A network is represented using a graph. The graph comprises a plurality of vertices and a plurality of edges. The vertices comprise a source vertex, a destination vertex and a vertex u. The edges link corresponding adjacent pairs of the vertices. A minimum cost path in the graph is determined from the source vertex to the destination vertex, wherein the vertex u is in the minimum cost path. An edge from the vertex u in the minimum cost path introduces an additional capital expenditure cost that is dependent on how the minimum cost path traverses from the source vertex to the vertex u.