p-Cycle Based Protection in WDM Mesh Networks

摘要

Abstractudp-Cycle Based Protection in WDM Mesh NetworksudHonghui Li, Ph.D.udConcordia University, 2012udWDM techniques enable single fiber to carry huge amount of data. However, optical WDMudnetworks are prone to failures, and therefore survivability is a very important requirementudin the design of optical networks. In the context of network survivability, p-cycle basedudschemes attracted extensive research interests as they well balance the recovery speed andudthe capacity efficiency. Towards the design of p-cycle based survivableWDM mesh networks,udsome issues still need to be addressed. The conventional p-cycle design models and solutionudmethods suffers from scalability issues. Besides, most studies on the design of p-cycleudbased schemes only cope with single link failures without any concern about single nodeudfailures. Moreover, loop backs may exist in the recovery paths along p-cycles, which leadudto unnecessary stretching of the recovery path lengths.udThis thesis investigates the scalable and efficient design of segment p-cycles against singleudlink failures. The optimization models and their solutions rely on large-scale optimizationudtechniques, namely, Column Generation (CG) modeling and solution, where segment pcycleudcandidates are dynamically generated during the optimization process. To ensure fulludnode protection in the context of link p-cycles, we propose an efficient protection scheme,udcalled node p-cycles, and develop a scalable optimization design model. It is shown that,uddepending on the network topology, node p-cycles sometimes outperform path p-cycles inudiiiudterms of capacity efficiency. Also, an enhanced segment p-cycle scheme is proposed, entitledudsegment Np-cycles, for full link and node protection. Again, the CG-based optimizationudmodels are developed for the design of segment Np-cycles. Two objectives are considered,udminimizing the spare capacity usage and minimizing the CAPEX cost. It is shown thatudsegment Np-cycles can ensure full node protection with marginal extra cost in comparisonudwith segment p-cycles for link protection. Segment Np-cycles provide faster recovery speedudthan path p-cycles although they are slightly more costly than path p-cycles. Furthermore,udwe propose the shortcut p-cycle scheme, i.e., p-cycles free of loop backs for full node andudlink protection, in addition to shortcuts in the protection paths. A CG-based optimizationudmodel for the design of shortcut p-cycles is formulated as well. It is shown that, for full nodeudprotection, shortcut p-cycles have advantages over path p-cycles with respect to capacityudefficiency and recovery speed. We have studied a whole sequence of protection schemesudfrom link p-cycles to path p-cycles, and concluded that the best compromise is the segmentudNp-cycle scheme for full node protection with respect to capacity efficiency and recoveryudtime. Therefore, this thesis offers to network operators several interesting alternatives toudpath p-cycles in the design of survivable WDM mesh networks against any single link/nodeudfailures.