Improving the Fault-Tolerance Under Software-Defined Network Based on New Sight of Agreement Protocol

With the rapid development of the Internet technologies, network architectures have been improved continuously. A novel network topology called software-defined network (SDN) has been proposed to enhance the performance of network. Basically, the goals of constructing the SDN network are to achieve faster service deployment, greater flexibility in managing the network, and provisioning while reducing operational costs. So far, most researches have been done to ensure the consistency and reliability on control plane of SDN. However, the consistency and reliability on the data plane of SDN has been neglected. Based on the reasons above, the fault tolerance issue needs to be studied to increase the consistency and reliability of the SDN network. One of the most important problems of fault tolerance issue is the Byzantine Agreement (BA) problem. The goal of BA problem is to make the fault-free processors achieving an agreement to ensure the system working normally even if the faults persist. Unfortunately, the traditional solution is not suitable for the SDN network. Hence, the BA problem should be revised under the SDN network. In this paper, the new kind of failure type called path fault is discussed to adapt to real world. It is because that the routing path between source and destination switch may have faulty influence. Subsequently, a path-based agreement protocol is proposed to solve the BA problem to help all the data be transmitted to the destination even when there are some faulty switches exist in the SDN network. Here, the proposed protocol only requires the minimum number of rounds of message exchange and can tolerate the maximum number of faulty paths for ensuring the consistency and reliability of the SDN network.