prime importance. This thesis focuses on resilient virtual topologies in optical networks and cloud computing. We aim at finding more scalable models to solve the problem of designing survivable logical topologies for more realistic and meaningful network instances while meeting the requirements on bandwidth, security, as well as other quality of service such as recovery time. To address the scalability issue, we present a model based on a column generation decomposition. We apply the cutset theorem with a decomposition framework and lazy constraints. We are able to solve for much larger network instances than the ones in literature. We extend the model to address the survivability problem in the context of optical networks where the characteristics of optical networks such as lightpaths and wavelength continuity and traffic grooming are taken into account. We analyze and compare the bandwidth requirement between the two main approaches in providing resiliency for logical topologies. In the first approach, called optical protection, the resilient mechanism is provided by the optical layer. In the second one, called logical restoration, the resilient mechanism is done at the virtual layer. Next, we extend the survivability problem into the context of cloud computing where the major complexity arises from the anycast principle. We are able to solve the problem for much larger network instances than in the previous studies. Moreover, our model is more comprehensive that takes into account other QoS criteria, such that recovery time and delay requirement