Multicasting and broadcasting in large WDM networks

The issue of multicasting and broadcasting in wide area wavelength division multiplexing (WDM) networks in which a source broadcasts a message to all members in S (⊂V) is addressed. The optimal multicast tree problem is formalized. Given a directed network G = (V, E) with a given source s and a set S of nodes, |V| = n and |E| = m. Associated with every link e∈E, there is a set Λ(e) of available wavelengths on it. Assume that every node in S is reachable from s, the problem is to find a multicast tree rooted at s including all nodes and the cost of using wavelengths conversion at nodes and the cost of using wavelengths on links