Burst switched optical networks supporting legacy and future service types

Focusing on the principles and the paradigm of OBS an overview addressing expectable performance and application issues is presented. Proposals on OBS were published over a decade and the presented techniques spread into many directions. The paper comprises discussions of several challenges that OBS meets, in order to compile the big picture. The OBS principle is presented unrestricted to individual proposals and trends. Merits are openly discussed, considering basic teletraffic theory and common traffic characterisation. A more generic OBS paradigm than usual is impartially discussed and found capable to overcome shortcomings of recent proposals. In conclusion, an OBS that offers different connection types may support most client demands within a sole optical network layer

Loss-free architectures in optical burst switched networks for a reliable and dynamic optical layer

For the last three decades, the optical fiber has been a quite systematic response to dimensioning issues in the Internet. Originally restricted to long haul networks, the optical network has gradually descended the network hierarchy to discard the bottlenecks. In the 90's, metropolitan networks became optical. Today, optical fibers are deployed in access networks and reach the users. In a near future, besides wireless access and local area networks, all networks in the network hierarchy may be made of fibers, in order to support current services (HDTV) and the emergence of new applications (3D-TV newly commercialized in USA). The deployment of such greedy applications will initiate an upward upgrade. The first step may be the Metropolitan Area Networks (MANs), not only because of the traffic growth, but also because of the variety of served applications, each with a specific traffic profile. The current optical layer is of mitigated efficiency, dealing with unforeseen events. The lack of reactivity is mainly due to the slow switching devices: any on-line decision of the optical layer is delayed by the configuration of the. devices. When the optical network has been extended in the MANs, a lot of efforts has been deployed to improve the reactivity of the optical layer. The Optical Circuit Switching paradigm (OCS) has been improved but it ultimately relies on off-line configuration of the optical devices. Optical Burst Switching (OBS) can be viewed as a highly flexible evolution of OCS, that operates five order of magnitude faster. Within this 'architecture, the loss-free guaranty can be abandoned in order to improve the reactivity of the optical layer. Indeed, reliability and reactivity appear as antagonists properties and getting closer to either of them mitigates the other. This thesis aims at proposing a solution to achieve reliable transmission over a dynamic optical layer. Focusing on OBS networks, our objective is to solve the contention issue without mitigating the reactivity. After the consideration of contention avoidance mechanisms with routing constraints similar as in OCS networks, we investigate the reactive solutions that intend to solve the contentions. None of the available contention resolution scheme can ensure the 100% efficiency that leads to loss-free transmission. An attractive solution is the recourse to electrical buffering, but it is notoriously disregarded because (1) it may highly impact the delays and (2) loss can occur due to buffer overflows. The efficiency of translucent architectures thus highly depends on the buffer availability, that can be improved by reducing the time spent in the buffers and the contention rate. We show that traffic grooming can highly reduce the emission delay, and consequently the buffer occupancy. In a first architecture, traffic grooming is enabled by a translucent core node architecture, capable to re-aggregate incoming bursts. The re-aggregation is mandatory to "de-groom" the bursts in the core network (i.e., to demultiplex the content of a burst). On the one hand, the re-aggregation highly reduces the loss probability, but on the other hand, it absorbs the benefits of traffic grooming. Finally, dynamic access to re-aggregation for contention resolution, despite the significant reduction of the contention rate, dramatically impacts the end-to-end delay and the memory requirement. We thus propose a second architecture, called CAROBS, that exploits traffic grooming in the optical domain. This framework is fully dynamic and can be used jointly with our translucent architecture that performs re-aggregation. As the (de)grooming operations do not involve re-aggregation, the translucent module can be restricted to contention resolution. As a result, the volume of data submitted to re-aggregation is drastically reduced and loss-free transmission can be reached with the same reactivity, end-to-end delay and memory requirement as a native OBS networ

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