Differentiated quality-of-recovery and quality-of-protection in survivable WDM mesh networks

In the modern telecommunication business, there is a need to provide different Quality-of-Recovery (QoR) and Quality-of-Protection (QoP) classes in order to accommodate as many customers as possible, and to optimize the protection capacity cost. Prevalent protection methods to provide specific QoS related to protection are based on pre-defined shape protection structures (topologies), e.g., p -cycles and p -trees. Although some of these protection patterns are known to provide a good trade-off among the different protection parameters, their shapes can limit their deployment in some specific network conditions, e.g., a constrained link spare capacity budget and traffic distribution. In this thesis, we propose to re-think the design process of protection schemes in survivable WDM networks by adopting a hew design approach where the shapes of the protection structures are decided based on the targeted QoR and QoP guarantees, and not the reverse. We focus on the degree of pre-configuration of the protection topologies, and use fully and partially pre-cross connected p -structures, and dynamically cross connected p -structures. In QoR differentiation, we develop different approaches for pre-configuring the protection capacity in order to strike different balances between the protection cost and the availability requirements in the network; while in the QoP differentiation, we focus on the shaping of the protection structures to provide different grades of protection including single and dual-link failure protection. The new research directions proposed and developed in this thesis are intended to help network operators to effectively support different Quality-of-Recovery and Quality-of-Protection classes. All new ideas have been translated into mathematical models for which we propose practical and efficient design methods in order to optimize the inherent cost to the different designs of protection schemes. Furthermore, we establish a quantitative relation between the degree of pre-configuration of the protection structures and their costs in terms of protection capacity. Our most significant contributions are the design and development of Pre-Configured Protection Structure (p-structure) and Pre-Configured Protection Extended-Tree (p -etree) based schemes. Thanks to the column generation modeling and solution approaches, we propose a new design approach of protection schemes where we deploy just enough protection to provide different quality of recovery and protection classe

p-Cycle Based Protection in WDM Mesh Networks

Abstract p-Cycle Based Protection in WDM Mesh Networks Honghui Li, Ph.D. Concordia University, 2012 WDM techniques enable single fiber to carry huge amount of data. However, optical WDM networks are prone to failures, and therefore survivability is a very important requirement in the design of optical networks. In the context of network survivability, p-cycle based schemes attracted extensive research interests as they well balance the recovery speed and the capacity efficiency. Towards the design of p-cycle based survivableWDM mesh networks, some issues still need to be addressed. The conventional p-cycle design models and solution methods suffers from scalability issues. Besides, most studies on the design of p-cycle based schemes only cope with single link failures without any concern about single node failures. Moreover, loop backs may exist in the recovery paths along p-cycles, which lead to unnecessary stretching of the recovery path lengths. This thesis investigates the scalable and efficient design of segment p-cycles against single link failures. The optimization models and their solutions rely on large-scale optimization techniques, namely, Column Generation (CG) modeling and solution, where segment pcycle candidates are dynamically generated during the optimization process. To ensure full node protection in the context of link p-cycles, we propose an efficient protection scheme, called node p-cycles, and develop a scalable optimization design model. It is shown that, depending on the network topology, node p-cycles sometimes outperform path p-cycles in iii terms of capacity efficiency. Also, an enhanced segment p-cycle scheme is proposed, entitled segment Np-cycles, for full link and node protection. Again, the CG-based optimization models are developed for the design of segment Np-cycles. Two objectives are considered, minimizing the spare capacity usage and minimizing the CAPEX cost. It is shown that segment Np-cycles can ensure full node protection with marginal extra cost in comparison with segment p-cycles for link protection. Segment Np-cycles provide faster recovery speed than path p-cycles although they are slightly more costly than path p-cycles. Furthermore, we propose the shortcut p-cycle scheme, i.e., p-cycles free of loop backs for full node and link protection, in addition to shortcuts in the protection paths. A CG-based optimization model for the design of shortcut p-cycles is formulated as well. It is shown that, for full node protection, shortcut p-cycles have advantages over path p-cycles with respect to capacity efficiency and recovery speed. We have studied a whole sequence of protection schemes from link p-cycles to path p-cycles, and concluded that the best compromise is the segment Np-cycle scheme for full node protection with respect to capacity efficiency and recovery time. Therefore, this thesis offers to network operators several interesting alternatives to path p-cycles in the design of survivable WDM mesh networks against any single link/node failures