It makes routing decisions at either the transport layer (TCP/SSL) or the application layer (HTTP/HTTPS).
It requires a fixed relationship between the load balancer port and the container instance port.
Listeners
To start using using CLBs, you must configure one or more listeners.
Listener:
A process that checks for connection requests.
It is configured with a protocol and a port for front-end (client to load balancer) connections, and a protocol and a port for back-end (load balancer to back-end instance) connections.