Towards faster techno-economic evaluation of network scenarios via a modular network equipment database

Techno-economic analysis is used to evaluate technological solutions in different business environments via a simulation based approach. Four steps can be observed in techno-economic analysis: scope definition, modeling of costs and revenues, evaluation of the different solutions and refinement of the analysis. During the scoping step, the boundaries of the analysis are determined, the problem is divided into sub problems and a list of input values is collected. The collection of complete and precise inputs is of the greatest importance as faulty data leads to unreliable results (garbage in garbage out). Today, due to the lack of a structured way of sharing input values, inputs need to be collected on a case-by-case basis. Although a valid approach, it remains a time intensive process prone to errors. This paper therefore proposes a modular network equipment database containing a set of generic equipment such as an IP/MPLS router, a DWDM node, a fiber link and a twisted pair cable. Each of these is represented as a modular block model and described by a set of attributes and a set of drivers which are used to chain one network equipment's block model to one or more others. A complex network can as such be modeled as a chain of equipment block models which are determined by a set of drivers. As a consequence, the collection of inputs can be fast tracked, the problem of missing inputs can be partially resolved and cross-case comparison becomes possible. To make things more concrete, we illustrate this approach via the evaluation of a network scenario in which a network service provider expands its network with an extra core location

Genetic algorithm for the topological design of survivable optical transport networks

We develop a genetic algorithm for the topological design of survivable optical transport networks with minimum capital expenditure. Using the developed genetic algorithm we can obtain near-optimal topologies in a short time. The quality of the obtained solutions is assessed using an integer linear programming model. Two initial population generators, two selection methods, two crossover operators, and two population sizes are analyzed. Computational results obtained using real telecommunications networks show that by using an initial population that resembles real optical transport networks a good convergence is achieved

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

Generating realistic optical transport network topologies

We address the problem of generating physical realistic optical transport network topologies. This type of network has characteristics that differ from scale-free networks, such as the Internet. Based on the analysis of a set of real transport topologies, we identify and assess relevant characteristics. Amethod to generate realistic topologies is proposed. The proposed method is validated by comparing the characteristics of computer-generated and real-world optical transport networks

Análise estatística e modelação de redes óticas de transporte

Doutoramento em TelecomunicaçõesStatistical analysis and modeling of networks is now an integral part of network science and engineering. In case of optical transport networks (OTNs), it can be used for the planning and dimensioning when the complete information is not available or is difficult to process. The core networks around the world today are almost optical and they form the backbone of the Internet. Therefore, the statistical characteristics of these networks must be studied to understand their nature and to estimate their parameters. In science and technology, network analysis and modeling are used for several purposes such as the analysis of their stability, reliability and long term evolution. Knowledge of the statistical models helps in the estimation of several critical parameters of the networks. The work presented in this thesis is focused on the analysis and modeling of link lengths and shortest path lengths in OTNs. The parameters used in the models presented in this thesis can be estimated from the very basic information of the networks such as the coverage area and the number of nodes, both of which can be found from the node locations. These models can be applied to estimate key parameters of the networks. In this thesis, we have shown that the link lengths of the OTNs follow general extreme value distribution. The parameters of the proposed distribution can be estimated from the average link lengths of the networks. We develop expressions for the average link lengths of OTNs which can be estimated with an average error of just 11%. We apply the developed model to estimate link length dependent parameters in OTNs. We show that the shortest path lengths of the OTNs follow Johnson SB distribution. We estimate the parameters of the developed model from the convex area and the number of nodes of the network. We also apply this model to estimate several shortest path-dependent parameters in OTNs.A análise estatística e modelação de redes é atualmente uma parte integrante da ciência e engenharia de redes. No caso das redes óticas de transporte (OTN), a modelação estatistica pode ser usada para o planeamento e dimensionamento quando a informação completa não está disponível ou o seu processamento é muito demorado. As redes óticas constituem atualmente o núcleo central das redes que suportam a Internet. Portanto, as características estatísticas dessas redes devem ser estudadas por forma a compreender sua natureza e estimar os seus parâmetros. Em ciência e tecnologia, a análise e modelação de redes é usada para vários fins, tais como análise de estabilidade, fiabilidade e evolução a longo prazo. O conhecimento dos modelos estatísticos ajuda na estimativa de vários parâmetros críticos das redes. O trabalho apresentado nesta tese está focado na análise e modelação dos comprimentos das ligaçães e dos caminhos mais curtos em OTN. Os parâmetros usados nos modelos apresentados nesta tese podem ser estimados a partir de informação muito simples das redes, tais como a sua área de cobertura e o número de nós, sendo que ambas podem ser obtidas a partir da localização dos nós. Estes modelos podem ser aplicados para estimar parâmetros-chave das redes. Nesta tese, demonstramos que o comprimento dos ligações em OTN segue uma distribuição do tipo general extreme value. Os parâmetros da distribuição podem ser estimados a partir do comprimento médio das ligações. Por sua vez mostramos que o comprimento médio das ligações pode ser estimado com um erro médio de 11% sendo apenas conhecida a área de cobertura da rede. Mostramos como é possivel aplicar o modelo desenvolvido à estimação de parâmetros dependentes do comprimento das ligações. Mostramos também que o comprimento dos caminhos mais curtos segue uma distribuição do tipo Johnson SB. Os parâmetros usados neste modelo podem ser estimados a partir da área convexa e do número de nós da rede. Aplicamos ainda este modelo para estimar diversos parâmetros dependentes do caminho mais curto

Using GRASP and GA to design resilient and cost-effective IP/MPLS networks

The main objective of this thesis is to find good quality solutions for representative instances of the problem of designing a resilient and low cost IP/MPLS network, to be deployed over an existing optical transport network. This research is motivated by two complementary real-world application cases, which comprise the most important commercial and academic networks of Uruguay. To achieve this goal, we performed an exhaustive analysis of existing models and technologies. From all of them we took elements that were contrasted with the particular requirements of our counterparts. We highlight among these requirements, the need of getting solutions transparently implementable over a heterogeneous network environment, which limit us to use widely standardized features of related technologies. We decided to create new models more suitable to fit these needs. These models are intrinsically hard to solve (NP-Hard). Thus we developed metaheuristic based algorithms to find solutions to these real-world instances. Evolutionary Algorithms and Greedy Randomized Adaptive Search Procedures obtained the best results. As it usually happens, real-world planning problems are surrounded by uncertainty. Therefore, we have worked closely with our counterparts to reduce the fuzziness upon data to a set of representative cases. They were combined with different strategies of design to get to scenarios, which were translated into instances of these problems. Finally, the algorithms were fed with this information, and from their outcome we derived our results and conclusions

GMPLS-OBS interoperability and routing acalability in internet

The popularization of Internet has turned the telecom world upside down over the last two decades. Network operators, vendors and service providers are being challenged to adapt themselves to Internet requirements in a way to properly serve the huge number of demanding users (residential and business). The Internet (data-oriented network) is supported by an IP packet-switched architecture on top of a circuit-switched, optical-based architecture (voice-oriented network), which results in a complex and rather costly infrastructure to the transport of IP traffic (the dominant traffic nowadays). In such a way, a simple and IP-adapted network architecture is desired. From the transport network perspective, both Generalized Multi-Protocol Label Switching (GMPLS) and Optical Burst Switching (OBS) technologies are part of the set of solutions to progress towards an IP-over-WDM architecture, providing intelligence in the control and management of resources (i.e. GMPLS) as well as a good network resource access and usage (i.e. OBS). The GMPLS framework is the key enabler to orchestrate a unified optical network control and thus reduce network operational expenses (OPEX), while increasing operator's revenues. Simultaneously, the OBS technology is one of the well positioned switching technologies to realize the envisioned IP-over-WDM network architecture, leveraging on the statistical multiplexing of data plane resources to enable sub-wavelength in optical networks. Despite of the GMPLS principle of unified control, little effort has been put on extending it to incorporate the OBS technology and many open questions still remain. From the IP network perspective, the Internet is facing scalability issues as enormous quantities of service instances and devices must be managed. Nowadays, it is believed that the current Internet features and mechanisms cannot cope with the size and dynamics of the Future Internet. Compact Routing is one of the main breakthrough paradigms on the design of a routing system scalable with the Future Internet requirements. It intends to address the fundamental limits of current stretch-1 shortest-path routing in terms of RT scalability (aiming at sub-linear growth). Although "static" compact routing works fine, scaling logarithmically on the number of nodes even in scale-free graphs such as Internet, it does not handle dynamic graphs. Moreover, as multimedia content/services proliferate, the multicast is again under the spotlight as bandwidth efficiency and low RT sizes are desired. However, it makes the problem even worse as more routing entries should be maintained. In a nutshell, the main objective of this thesis in to contribute with fully detailed solutions dealing both with i) GMPLS-OBS control interoperability (Part I), fostering unified control over multiple switching domains and reduce redundancy in IP transport. The proposed solution overcomes every interoperability technology-specific issue as well as it offers (absolute) QoS guarantees overcoming OBS performance issues by making use of the GMPLS traffic-engineering (TE) features. Keys extensions to the GMPLS protocol standards are equally approached; and ii) new compact routing scheme for multicast scenarios, in order to overcome the Future Internet inter-domain routing system scalability problem (Part II). In such a way, the first known name-independent (i.e. topology unaware) compact multicast routing algorithm is proposed. On the other hand, the AnyTraffic Labeled concept is also introduced saving on forwarding entries by sharing a single forwarding entry to unicast and multicast traffic type. Exhaustive simulation campaigns are run in both cases in order to assess the reliability and feasible of the proposals