High Availability (HA) is one of the most critical requirements in real network operation. Provisioning redundancies, enabling failure detections and notifications, supporting a state synchronization, and invoking failure mitigation have been the essential steps to achieve the HA feature. Software-DefinedNetworking (SDN) is an emerging networking paradigm that centralizes the control plane by separating it from the data plane.
In this paper, we identify that SDN poses more complex HA issues due to a newnetwork domain between the control and data planes which is called the control path. It poses many critical challenges on the existing HA mechanisms to achieve the same Service Level Agreement (SLA) of HA for the services in the SDN environment. To address this problem, we propose and implement several control path HA algorithms that enhance performance as well as simplify management of control path HA.