Flow-level consistent update in SDN based on K-prefix covering

In Software Defined Networks (SDN), the configuration inconsistency during updates is one main source of network instability. Even if the validity of the initial and final configurations is guaranteed, the interim complex and inconstant network states might cause routing conflicts and transmission disruption. Therefore, an efficient updating scheme of configuration consistency is required. Current schemes solve the problem of packet-level configuration consistency very well, but perform poorly for flow-level configuration consistency. In this paper, we provide a new scheme to guarantee flow-level consistency during configuration updates in SDN. In our scheme, the controller 1) collects the existing flow information; 2) computes K optimal prefixes covering the existing flows; 3) installs the new rule and K old sub-rules with lower and higher priorities respectively. We design the K-prefix covering algorithm by dynamic programming, which computes the K optimal prefixes with the minimum covering space. Therefore, the new rules will be activated for the maximum space. We evaluate our scheme and algorithm by comprehensive experiments. The results show that our scheme reduces the transition time to 10% of the current periodical direct division scheme.