The following diagram shows how remote invocation works for inter-ORB communication. It shows that the clients that interacted have created IDL Stub and IDL Skeleton based on Object Request Broker and communicated through IIOP Protocol.

To invoke the remote object instance, the client can get its object reference using a naming service. Replacing the object reference with the remote object reference, the client can make the invocation of the remote method with the same syntax as the local object method invocation. ORB keeps the responsibility of recognizing the remote object reference based on the client object invocation through a naming service and routes it accordingly. This configuration might have been more complex if you would have had cluster and load balancer configurations in place.