Consistent SDN Rule Update with Reduced Number of Scheduling Rounds

Consistent operation of software-defined network (SDN) switches during the transient periods of forwarding rule updates is a critical issue. This paper studies the problem of updating SDN rules, while preserving two essential security and performance consistency properties: (1) Waypoint Enforcement which mandates that all packets traverse a specific checkpoint (e.g., firewall), and (2) Loop-Freedom that prevents forwarding packets along a loop. To guarantee these properties, we schedule rule updates in multiple rounds. To reduce the time that the network stays in the transient period of updating the switches, we have to solve the NP-hard problem of minimizing the number of update rounds. To this end, we design a fast algorithm called RRS which can be applied to very large networks. Our experiments on a large dataset of 28K scenarios show that RRS achieves a 323x improvement in the median of execution time compared to solving the exact Mixed Integer Program (MIP) formulation.