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Abstract
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Transport networks form the backbone of communication networks by cost-efficiently offering huge bandwidth and by guaranteeing a high service quality and availability. These requirements can best be met by using optical communication technologies. Currently, wavelength-switching is the most prominent network technology employing optical fiber communication and wavelength division multiplexing. While for years progress in optical networks has been defined by ever increasing transmission bit-rates, higher flexibility and manageability as well as multi-service and multi-layer integration are equally important criteria today. Accounting for these trends, optical burst switching (OBS) has been proposed as highly dynamic optical network architecture. It offers fine-granular transport of different packet-switched services and applies statistical multiplexing directly in the optical layer. This thesis presents the design, modeling, and evaluation of the optical burst transport network architecture (OBTN). The architecture is motivated by the need for flexible, scalable, and cost-efficient transport in next generation networks. In addition, it is stimulated by the research activities towards highly dynamic optical network infrastructures. OBTN defines a network architecture to transport and switch optical burst data in a core network. The design objectives for the OBTN architecture are (i) an overall high quality of service, (ii) a network design allowing for cost-efficiency and scalability, and (iii) a network evolution perspective based on the current wavelength-switched networks. These objectives are achieved by combining selected concepts, architectures, and strategies of optical burst and optical packet switching as well as of multi-layer traffic engineering. The method of event-driven simulation is used to evaluate OBTN regarding its node and network resource requirements and QoS performance. Chapter 2 introduces the general characteristics, requirements, and trends for next generation transport networks in general and optical networks in particular. It describes architectural constraints and classification criteria for highly dynamic optical network architectures. These criteria are used to characterize the fast optical circuit switching, optical burst switching, and optical packet switching architectures as well as hybrid optical network architectures. Chapter 3 discusses the state of research and technology for optical burst switching. It presents the requirements for key functions in an OBS network and classifies the proposed architectures and mechanisms. Particularly, it addresses contention resolution which is necessary to achieve a high QoS in burst-switched networks. This is supported by Appendix A which analyzes the performance of nodes with fiber delay line buffers. Finally, architectures and realization aspects for burst-switched core nodes are presented to explain their resource and scalability constraints. Chapter 4 motivates and introduces the fundamental concepts of OBTN, namely the dense virtual topology, constrained alternative routing, and shared overflow capacity. These components are analyzed regarding their consequences for the overall node and network architecture. Finally, OBTN is compared qualitatively with optical burst switching and hybrid optical networks. Chapter 5 describes a unified resource model which allows dimensioning and evaluating burst-switched architectures with different virtual topologies. Then, it addresses the simulation methodology, the reference evaluation scenario used in Chapter 6 as well as the metrics for node and network resources and QoS performance. Chapter 6 evaluates OBTN and compares it with the two burst-switched reference architectures OBS and Burst-over-Circuit-Switching (BoCS). OBS uses a sparse virtual topology while BoCS employs a full-mesh virtual topology. The evaluations show that for the same high target QoS, suitable OBTN dimensionings require substantially less resources in burst-switched nodes than OBS and slightly less than BoCS. This improvement comes at the cost of higher resource requirements compared to OBS in the underlying wavelength-switched server layer. However, applying the cost relations for lambda grid networks, in which bandwidth is considered a commodity and client layer resources the major cost driver, OBTN yields an overall cost reduction. Concluding, OBTN is shown to offer an overall high QoS, to effectively reduce the node resources of the burst-switched client layer, and to perform well in a wavelength-switched network context.
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Reference entry
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Gauger, C.M.
Novel Network Architecture for Optical Burst Transport - Communication Networks and Computer Engineering Report No. 92
Dissertation, Universität Stuttgart, EI, 2006
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