Communication protocols extend through the human layer too. As long as both ends agree on what that is, the medium that the message uses to get from A to B is a

Communication protocols extend through the human layer too. As long as both ends agree on what that is, the medium that the message uses to get from A to B is arbitrary. With your father, texts are synchronous comms, possibly without requiring an explicit acknowledgement. This may be different for different groups of people. Define what that agreed protocol is and it removes the ambiguity.