Traffic Grooming Optimization in Mesh Wdm Networks without Wavelength Converter

This is a tutorial paper on the traffic grooming optimization in mesh Wavelength Division Multiplexing (WDM) networks for static traffic patterns. The traffic grooming technique provides a two-layer traffic engineering capability by aggregating and routing low-bandwidth traffic flows from the upper layer over re-configurable highbandwidth connections in the lower layer. This paper demonstrates how to use the Lagrangian Relaxation and Subgradient Methods (LRSM) to solve the optimization problem over a mesh WDM network where no wavelength converters are used, i.e., a lightpath must use the same wavelength from its source to destination. The framework makes use of a constrained Integer Linear Programming (ILP) formulation. The outputs of our optimization include the selection of profitable traffic flows, the routing schemes for the selected traffic flows over lightpaths, the selection of lightpaths, and the Routing and Wavelength Assignment (RWA) schemes for the selected lightpaths. Some interesting observations are noted.