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

Algorithms for Finding Diameter Cycles of Biconnected Graphs

In this paper, we first coin a new graph theoretic problem called the diameter cycle problem with numerous applications. A longest cycle in a graph G = (V, E) is referred to as a diameter cycle of G iff the distance in G of every vertex on the cycle to the rest of the on-cycle vertices is maximal. We then present two algorithms for finding a diameter cycle of a biconnected graph. The first algorithm is an abstract intuitive algorithm that utilizes a brute-force mechanism for expanding an initial cycle by repeatedly replacing paths on the cycle with longer paths. The second algorithm is a concrete algorithm that uses fundamental cycles in the expansion process and has the time and space complexity of O(n^6) and O(n^2), respectively. To the best of our knowledge, this problem was neither defined nor addressed in the literature. The diameter cycle problem distinguishes itself from other cycle finding problems by identifying cycles that are maximally long while maximizing the distances between vertices in the cycle. Existing cycle finding algorithms such as fundamental and longest cycle algorithms do not discover cycles where the distances between vertices are maximized while also maximizing the length of the cycle

Scalable Column Generation Models and Algorithms for Optical Network Planning Problems

Column Generation Method has been proved to be a powerful tool to model and solve large scale optimization problems in various practical domains such as operation management, logistics and computer design. Such a decomposition approach has been also applied in telecommunication for several classes of classical network design and planning problems with a great success. In this thesis, we confirm that Column Generation Methodology is also a powerful tool in solving several contemporary network design problems that come from a rising worldwide demand of heavy traffic (100Gbps, 400Gbps, and 1Tbps) with emphasis on cost-effective and resilient networks. Such problems are very challenging in terms of complexity as well as solution quality. Research in this thesis attacks four challenging design problems in optical networks: design of p-cycles subject to wavelength continuity, design of dependent and independent p-cycles against multiple failures, design of survivable virtual topologies against multiple failures, design of a multirate optical network architecture. For each design problem, we develop a new mathematical models based on Column Generation Decomposition scheme. Numerical results show that Column Generation methodology is the right choice to deal with hard network design problems since it allows us to efficiently solve large scale network instances which have been puzzles for the current state of art. Additionally, the thesis reveals the great flexibility of Column Generation in formulating design problems that have quite different natures as well as requirements. Obtained results in this thesis show that, firstly, the design of p-cycles should be under a wavelength continuity assumption in order to save the converter cost since the difference between the capacity requirement under wavelength conversion vs. under wavelength continuity is insignificant. Secondly, such results which come from our new general design model for failure dependent p-cycles prove the fact that failure dependent p-cycles save significantly spare capacity than failure independent p-cycles. Thirdly, large instances can be quasi-optimally solved in case of survivable topology designs thanks to our new path-formulation model with online generation of augmenting paths. Lastly, the importance of high capacity devices such as 100Gbps transceiver and the impact of the restriction on number of regeneration sites to the provisioning cost of multirate WDM networks are revealed through our new hierarchical Column Generation model

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

Protection in space division multiplexing elastic optical networks

Orientador: Nelson Luis Saldanha da FonsecaTese (doutorado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: A multiplexação por divisão espacial é uma solução promissora para que as redes ópticas elásticas possam lidar com o esgotamento esperado da capacidade das redes de único núcleo. A introdução da multiplexação por divisão espacial em redes ópticas traz novos desafios para proteção de redes, uma vez que um caminho de luz pode abranger uma alta capacidade e transmitir dados a diferentes taxas. Adicionalmente, a enorme quantidade de tráfego nestas redes provocam a necessidade de proteção contra falhas, uma vez que essas são relativamente frequentes; atualmente, a taxa de falha de um corte de fibra é uma a cada quatro dias. Muitos estudos sobre redes ópticas têm sido desenvolvidos e relatados na literatura. No entanto, apenas recentemente, o estudo de multiplexação espacial para redes ópticas elásticas tem sido considerado. Nesse contexto, embora algoritmos de roteamento e alocação de núcleo e espectro tenham sido propostos na literatura, poucos trabalhos consideram proteção. Além disso, o compartilhamento de recursos de backup não é considerado. Nesta tese, propõe-se soluções de proteção em redes ópticas elásticas com multiplexação espacial, visando a redução do bloqueio de requisições para estabelecimento de conexão, o melhoramento da utilização dos recursos em redes ópticas elásticas com multiplexação espacial, considerando diferentes cenários de carga e topologias. Para tal, o problema de proteção destas redes levará em consideração a utilização de caminhos de proteção, diferentes formatos de modulação, o uso de agregação de tráfego, o uso de sobreposição de espectro em caminhos de proteção, interferência mínima e roteamento multicaminho. Diversos algoritmos foram propostos e avaliados para prover 100% de proteção contra ocorrência de uma falha, bem como um algoritmo para proteção contra duas falhas simultâneas. Os resultados indicam que os algoritmos propostos produzem um melhor desempenho quando comparado ao desempenho dos algoritmos existentes na literaturaAbstract: Spatial division multiplexing is a promising solution proposed for elastic optical networks to cope with the expected depletion of the capacity of single core networks. The introduction of space division multiplexing in optical networks brings new challenges for network protection since a lightpath can span high capacity and transmit data at different rates. In addition, there is the great need for protection mechanisms against failure due to the high volume of traffic carried in these networks. Failure is quite frequent in operational optical networks, it is estimated that there is a failure every four hours. Several studies on optical networks have been carried out but, only recently, the study of spatial division multiplexing for elastic optical networks has been considered. In this context, although routing, spectrum, and core allocation algorithms have been proposed in the literature, only a few papers consider protection. In addition, sharing of backup resources is not considered. In this thesis, it is proposed to provide protection solutions in spatial division multiplexing elastic optical networks, for reducing the blocking of requests for connection establishment, as well as improving the use of resources, considering different load scenarios and topologies. For this, the protection problem of these networks will take into consideration the use of protection paths, different modulation formats, the use of traffic grooming, the use of spectrum overlap in protection paths, minimum interference and multipath routing. Several algorithms are proposed in this thesis to provide 100% protection against a single failure and one algorithm for two simultaneous failure. results indicate that these algorithms overperform existing onesDoutoradoCiência da ComputaçãoDoutor em Ciência da Computação165446/2015-3CNPQCAPE

Fiber Optical Sensing of Bearing Performance and Pump Conditions

Lectur

Survivable Virtual Network Embedding in Transport Networks

Network Virtualization (NV) is perceived as an enabling technology for the future Internet and the 5th Generation (5G) of mobile networks. It is becoming increasingly difficult to keep up with emerging applications’ Quality of Service (QoS) requirements in an ossified Internet. NV addresses the current Internet’s ossification problem by allowing the co-existence of multiple Virtual Networks (VNs), each customized to a specific purpose on the shared Internet. NV also facilitates a new business model, namely, Network-as-a-Service (NaaS), which provides a separation between applications and services, and the networks supporting them. 5G mobile network operators have adopted the NaaS model to partition their physical network resources into multiple VNs (also called network slices) and lease them to service providers. Service providers use the leased VNs to offer customized services satisfying specific QoS requirements without any investment in deploying and managing a physical network infrastructure. The benefits of NV come at additional resource management challenges. A fundamental problem in NV is to efficiently map the virtual nodes and virtual links of a VN to physical nodes and paths, respectively, known as the Virtual Network Embedding (VNE) problem. A VNE that can survive physical resource failures is known as the survivable VNE (SVNE) problem, and has received significant attention recently. In this thesis, we address variants of the SVNE problem with different bandwidth and reliability requirements for transport networks. Specifically, the thesis includes four main contributions. First, a connectivity-aware VNE approach that ensures VN connectivity without bandwidth guarantee in the face of multiple link failures. Second, a joint spare capacity allocation and VNE scheme that provides bandwidth guarantee against link failures by augmenting VNs with necessary spare capacity. Third, a generalized recovery mechanism to re-embed the VNs that are impacted by a physical node failure. Fourth, a reliable VNE scheme with dedicated protection that allows tuning of available bandwidth of a VN during a physical link failure. We show the effectiveness of the proposed SVNE schemes through extensive simulations. We believe that the thesis can set the stage for further research specially in the area of automated failure management for next generation networks