Strategic Upgrade Scheduling and Portfolio Management to Fortify Contested Networks

The nuclear command, control, and communication (NC3) network provides an effective deterrent against adversaries by maintaining robust communication between assets, operators, and decision makers. NC3 must receive a series of upgrades to remain an effective deterrent against evolving threats around the globe. Given a contested network and a portfolio of network upgrades, this research seeks an optimal upgrade schedule to maximize network resilience in support of NC3 modernization. Our research contributes a model that solves a budget-constrained network upgrade scheduling problem (NUSP). The NUSP is a defender-attacker-defender tri-level optimization model that achieves fortification via selecting and scheduling network upgrades. The lower-level defender problem is the shortest path problem, the mid-level attacker problem is the shortest path interdiction problem (SPIP), and the upper-level defenders problem is the NUSP. We present an exact, solvable solution method and propose a simulated annealing (SA) heuristic. The formulation is applied to a large network instance. Using four scenarios, we investigate the effects of attacker budget and risk proles on the optimal upgrade schedule. Results indicate that both attacker budget and risk prole affect the optimal upgrade strategy. Moreover, the optimal upgrade schedule provides greater network resilience than the myopic (i.e., baseline) upgrade schedule.