Dealing with misbehaving controllers in SDN networks

The logical centralized approach in the control of SDN networks allows an unprecedented level of programmability in the network, but also implies the vulnerability in the case of misbehavior of the controller, due for example to software bugs, hardware problems or hacker attacks. In our work we propose to exploit the diversity offered by multiple controllers to manage the network switches and detect misbehaviors whenever one controller issues different OpenFlow instructions for the data plane with respect to the others. We design a behavioral checker, denoted as BeCheck, that acts as a transparent relay in the interaction between the network switches and the controllers. We propose and investigate different policies to relay the messages and to detect the controller misbehavior. We implement and validate our approach in a simple testbed, showing the possible tradeoff between detection reliability and controller reactivity perceived at the switches.