FLIP the (Flow) table: Fast lightweight policy-preserving SDN updates

We propose FLIP, a new algorithm for SDN network updates that preserve forwarding policies. FLIP builds upon the dualism between replacements and additions of switch flow-table rules. It identifies constraints on rule replacements and additions that independently prevent policy violations from occurring during the update. Moreover, it keeps track of alternative constraints, avoiding the same policy violation. Then, it progressively explores the solution space by swapping constraints with their alternatives, until it reaches a satisfiable set of constraints. Extensive simulations show that FLIP outperforms previous proposals. It achieves a much higher success rate than algorithms based on rule replacements only, and massively reduces the memory overhead with respect to techniques solely relying on rule additions.