Global versus essential post-disaster re-provisioning in telecom mesh networks

Telecommunication networks face large-scale threats, such as natural disasters (earthquake, hurricane, tsunami, etc.) and targeted attacks (weapons of mass destruction). These disasters may simultaneously destroy many network components (nodes and/or links) and cause multi-failure events. Although existing protection schemes can handle some given multi-failure scenarios, it is extremely challenging to solve all possible disaster-failure scenarios with reasonable resource costs and a 100% reliability guarantee. In this paper, we investigate postdisaster restoration strategies for telecom backbone mesh networks (such as wavelength-division multiplexed networks), whose objective is two-fold: to maintain network connectivity (i.e., guarantee a minimal degree of service for the survived connections) and to maximize the traffic flow in the post-disaster network. We study three postdisaster re-provisioning schemes employing different policies for connection rerouting and admissible bandwidth degradation (i.e., provisioning partial bandwidth). These schemes, whose services range from essential to global post-disaster re-provisioning, are the no-degradation reprovisioning (NDR) scheme, the degradation-as-needed re-provisioning (DAN) scheme, and the fairness-aware degradation re-provisioning (FAD) scheme. Corresponding mixed integer linear program models are developed and applied on two representative mesh topologies. Numerical results show that NDR can effectively decrease the connection loss ratio by rerouting some survived connections. However, both DAN and FAD can achieve optimal performance on maintaining connectivity even without rerouting any survived connections. DAN outperforms the other schemes in terms of traffic loss ratio, but it may cause a large difference between the maximum and minimum degradation ratios. FAD can improve the performance in terms of traffic loss ratio by rerouting a few survived connections. In particular, compared with DAN, FAD can provide balanced bandwidth degradation for all connections by sacrificing a certain amount of traffic flow, but avoiding extreme deterioration of the bandwidth capacity on some connections.