Specifies the load balancer type. Choose EXTERNAL for external
HTTP(S), SSL Proxy, TCP Proxy and Network Load Balancing. Choose
INTERNAL for Internal TCP/UDP Load Balancing. Choose
INTERNAL_MANAGED for Internal HTTP(S) Load Balancing.
INTERNAL_SELF_MANAGED for Traffic Director. A backend service
created for one type of load balancer cannot be used with another.
For more information, refer to Choosing a load balancer.