Optimization of SDN Flow Operations in Multi-Failure Restoration Scenarios

Flexible network configuration in software-defined networks makes it possible to dynamically restore flows. To this end, network devices carry out flow operations (i.e., adding or removing flow-entries to/from the flow-tables) to re-route the disrupted flows. Current flow restoration techniques do not consider the number of operations, and hence, are inefficient in disaster scenarios. We aim to minimize the number of operations in such cases and formulate integer programs to find a path: 1) with the lowest path cost requiring up to a given number of operations; 2) requiring the fewest possible operations; and 3) with a Dijkstra-like path cost requiring minimum operations. We study the tradeoff between path cost and the number of operations and prove that the second and third problems are polynomial-time solvable. We propose optimal/suboptimal algorithms with Dijkstra-like complexity that find nearly-optimal solutions. The simulation results show that our methods reduce the number of operations up to 50%, and the best performance is achieved when the number of failed links is small.