MPTCP based in-band controlling for the software defined networks

In Software Defined Networking (SDN), connections between the controller and the switches are maintained in two ways: out-of-band and in-band. In out-of-band controlling, the control channels are constructed via separate links. However, due to several reasons, sometimes in-band controlling is needed instead of out-of-band controlling. In in-band controlling, the data paths are used for control channels. In this situation, the availability of control channel is crucial for the operation of SDN. In this paper, we focus on improving the availability of in-band control channel under the link failure situations. Basically, we apply MPTCP on the controlling channel for high availability. We consider the situation where the controller is connected to a subset of switches and control channels to other switches are constructed through the data paths. To provide the availability of control channel, the paths from a switch to the set of adjacent switches (i.e. gate switches) to the controller should be disjoint as much as possible. In this situation, the most challenging problem is to select the set of gate switches to connect to the controller. As exhaustive search might be time consuming, we propose two simple heuristic algorithms (Path Length First and Disjoint Path First) to find the set of gate switches which provide high availability. Through simulations, we show that the Path Length First runs much faster than the exhaustive search but shows similar performance as that of the exhaustive search.