[User] Data Link [Boss] Mail Service
When the Mail Service Department, receives the packets it adds the physical address of the office, which is the house number, and then makes a check of the packets for any mismatch or loss by the above layers. Then places the result on the packets, and now what we have is a Frame. Again the Frame has to have some kind of medium so that it can reach the receiving party. It decides the medium and then hands over to the decided medium.