# Which SDN controller to use. Valid options are 'opendaylight', 'onos',
# 'opendaylight-external', 'opencontrail' or false. A value of false will
# use Neutron's OVS ML2 controller.
# Which SDN controller to use. Valid options are 'opendaylight', 'onos',
# 'opendaylight-external', 'opencontrail' or false. A value of false will
# use Neutron's OVS ML2 controller.