Packet network telecommunication systems, especially Internet Protocol (IP) telephony removes the need of explicit installing of TSP (TAPI service provider) software or other telephony software at each workstation. Application server software or corresponding control software is arranged to take care of all call control actions on behalf of the phone client software so that the phone client software only needs to receive and transmit speech data streams, and to communicate all control messaging from and to the particular phone client software via the communication link between the control software and the phone client software. Since modern operating systems include support for the user interface devices as well as transmitting and receiving real-time data streams, the phone client software does not require any specific interfacing software to be installed on the client workstation.