Distributed Resources Assignment for Optical Burst Switching without Wavelength Conversion (Invited Paper)

The amount of bursty Internet traffic leads to develop new architectures and technologies, such as Optical Burst Switching (OBS), to efficiently satisfy future bandwidth requirements. Burst loss probability is an important quality of service metric for OBS due to its bufferless characteristic, even more critical without wavelengths converters. So, resource assignment is an important issue to solve in OBS networks. In this paper, two distributed resources assignment schemes without wavelength conversion capability are proposed. Whereas the first one is applied at the edge nodes to achieve a loss-free core network, the second is an enhanced routing and wavelength assignment scheme applied at core nodes. Simulation results indicate that the first scheme offers a loss-free solution with blocking probability only at ingress nodes and high traffic load. The second one reduces the network-wide burst loss probability significantly compared with other schemes.Postprint (published version

Light-mesh — a pragmatic optical access network architecture for IP-centric service oriented communication

Contemporary deployments of optical access networks are based on the principles of Passive Optical Networks (PONs). PONs deploy a star topology and dual wavelength for communication between the center and ends of a star. The star topology requires that each end-user be connected to the star splitter (usually a passive coupler). We argue in this paper that while adhering to the requirements of access networks, we are able to provide a better topological solution in terms of the cost-factor and the ability to upgrade to a greater bandwidth. This solution, called a light-mesh, is based on the concept of pragmatic optical packet transport or light-frames results in a unique node architecture, interconnection matrix, and communication protocols. We begin by investigating into the node architecture that is required for a mesh network in the access area. The proposed node architecture has unique benefits in terms of being able to support the intermittent communication in the access area — nodes are not always powered ON, despite which, it is important to maintain mesh connectivity. Hence we propose the use of largely passive components in node architecture design. Passive components in a mesh lead to collisions of packets in the access area, for which we propose a unique collision detection and recovery scheme based on a logical time-overlap method. Collisions make the end-to-end delay uncertain. Analysis of the associated delay is performed. We then propose algorithms to build such a light-mesh network. These algorithms are investigated in terms of network built-out costs and these costs are compared to a PON topology. Cost differences and a performance comparison with PON are presented as part of the numerical analysis.© Elsevie

Control plane routing in photonic networks

The work described in the thesis investigates the features of control plane functionality for routing wavelength paths to serve a set of sub-wavelength demands. The work takes account of routing problems only found in physical network layers, notably analogue transmission impairments. Much work exists on routing connections for dynamic Wavelength-Routed Optical Networks (WRON) and to demonstrate their advantages over static photonic networks. However, the question of how agile the WRON should be has not been addressed quantitatively. A categorization of switching speeds is extended, and compared with the reasons for requiring network agility. The increase of effective network capacity achieved with increased agility is quantified through new simulations. It is demonstrated that this benefit only occurs within a certain window of network fill; achievement of significant gain from a more-agile network may be prevented by the operator’s chosen tolerable blocking probability. The Wavelength Path Sharing (WPS) scheme uses semi-static wavelengths to form unidirectional photonic shared buses, reducing the need for photonic agility. Making WPS more practical, novel improved routing algorithms are proposed and evaluated for both execution time and performance, offering significant benefit in speed at modest cost in efficiency. Photonic viability is the question of whether a path that the control plane can configure will work with an acceptable bit error rate (BER) despite the physical transmission impairments encountered. It is shown that, although there is no single approach that is simple, quick to execute and generally applicable at this time, under stated conditions approximations may be made to achieve a general solution that will be fast enough to enable some applications of agility. The presented algorithms, analysis of optimal network agility and viability assessment approaches can be applied in the analysis and design of future photonic control planes and network architectures