To increase addressing capacity of terminals in a packet transmission network (RP) such as the Internet, the identifier (ITe) of a terminal (Te) having a predetermined format included in a network packet (PQ1) transmitted in a client installation (IC) is translated into a predetermined identifier (IPI) of the installation (IC) having said format and included in a network packet (PQ2) which is transmitted in the packet network (RP) to a telephone service provider server and into a port number (Pe1-Pe3) corresponding to the terminal identifier (ITe) and included in a transport packet encapsulated in the packet (PQ2) transmitted in the network, or vice versa. The port number can be allocated dynamically for steps during a call involving the terminal.