Protection through Thrifty Connguration

An eecient, network-ow-theory based model with an algorithm is proposed for connguration of networks. The connguration results in a structure of paths which can survive any single link failure. For each node-pair two link-or node-disjoint paths are obtained: A working one and one used for backup when a failure aaects the direct one. The subject of minimisation is the length of working paths, and the total capacity used for both, working and backup paths. We compare results obtained by three methods: First, the problem has been formulated as an Integer Linear Program (ILP) and solved by CPLEX. Second, a heuristic method called Iterative Capacity Splitting (ICS) has been worked out. Third, a randomised method called Simulated Allocation (SA) proposed by M. Pioro has been implemented. Furthermore, we present simple heuristics for improving the performance of Simulated Allocation. For minimising the total amount of allocated capacity we propose a method referred to as TCA for reducing the capacity allocation, which can be applied to all three methods. The signiicance of the TCA method is that around 40% of the total capacity can be saved! The obtained results can be used for connguration of SDH, ATM, WDM and other networks.