Network Control and Management Challenges in Opaque Networks Utilizing Transparent Optical Switches

This article considers both opaque networks --- OEO conversions occur in the signal path at either the WDM systems if transponders (that incorporate a transmitter and receiver) are present or the switches if transceivers are present --- and transparent networks (no OEO conversions in the signal path). It addresses and clarifies some fundamental issues surrounding all-optical networking and switching, and analyzes the trade-offs between transparent and opaque networking, and between transparent and opaque switching in opaque networks. To carry out our assessment of opaque and transparent networks, we make the following basic assumptions on the requirements for core mesh networks: .Network operators require a lowest-cost network, not just lowest-cost network elements. For example, even though optical may be cheaper than electrical network elements, a network without wavelength conversion and tunable wavelength access in the optical domain could lead to higher network cost due to inefficient capacity usage than a network with wavelength conversion in the electrical domai

Performance analysis of a proposed hybrid optical network

This dissertation discusses a novel Hybrid Optical Network (HON) that can provide service differentiation based on traffic characteristics (i.e., packet, burst, and long-lived flow) with QoS guarantee not only in network layer, but also in physical layer. The DHON consists of sophisticated edge-nodes, which can classify, monitor, and dynamically adjust optical channels in the core layer as traffic variation. The edge nodes aggregate traffic, identifying end-to-end delay by ingress queuing delay or burst timeout. The network can estimate number of channels by arriving traffic intensity and distribution with estimated upper-bound delay. The core layer employs two parallel optical switches (OCS, OBS) in the same platform. Thanks to the overflow system, the proposed network enhances utilization with fewer long distance premium channels. The premium channel can quickly handle burst traffic without new channel assignment. With less overprovisioning capacity design, the premium channel enhances utilization and decrease number of costly premium channels. This research also proposes mathematic models to represent particular DHON channels (i.e., circuit, packet, and burst). We employ method of moments based on overflow theory to forecast irregular traffic pattern from circuit-based channel (i.e., M/M/c/c) to overflow channel, in which G/G/1 model based on Ph/Ph/1 matrix can represent the overflow channel. Moreover, secondary channel supports packet-based traffic over wavelength channel with two service classes: Class I based on delay sensitive traffic (i.e., long flow) and Class II for non-delay sensitive traffic (e.g., best effort). In addition, mixture of traffic in the wavelength channels is investigated based on M/G/1 and M/G/2 with specific service time distribution for particular class. Finally, we show our DHON based on (O-O-O) switching paradigm has improved the performance over typical (O-E-O) switching network architecture based on NSF topology

Dimensionamento de redes ópticas multicamada

Doutoramento em Engenharia ElectrónicaEste trabalho apresenta um estudo sobre o dimensionamento de redes ópticas, com vistas a obter um modelo de dimensionamento para redes de transporte sobreviventes. No estudo utilizou-se uma abordagem estatística em detrimento à determinística. Inicialmente, apresentam-se as principais tecnologias e diferentes arquitecturas utilizadas nas redes ópticas de transporte. Bem como os principais esquemas de sobrevivência e modos de transporte. São identificadas variáveis necessárias e apresenta-se um modelo dimensionamento para redes de transporte, tendo-se dado ênfase às redes com topologia em malha e considerando os modos de transporte opaco, transparente e translúcido. É feita uma análise rigorosa das características das topologias de redes de transporte reais, e desenvolve-se um gerador de topologias de redes de transporte, para testar a validade dos modelos desenvolvidos. Também é implementado um algoritmo genético para a obtenção de uma topologia optimizada para um dado tráfego. São propostas expressões para o cálculo de variáveis não determinísticas, nomeadamente, para o número médio de saltos de um pedido, coeficiente de protecção e coeficiente de restauro. Para as duas últimas, também é analisado o impacto do modelo de tráfego. Verifica-se que os resultados obtidos pelas expressões propostas são similares às obtidas por cálculo numérico, e que o modelo de tráfego não influencia significativamente os valores obtidos para os coeficientes. Finalmente, é demonstrado que o modelo proposto é útil para o dimensionamento e cálculo dos custos de capital de redes com informação incompleta.This work presents a study on the dimensioning of optical networks, aiming to obtain a dimensioning model for survivable optical transport networks. The study relies on a statistical approach rather than a deterministic approach. Initially, enabling technologies and different architectures usually employed in optical transport networks are presented. The main survivability schemes and transport modes are also presented. Useful variables are identified and a transport network dimensioning model is presented, with emphasis on mesh-based network topologies, and considering opaque, transparent and translucent transport modes. A rigorous analysis on the characteristics of real-world transport networks is done, and a topology generator is developed. The topology generator is used for testing and validating the developed models. A genetic algorithm for obtaining an optimized topology for a given traffic load is implemented as well. Expressions for calculating non-deterministic variables are proposed, namely for the average number of hops per demand, protection and restoration coefficient. For the last two, the impact of the traffic model was analyzed. It is shown that results obtained from the proposed expressions are quite similar to the ones obtained from numeric calculation. Moreover, the traffic model does not influence significantly the values obtained for the coefficients. Finally, it is shown that the proposed model is useful for the dimensioning and calculation of capital expenditures of networks in absence of complete information.FCT - SFRH/BD/27545/200