These rules are defined in procedures and, in the case of a dial-up connection, are divided into five procedure phases. The individual procedure phases determine the time sequence and correspond in essential parts to the telephony. In the first phase, the dial-up connection is established, and then - as defined in phase 2 - both subscribers announce themselves by name. After this phase, the transmission section is established.
The actual transmission of information takes place in phase 3. Consultations, called error correction in communications engineering, still belong to the third phase. The 4th phase is characterized by the farewell of the interlocutors and the 5th by the termination of the connection. In the case of leased lines, phases 1 and 5 for establishing and terminating the connection are omitted.