Resource allocation and scalability in dynamic wavelength-routed optical networks.

This thesis investigates the potential benefits of dynamic operation of wavelength-routed optical networks (WRONs) compared to the static approach. It is widely believed that dynamic operation of WRONs would overcome the inefficiencies of the static allocation in improving resource use. By rapidly allocating resources only when and where required, dynamic networks could potentially provide the same service that static networks but at decreased cost, very attractive to network operators. This hypothesis, however, has not been verified. It is therefore the focus of this thesis to investigate whether dynamic operation of WRONs can save significant number of wavelengths compared to the static approach whilst maintaining acceptable levels of delay and scalability. Firstly, the wavelength-routed optical-burst-switching (WR-OBS) network architecture is selected as the dynamic architecture to be studied, due to its feasibility of implementation and its improved network performance. Then, the wavelength requirements of dynamic WR-OBS are evaluated by means of novel analysis and simulation and compared to that of static networks for uniform and non-uniform traffic demand. It is shown that dynamic WR-OBS saves wavelengths with respect to the static approach only at low loads and especially for sparsely connected networks and that wavelength conversion is a key capability to significantly increase the benefits of dynamic operation. The mean delay introduced by dynamic operation of WR-OBS is then assessed. The results show that the extra delay is not significant as to violate end-to-end limits of time-sensitive applications. Finally, the limiting scalability of WR-OBS as a function of the lightpath allocation algorithm computational complexity is studied. The trade-off between the request processing time and blocking probability is investigated and a new low-blocking and scalable lightpath allocation algorithm which improves the mentioned trade-off is proposed. The presented algorithms and results can be used in the analysis and design of dynamic WRONs

Um estudo simulacional de redes inter-centrais com encaminhamento dinâmico incluindo redes com integração de serviços

A análise ao comportamento de redes inter-centrais, no respeitante ao grau de serviço, pressupõe o desenvolvimento de modelos analíticos ou simulacionais. O comportamento de tais redes é dependente do método de encaminhamento utilizado, sendo esta uma função indispensável nas redes de telecomunicações. Nas últimas décadas tem sido propostos e/ou implementados um grande número de métodos de encaminhamento alternativos dinâmicos, entre outros casos devidos às necessidades de desempenho de redes cada vez maiores e mais complexas e à introdução de novos serviços. Neste trabalho é feita uma recolha e estudo de alguns desses métodos, que têm sofrido grandes alterações/evoluções desde o seu aparecimento oferecendo consideraveis beneficios no desempenho da rede a custos cada vez mais reduzido. Alguns dos métodos de encaminhamento alternativos dinâmicos estudados são implementados para análise através de simulação. Para tal é construido um simulador do comportamento de redes de teletráfego, nomeadamente no respeitante à análise do grau de serviço, para redes de comutação de circuitos com a possibilidade de integração de diferentes classes de serviços. Este simulador é genérico, e independente do método de encaminhamento que se pretenda simular. A implementação dos métodos é em geral baseada na descrição do comportamento dos métodos presentes na literatura, ocasionalmente suplementada de capacidades adicionais e parametrizações para permitir o estudo do desempenho dos métodos com alterações em relação à descrição original, tal como tornar um método, apresentado originalmente para encaminhar tráfego de apenas um tipo de tráfego, capaz de encaminhar simultaneamente várias classes de tráfego. Finalmente é feito um estudo comparativodos vários métodos de encaminhamento implementados, do ponto de vista do desempenho da rede em diferentes situações de carga. Os métodos são estudados no seu comportamento em diferentes redes (apenas um tipo de tráfego ou vários tipos de tráfego simultaneamente – rede com integração de serviços). The analysis of inter-switch networks, regarding Grade of Service, assumes the development of analytic and simulational models. The performance of these networks is dependent on the routing method used, and as such this is an indispensable function of modern telecommunication networks. On the last previous decades a large number of dynamic alternative routing methods have been proposed and/or implemented. This has happened, among other causes, because of the always-bigger performance requirements on bigger and more complex networks, as well as the introduction of new services. This work includes a survey and study of some of those methods, that have been changing and evolving since their inception, offering considerable benefits on the network performance at ever-lower costs. Some of the dynamic alternative routing methods studied are then implemented for simulational analysis. To do so, a real-time teletraffic simulator was built. This simulator focus on Grade of Service analysis on circuit switching networks, which may allow service integration. It’s generic and routing methods independent simulation tool. The methods are usually implemented according to the behaviour described in the literature, but sometimes, additional capabilities and parameterisations are considered and proposed. This is made to allow the study of the methods performance with some changes to their original formulation. This is also made to allow some methods, originally developed to route a single traffic class, to take into consideration several traffic classes on their routing algorithm. Finally, a comparative study of the implemented routing methods is made, regarding the network performance when subject to different loads. The methods performances are analysed on different networks (both with a single traffic class, and with multiple simultaneous traffic classes – integrated services network)