Apllication load-balancers may have a 1:many FQDN:load-balanced-service relationship, whereas GLBs have a 1:1 FQDN:load-balanced-service relationship. Application load-balancers (ALBs) typically present to the consumer with one ore more IP address, which may be abstracted as an FQDN. A single client-facing FQDN can be sufficient for an ALB to act as a load-balancer for multiple different applications. Because it is inline for the actual application data plane, the ALB can perform application-layer inspection to classify requests for different URIs to different back-end resource pool. It can likewise instantiate TCP listeners on multiple ports using the same IP address, and map each TCP port to a different backend resource pool. In this scenario, an ALB with a single FQDN and single virtual-IP address can independently distribute traffic for multiple backend load-balanced services. While a single FQDN can suffice for ALBs to independently manage load-balancing for multiple services, the same is not true of GLBs. This is true is all cases, but is especially significant for Kubernetes workload.
FQDN Proliferation
Unlike application load-balancers or inline global load-balancers, DNS-global load-balancers require a unique FQDN for each load-balanced service.