Connection state between an OpenFlow
instance and a controller. The state 'void'
implies that there is no connection. The state
'backoff' represents a state where the device
is attempting to reconnect to the controller
at increasing intervals of time. The state
'connecting' represents a state where the
device is in the process of connecting to the
controller. The state 'active' implies that a
connection has been established and that the
controller is responsive. The state 'idle'
implies that the connection is idle and
waiting for a response.