A sequential iterative methodology is used to generate a solution space with different cost/availability values for multiple network architectures from which an optimal or near-optimal solution can be determined. A modeling module (10) provides a cost value for a network architecture under consideration and, once cost modeling is done, an availability analysis is performed for the architecture under analysis. If a relatively few connections prevent a model from acceptability, the availability analysis module (12) reveals the causing factors of the unsatisfactory availability for those few connections and suggests that the modeling perform further optimisations on those causing factors. This iterative process is repeated until an optimum or near-optimum acceptable solution is found; if no acceptable solution is found, the solutions generated in the availability analysis module are reviewed to find the best available solution.