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

Crosstalk aware light-path selection in optical wdm/dwdm networks

Physical layer impairments are the major limitation for the high speed optical WDM/DWDM networks. They significantly affect the signal quality resulting poor quality of transmission which is normally expressed in terms of bit-error rate. To cope of with the future demand, increase in the no of channels and data speed further enhances these impairments. Hence new techniques are needed, which mitigate these impairments and ensure a better quality of transmission. Among the physical layer impairments we have studied the impact of in-band crosstalk on transmission performance of a transparent WDM/DWDM network. Error probabilities and power penalties produced by crosstalk are also investigated. As traditional RWA scheme pays a little regard to the physical layer impairments and cannot provide optimized network performance in practical networks, we have proposed a novel BER constrained, FWM aware RWA algorithm. The performance of the proposed algorithm is demonstrated through simulation and the results show that our algorithm not only gives a guaranteed quality of transmission but also improves the network performance in terms of blocking probability

Wavelengths switching and allocation algorithms in multicast technology using m-arity tree networks topology

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University London.In this thesis, the m-arity tree networks have been investigated to derive equations for their nodes, links and required wavelengths. The relationship among all parameters such as leaves nodes, destinations, paths and wavelengths has been found. Three situations have been explored, firstly when just one server and the leaves nodes are destinations, secondly when just one server and all other nodes are destinations, thirdly when all nodes are sources and destinations in the same time. The investigation has included binary, ternary, quaternary and finalized by general equations for all m-arity tree networks. Moreover, a multicast technology is analysed in this thesis to transmit data carried by specific wavelengths to several clients. Wavelengths multicast switching is well examined to propose split-convert-split-convert (S-C-S-C) multicast switch which consists of light splitters and wavelengths converters. It has reduced group delay by 13% and 29% compared with split-convert (S-C) and split-convert-split (S-C-S) multicast switches respectively. The proposed switch has also increased the received signal power by a significant value which reaches 28% and 26.92% compared with S-C-S and S-C respectively. In addition, wavelengths allocation algorithms in multicast technology are proposed in this thesis using tree networks topology. Distributed scheme is adopted by placing wavelength assignment controller in all parents’ nodes. Two distributed algorithms proposed shortest wavelength assignment (SWA) and highest number of destinations with shortest wavelength assignment (HND-SWA) algorithms to increase the received signal power, decrease group delay and reduce dispersion. The performance of the SWA algorithm was almost better or same as HND-SWA related to the power, dispersion and group delay but they are always better than other two algorithms. The required numbers of wavelengths and their utilised converters have been examined and calculated for the researched algorithms. The HND-SWA has recorded the superior performance compared with other algorithms. It has reduced number of utilised wavelengths up to about 19% and minimized number of the used wavelengths converters up to about 29%. Finally, the centralised scheme is discussed and researched and proposed a centralised highest number of destinations (CHND) algorithm with static and dynamic scenarios to reduce network capacity decreasing (Cd) after each wavelengths allocation. The CDHND has reduced (Cd) by about 16.7% compared with the other algorithms

Dynamic Provisioning of Fault Tolerant Optical Networks for Data Centers

Survivability of files in data centers, when a disaster occurs, is becoming a major challenge in designing cloud-based services. When such a disaster occurs, a specific geographical area is affected and components of communication networks (e.g., nodes and fibers) within the affected area become faulty, leading to the failure of one or more on-going communication. To handle such a situation, a robust communication protocol is needed, so that provisions can be made to allocate an alternative fault-free path, when a disaster disrupts the path used for data communication before the disaster occurs. In this work we have presented a new approach to this problem, in the case of dynamic Route and Wavelength Assignment (RWA) in WDM networks. In our approach, a communication request can be handled only if it is possible to set up i) a primary lightpath that minimizes the number of disasters that may affect the lightpath and ii) (for each disaster that disrupts the primary lightpath), a backup lightpath that avoids the disaster. We have proposed, implemented and studied an efficient heuristic to solve this problem