Queueing Models Performance Analysis in Optical Switching Network Nodes

In optical switching networks, queueing models are often used for modeling, analyzing, and evaluating the performance of switching nodes. These models determine the number of optical packets in the switch and how quickly the switch can serve the traffic. This paper examines the numerical performance of optical switching nodes under various queuing models and simulates a modeling system using the OPNET modeler simulation tool. The study estimates the expected average number of optical packets, the probability of packet loss, and the waiting delay time in an optical switch under different loads and wavelength channels.The study estimates the expected average number of optical packets, the probability of packet loss, and the waiting delay time in an optical switch under different loads and wavelength channels.The study estimates the expected average number of optical packets, the probability of packet loss, and the waiting delay time in an optical switch under different loads and wavelength channels

Mecanismes de resolució de contencions per a xarxes de commutació òptica de ràfegues (OBS)

En aquest treball s’avalua, mitjançant simulació, el comportament de diferents mecanismes de resolució de contencions per a les xarxes de commutació òptica de ràfegues (OBS). La primera part del treball consisteix en programar i incorporar al simulador els mòduls que permeten simular les funcions dels diferents mecanismes avaluats: conversió de longitud d’ona (Conv), fibres de retard (FDL) i combinacions dels dos mecanismes anteriors (Conv+FDL i FDL+Conv). A continuació s’avaluen i es comparen els mecanismes de resolució de contencions en termes de retard i probabilitat de pèrdua en dos escenaris diferents: (1) xarxa amb topologia lineal i fonts directament connectades als nodes de la línia i (2) xarxa formada interconnectant el node central de diverses estrelles, els nodes extrems de les quals són les fonts. Els resultats mostren la diferència de comportament de cada mecanisme de resolució de contencions en funció de la topologia i la ubicació de les fonts a la xarxa. En aquest treball es discuteixen els avantatges i inconvenients d’utilitzar cadascun dels mecanismes per separat així com de manera combinada. A més a més, el treball es complementa amb un apartat teòric on s’expliquen les bases de la tecnologia de commutació òptica de ràfegues (OBS) i dos models analítics senzills per als casos de conversió de longitud d’ona i de fibres de retard

Mecanismes de resolució de contencions per a xarxes de commutació òptica de ràfegues (OBS)

En aquest treball s’avalua, mitjançant simulació, el comportament de diferents mecanismes de resolució de contencions per a les xarxes de commutació òptica de ràfegues (OBS). La primera part del treball consisteix en programar i incorporar al simulador els mòduls que permeten simular les funcions dels diferents mecanismes avaluats: conversió de longitud d’ona (Conv), fibres de retard (FDL) i combinacions dels dos mecanismes anteriors (Conv+FDL i FDL+Conv). A continuació s’avaluen i es comparen els mecanismes de resolució de contencions en termes de retard i probabilitat de pèrdua en dos escenaris diferents: (1) xarxa amb topologia lineal i fonts directament connectades als nodes de la línia i (2) xarxa formada interconnectant el node central de diverses estrelles, els nodes extrems de les quals són les fonts. Els resultats mostren la diferència de comportament de cada mecanisme de resolució de contencions en funció de la topologia i la ubicació de les fonts a la xarxa. En aquest treball es discuteixen els avantatges i inconvenients d’utilitzar cadascun dels mecanismes per separat així com de manera combinada. A més a més, el treball es complementa amb un apartat teòric on s’expliquen les bases de la tecnologia de commutació òptica de ràfegues (OBS) i dos models analítics senzills per als casos de conversió de longitud d’ona i de fibres de retard

A Queueing Network Model of an Edge Optical Burst Switching Node

We consider an edge optical burst switching (OBS) node with or without converters, and with no buffering. The OBS node serves a number of users, each connected to the switch over a fiber link that supports multiple wavelengths. Each wavelength is associated with a 3-state Markovian burst arrival process. The arrival process permits short and long bursts to be modeled. We model the edge OBS node as a closed non-product-form queueing network, with multiple heterogeneous classes, and we develop a suite of approximate decomposition algorithms to analyze it. Our approximate algorithms have a good accuracy, and they provide insight into the effect of various system parameters on the performance of the edge OBS node

Traffic and performance evaluation for optical networks. An Investigation into Modelling and Characterisation of Traffic Flows and Performance Analysis and Engineering for Optical Network Architectures.

The convergence of multiservice heterogeneous networks and ever increasing Internet applications, like peer to peer networking and the increased number of users and services, demand a more efficient bandwidth allocation in optical networks. In this context, new architectures and protocols are needed in conjuction with cost effective quantitative methodologies in order to provide an insight into the performance aspects of the next and future generation Internets. This thesis reports an investigation, based on efficient simulation methodologies, in order to assess existing high performance algorithms and to propose new ones. The analysis of the traffic characteristics of an OC-192 link (9953.28 Mbps) is initially conducted, a requirement due to the discovery of self-similar long-range dependent properties in network traffic, and the suitability of the GE distribution for modelling interarrival times of bursty traffic in short time scales is presented. Consequently, using a heuristic approach, the self-similar properties of the GE/G/¿ are being presented, providing a method to generate self-similar traffic that takes into consideration burstiness in small time scales. A description of the state of the art in optical networking providing a deeper insight into the current technologies, protocols and architectures in the field, which creates the motivation for more research into the promising switching technique of ¿Optical Burst Switching¿ (OBS). An investigation into the performance impact of various burst assembly strategies on an OBS edge node¿s mean buffer length is conducted. Realistic traffic characteristics are considered based on the analysis of the OC-192 backbone traffic traces. In addition the effect of burstiness in the small time scales on mean assembly time and burst size distribution is investigated. A new Dynamic OBS Offset Allocation Protocol is devised and favourable comparisons are carried out between the proposed OBS protocol and the Just Enough Time (JET) protocol, in terms of mean queue length, blocking and throughput. Finally the research focuses on simulation methodologies employed throughout the thesis using the Graphics Processing Unit (GPU) on a commercial NVidia GeForce 8800 GTX, which was initially designed for gaming computers. Parallel generators of Optical Bursts are implemented and simulated in ¿Compute Unified Device Architecture¿ (CUDA) and compared with simulations run on general-purpose CPU proving the GPU to be a cost-effective platform which can significantly speed-up calculations in order to make simulations of more complex and demanding networks easier to develop

Analytic modelling and resource dimensioning of optical burst switched networks

The realisation of optical network architectures may hold the key to delivering the enormous bandwidth demands of next generation Internet applications and services. Optical Burst Switching (OBS) is a potentially cost-effective switching technique that can satisfy these demands by offering a high bit rate transport service that is bandwidth-efficient under dynamic Internet traffic loads. Although various aspects of OBS performance have been extensively investigated, there remains a need to systematically assess the cost/performance trade-offs involved in dimensioning OBS switch resources in a network. This goal is essential in enabling the future deployment of OBS but poses a significant challenge due to the complexity of obtaining tractable mathematical models applicable to OBS network optimisation. The overall aim of this thesis lies within this challenge. This thesis firstly develops a novel analytic performance model of an OBS node where burst contention is resolved by combined use of Tuneable Wavelength Converters (TWCs) and Fibre Delay Lines (FDLs) connected in an efficient share-per-node configuration. The model uses a two-moment traffic representation that gives a good trade-off between accuracy and complexity, and is suitable for extension to use in network modelling. The OBS node model is then used to derive an approximate analytic model of an OBS network of switches equipped with TWCs and FDLs, again maintaining a two-moment traffic model for each end-to-end traffic path in the network. This allows evaluation of link/route loss rates under different offered traffic characteristics, whereas most OBS network models assume only a single-moment traffic representation. In the last part of this thesis, resource dimensioning of OBS networks is performed by solving single and multi-objective optimisation problems based on the analytic network model. The optimisation objectives relate to equipment cost minimisation and throughput maximisation under end-to-end loss rate constraints. Due to non-convexity of the network performance constraint equations, a search heuristic approach has been taken using a constraint-handling genetic algorithm