Energy-efficient traffic engineering

The energy consumption in telecommunication networks is expected to grow considerably, especially in core networks. In this chapter, optimization of energy consumption is approached from two directions. In a first study, multilayer traffic engineering (MLTE) is used to assign energy-efficient paths and logical topology to IP traffic. The relation with traditional capacity optimization is explained, and the MLTE strategy is applied for daily traffic variations. A second study considers the core network below the IP layer, giving a detailed power consumption model. Optical bypass is evaluated as a technique to achieve considerable power savings over per-hop opticalelectronicoptical regeneration. Document type: Part of book or chapter of boo

Traffic engineering in dynamic optical networks

Traffic Engineering (TE) refers to all the techniques a Service Provider employs to improve the efficiency and reliability of network operations. In IP over Optical (IPO) networks, traffic coming from upper layers is carried over the logical topology defined by the set of established lightpaths. Within this framework then, TE techniques allow to optimize the configuration of optical resources with respect to an highly dynamic traffic demand. TE can be performed with two main methods: if the demand is known only in terms of an aggregated traffic matrix, the problem of automatically updating the configuration of an optical network to accommodate traffic changes is called Virtual Topology Reconfiguration (VTR). If instead the traffic demand is known in terms of data-level connection requests with sub-wavelength granularity, arriving dynamically from some source node to any destination node, the problem is called Dynamic Traffic Grooming (DTG). In this dissertation new VTR algorithms for load balancing in optical networks based on Local Search (LS) techniques are presented. The main advantage of using LS is the minimization of network disruption, since the reconfiguration involves only a small part of the network. A comparison between the proposed schemes and the optimal solutions found via an ILP solver shows calculation time savings for comparable results of network congestion. A similar load balancing technique has been applied to alleviate congestion in an MPLS network, based on the efficient rerouting of Label-Switched Paths (LSP) from the most congested links to allow a better usage of network resources. Many algorithms have been developed to deal with DTG in IPO networks, where most of the attention is focused on optimizing the physical resources utilization by considering specific constraints on the optical node architecture, while very few attention has been put so far on the Quality of Service (QoS) guarantees for the carried traffic. In this thesis a novel Traffic Engineering scheme is proposed to guarantee QoS from both the viewpoint of service differentiation and transmission quality. Another contribution in this thesis is a formal framework for the definition of dynamic grooming policies in IPO networks. The framework is then specialized for an overlay architecture, where the control plane of the IP and optical level are separated, and no information is shared between the two. A family of grooming policies based on constraints on the number of hops and on the bandwidth sharing degree at the IP level is defined, and its performance analyzed in both regular and irregular topologies. While most of the literature on DTG problem implicitly considers the grooming of low-speed connections onto optical channels using a TDM approach, the proposed grooming policies are evaluated here by considering a realistic traffic model which consider a Dynamic Statistical Multiplexing (DSM) approach, i.e. a single wavelength channel is shared between multiple IP elastic traffic flows

Desenvolvimento de heurísticas para o dimensionamento de redes óticas transparentes

In this dissertation a set of heuristic algorithms was developed, implemented and validated for the dimensioning of transparent optical networks. A generic platform was also created in order to allow the heuristics development and implementation, based on two main entities: a logical layer manager and a physical layer manager. The referred structure was designed in order to allow the test of a vast variety of heuristic algorithms. Within the scope of this dissertation were developed traffic scheduling algorithms based on the individual traffic quantity of each request. In addition, some routing, grooming and wavelength assignment algorithms were also developed. The main goal of these heuristics is is to dimension networks, while recurring to the minimum possible amount of resources, thus minimizing the CAPEX of the network, while also trying to guarantee the total traffic routing. For simplicity reasons only the case of networks without survivabilty was treated, although the platform is sufficiently generic to allow its inclusion in future work. Regarding the economic aspects, a detailed and comparative study was conducted, focusing on the networks CAPEX, in order to validate and assess the quality of the solutions provided by the heuristics developed based on the solutions given by an integer linear programming model. Finally, some conclusions and possible future work are discussed.Nesta dissertação foram desenvolvidas, implementadas e validadas heurísticas para o dimensionamento de redes óticas de transporte transparentes. Foi criada uma plataforma genérica para o desenvolvimento e a implementação das heurísticas baseada em duas entidades principais: um gestor de recursos da camada lógica e um gestor de recursos da camada física. Esta estrutura foi desenhada de modo a poder ser usada para testar uma grande variedade de heurísticas. No âmbito desta tese foram desenvolvidas heuristicas considerando o escalonamento dos pedidos baseados na quantidade de tráfego de cada pedido. Foram ainda desenvolvidos algoritmos para o encaminhamento, a atribuição de comprimentos de onda e agregação dos pedidos de tráfego. O objetivo das heurísticas passa pelo dimensionamento de uma rede, onde recorrendo-se a um mínimo possível de recursos, e portanto, minimizando o CAPEX da rede, se tenta garantir o encaminhamento total do tráfego. Por uma questão de simplificidade apenas foram consideradas redes sem sobrevivência, no entanto, a plataforma é suficientemente genérica para permitir a inclusão de sobrevivência. Tendo também em conta a referida vertente económica, foi elaborado um estudo detalhado e comparativo, tendo em foco o CAPEX da rede, com o objetivo de validar a qualidade das soluções fornecidas pelas heurísticas desenvolvidas tendo por base os valores obtidos através de um modelo baseado em programação linear inteira. Finalmente, são partilhadas e discutidas algumas conclusões e direções para o desenvolvimento de trabalho futuro.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Design cost and spectrum efficiency comparison of fixed-grid and flex-grid optical networks with grooming

This paper deals with the design of optical networks aiming to minimize the design cost and the spectrum usage. We present an optimization method that is able to find the optimal solutions of relevant sized instances. We apply the method to realistic case studies. With the obtained solutions, we make a cost and spectrum efficiency comparison analysis between fixed-grid and flex-grid optical networks. The results show that flex-grid gains are significant over the fixed-grid alternatives only after the introduction of 400 Gbps line rates and marginal gains are obtained without this line rate

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

Migration strategies toward all optical metropolitan access rings

This paper was published in Journal of Lightwave Technology and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the IEEE website: http://dx.doi.org/10.1109/JLT.2007.901325. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.Nowadays, network operators are steadily deploying optical circuit switching (OCS) equipment in their metropolitan networks in order to cope with traffic increase and, most importantly, in order to reduce capital expenditures and operational expenditures of existing active technologies. On the other hand, optical burst switching (OBS) technology is expected to become mature in the medium term, and it may be used as an alternative to current OCS networks due to its potential advantages in terms of bandwidth allocation granularity. While OBS is being extensively studied in the literature, little attention has been paid in conducting a comparative analysis of OBS versus OCS, especially concerning cost analysis. In this paper, we provide a comparative analysis of OBS versus OCS as an evolutionary technology for all-optical rings in the metropolitan-access network. This paper is specifically targeted toward optimizing the number of optoelectronic receivers and wavelengths with real traffic matrices from the metropolitan rings in Madrid, Spain. Such matrices also include traffic projections of foreseeable broadband services, which are based on a market analysis from the largest operator in Spain. Our findings show that OCS might be more efficient than OBS in the metro-access segment, which is characterized by a highly centralized traffic pattern. However, the more distributed the traffic is, the more efficient the OBS is as well. Consequently, OBS might be better suited to metro-core networks, which show a more distributed and dynamic traffic pattern.The authors would like to thank the e-Photon/ONe+ network of excellenc

Dynamic grooming in IP over WDM networks: A study with realistic traffic based on GANCLES simulation package

Abstract — Dynamic grooming capabilities lies at the hearth of many envisaged scenarios for IP over Optical networks, but studies on its performance are still in their infancy. This work addresses two fundamental aspects of the problem. First of all it presents a novel tool for the study of IP over Optical networks. The tool, freely available on-line, is a network level simulator named GANCLES that includes several innovative features allowing the study of realistic scenarios in IP over Optical networking, making it an ideal tool for Traffic Engineering purposes. GANCLES architecture enables the simulation of dynamic traffic grooming on top of a realistic network model that correctly describes the logical interaction between the optical and the IP layer, i.e., the mutual relationship between routing algorithms and lightpath assignment procedures at the optical layer and routing at th