SRG-disjoint design with dedicated and shared protection

We consider a one layer network design problem in the presence of Shared Risk Groups (SRGs).We can define an SRG as a set of links of the logical layer that simultaneously fail in the case of a failure of a lower layer.We propose a mathematical model for the dedicated protection and two alternative models for the shared protection, all based on flow variables. In addition we propose a simple constructive heuristic.We report some computational results that compare the outcome of the models (upper and lower bounds provided by a commercial software) and those of the heuristic.