Consistency is Not Easy: How to Use Two-Phase Update for Wildcard Rules?

The recent proposed two-phase mechanism is a provable theory to achieve consistent updates for SDN. However, how to make it work for practical rules is important yet unsolved-(1) two-phase mechanism requires that rules in the new configuration after an update are assigned with a distinct version number from rules in the old configuration before an update; but (2) setting rules in each configuration with a distinct version number causes serious rule-space overheads in practice due to the sophisticated “covered” relationships between practical wildcard rules. In this letter, we design a simple yet generic solution for the problem. By using well-designed wildcard-based version number matchings, we simplify the update procedure, make a stream of updates easy to be processed in parallel, and avoid all unwanted rule-space overheads. We think that our mechanism bridges the gap between the theory of two-phase consistent update and the practical issue of how to use it for today's networks.