Optimal multicast in DWDM networks: minimizing wavelength conversion

The problem of assigning wavelengths and routing multicast sessions in DWDM networks has given rise to a host of heuristic and approximate techniques. In this paper we demonstrate that it is feasible to find optimal solutions for many instances of this problem using integer linear programming. The technique presented is also useful as an optimal standard to which heuristics can be compared in order to determine the quality of solutions they generate. The goal of this paper is to document an integer programming tableau for routing multicast sessions in DWDM networks, while accounting for a variety of limits on the abilities of the nodes in the network to drop, split and convert wavelengths. Examples of applying the tableau to problems of moderate size are included.