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Lightpath Management of Logical Topology with Incremental Traffic Changes for Reliable IP over WDM Networks

In order to construct a reliable IP over WDM network, backup paths as well as primary paths should be embedded within a wavelength-routed topology (or logical topology). There are many researches treating a design problem of such logical topologoies. However, most of existing approaches assume that the traffic demand is known a priori. In this paper, we propose a new approach, called an incremental capacity dimensioning approach, to design the logical topology. Our incremental approach consists of three steps for building the logical topology: an initial phase, an incremental phase, and a readjustment phase. By our approach, the logical topology can be adjusted according to the incrementally changing traffic demand. During the incremental phase, the primary path is added according to the traffic increase. At that time, the backup lightpaths are reconfigured since those do not affect the carried traffic on the operating primary paths. Our proposed algorithm, called MRB (Minimum Reconfiguring for Backup lightpath), assigns the wavelength route in such a way that the number of backup lightpaths to be reconfigured is minimized. Our results show that the total traffic volume which the IP over WDM network can accommodate is improved by using our MRB algorithm. Then, under the condition that the traffic load within the operating network is appropriately measured, the existing approach for designing the logical toplogy can be applied in the reconfiguration phase. In this paper, we also introduce a notion of “Quality of Protection (QoP).” It descriminates the wavelength routes according to the quality level of those routes, which is a realization of “QoS (Quality of Service)” suitable to IP over WDM networks. For this purpose, we extend our proposal and formulate the design problem in order to treat QoP.