Routing and wavelength assignment vs. wavelength converter placement in all-optical networks

Blocking has been the key performance index in the design of an all-optical network. Existing research demonstrates that an effective routing and wavelength assignment strategy and a proper wavelength converter placement algorithm are the two primary vehicles for improving the blocking performance. However, these two issues have largely been investigated separately in that the existing RWA algorithms have seldom considered the presence of wavelength conversion, while the wavelength converter placement algorithms have largely assumed that a static routing and random wavelength assignment algorithm is employed. The main objective of this article is to present some strong evidences that these two issues need to be considered jointly, and call for the reexamination of both RWA and wavelength converter placement

Modeling and system improvements for wavelength conversion in optical switching nodes

Ph.DDOCTOR OF PHILOSOPH

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

Resilience mechanisms for carrier-grade networks

In recent years, the advent of new Future Internet (FI) applications is creating ever-demanding requirements. These requirements are pushing network carriers for high transport capacity, energy efficiency, as well as high-availability services with low latency. A widespread practice to provide FI services is the adoption of a multi-layer network model consisting in the use of IP/MPLS and optical technologies such as Wavelength Division Multiplexing (WDM). Indeed, optical transport technologies are the foundation supporting the current telecommunication network backbones, because of the high transmission bandwidth achieved in fiber optical networks. Traditional optical networks consist of a fixed 50 GHz grid, resulting in a low Optical Spectrum (OS) utilization, specifically with transmission rates above 100 Gbps. Recently, optical networks have been undergoing significant changes with the purpose of providing a flexible grid that can fully exploit the potential of optical networks. This has led to a new network paradigm termed as Elastic Optical Network (EON). In recent years, the advent of new Future Internet (FI) applications is creating ever-demanding requirements. A widespread practice to provide FI services is the adoption of a multi-layer network model consisting in the use of IP/MPLS and optical technologies such as Wavelength Division Multiplexing (WDM). Traditional optical networks consist of a fixed 50 GHz grid, resulting in a low Optical Spectrum (OS) utilization. Recently, optical networks have been undergoing significant changes with the purpose of providing a flexible grid that can fully exploit the potential of optical networks. This has led to a new network paradigm termed as Elastic Optical Network (EON). Recently, a new protection scheme referred to as Network Coding Protection (NCP) has emerged as an innovative solution to proactively enable protection in an agile and efficient manner by means of throughput improvement techniques such as Network Coding. It is an intuitive reasoning that the throughput advantages of NCP might be magnified by means of the flexible-grid provided by EONs. The goal of this thesis is three-fold. The first, is to study the advantages of NCP schemes in planning scenarios. For this purpose, this thesis focuses on the performance of NCP assuming both a fixed as well as a flexible spectrum grid. However, conversely to planning scenarios, in dynamic scenarios the accuracy of Network State Information (NSI) is crucial since inaccurate NSI might substantially affect the performance of an NCP scheme. The second contribution of this thesis is to study the performance of protection schemes in dynamic scenarios considering inaccurate NSI. For this purpose, this thesis explores prediction techniques in order to mitigate the negative effects of inaccurate NSI. On the other hand, Internet users are continuously demanding new requirements that cannot be supported by the current host-oriented communication model.This communication model is not suitable for future Internet architectures such as the so-called Internet of Things (IoT). Fortunately, there is a new trend in network research referred to as ID/Locator Split Architectures (ILSAs) which is a non-disruptive technique to mitigate the issues related to host-oriented communications. Moreover, a new routing architecture referred to as Path Computation Element (PCE) has emerged with the aim of overcoming the well-known issues of the current routing schemes. Undoubtedly, routing and protection schemes need to be enhanced to fully exploit the advantages provided by new network architectures.In light of this, the third goal of this thesis introduces a novel PCE-like architecture termed as Context-Aware PCE. In a context-aware PCE scenario, the driver of a path computation is not a host/location, as in conventional PCE architectures, rather it is an interest for a service defined within a context.En los últimos años la llegada de nuevas aplicaciones del llamado Internet del Futuro (FI) está creando requerimientos sumamente exigentes. Estos requerimientos están empujando a los proveedores de redes a incrementar sus capacidades de transporte, eficiencia energética, y sus prestaciones de servicios de alta disponibilidad con baja latencia. Es una práctica sumamente extendida para proveer servicios (FI) la adopción de un modelo multi-capa el cual consiste en el uso de tecnologías IP/MPLS así como también ópticas como por ejemplo Wavelength Division Multiplexing (WDM). De hecho, las tecnologías de transporte son el sustento del backbone de las redes de telecomunicaciones actuales debido al gran ancho de banda que proveen las redes de fibra óptica. Las redes ópticas tradicionales consisten en el uso de un espectro fijo de 50 GHz. Esto resulta en una baja utilización del espectro Óptico, específicamente con tasas de transmisiones superiores a 100 Gbps. Recientemente, las redes ópticas están experimentado cambios significativos con el propósito de proveer un espectro flexible que pueda explotar el potencial de las redes ópticas. Esto ha llevado a un nuevo paradigma denominado Redes Ópticas Elásticas (EON). Por otro lado, un nuevo esquema de protección llamado Network Coding Protection (NCP) ha emergido como una solución innovadora para habilitar de manera proactiva protección eficiente y ágil usando técnicas de mejora de throughput como es Network Coding (NC). Es un razonamiento lógico pensar que las ventajas relacionadas con throughput de NCP pueden ser magnificadas mediante el espectro flexible proveído por las redes EONs. El objetivo de esta tesis es triple. El primero es estudiar las ventajas de esquemas NCP en un escenario de planificación. Para este propósito, esta tesis se enfoca en el rendimiento de NCP asumiendo un espectro fijo y un espectro flexible. Sin embargo, contrario a escenarios de planificación, en escenarios dinámicos la precisión relacionada de la Información de Estado de Red (NSI) es crucial, ya que la imprecisión de NSI puede afectar sustancialmente el rendimiento de un esquema NCP. La segunda contribución de esta tesis es el estudio del rendimiento de esquemas de protección en escenarios dinámicos considerando NSI no precisa. Para este propósito, esta tesis explora técnicas predictivas con el propósito de mitigar los efectos negativos de NSI impreciso. Por otro lado, los usuarios de Internet están demandando continuamente nuevos requerimientos los cuales no pueden ser soportados por el modelo de comunicación orientado a hosts. Este modelo de comunicaciones no es factible para arquitecturas FI como es el Internet de las cosas (IoT). Afortunadamente, existe un nueva línea investigativa llamada ID/Locator Split Architectures (ILSAs) la cual es una técnica no disruptiva para mitigar los problemas relacionadas con el modelo de comunicación orientado a hosts. Además, un nuevo esquema de enrutamiento llamado as Path Computation Element (PCE) ha emergido con el propósito de superar los problemas bien conocidos de los esquemas de enrutamiento tradicionales. Indudablemente, los esquemas de enrutamiento y protección deben ser mejorados para que estos puedan explotar las ventajas introducidas por las nuevas arquitecturas de redes. A luz de esto, el tercer objetivo de esta tesis es introducir una nueva arquitectura PCE denominada Context-Aware PCE. En un escenario context-aware PCE, el objetivo de una acción de computación de camino no es un host o localidad, como es el caso en lo esquemas PCE tradicionales. Más bien, es un interés por un servicio definido dentro de una información de contexto