'Start to migrate the network of an instance.'

def migrate_instance_start(self, context, instance, migration):

    flavor = instance.get_flavor()
    args = dict(instance_uuid=instance.uuid, rxtx_factor=flavor['rxtx_factor'], project_id=instance.project_id, source_compute=migration['source_compute'], dest_compute=migration['dest_compute'], floating_addresses=None)
    (multi_host, addresses) = self._get_multi_addresses(context, instance)
    if multi_host:
        args['floating_addresses'] = addresses
        args['host'] = migration['source_compute']
    self.network_rpcapi.migrate_instance_start(context, **args)
