Indicates what action to take when the broadcast
rising threshold for a port is reached.
The default action is to forwardBroadcast(2) as usual
for all broadcast frames received from the port. The
other action is to stopBroadcastForwarding(1) frames
until the broadcast reception rate falls to
or below the falling threshold.
The port can also be shutdown in the event of a
broadcast storm with the action disablePort(3).