a private dialing plan for the communication of packetized voice on a packet - based network using a signaling protocol such as q . 931 to establish , maintain and release switched connections over the network . the dialing plan uses a “ telephone number ” based on a conventional 10 - digit telephone number , such as the user &# 39 ; s regular telephone number . a leading single digit consisting of a “ 0 ” or a “ 1 ” is added in front of the conventional telephone number . a leading “ 0 ” indicates that the desired call is to be directed to the called party &# 39 ; s on - network computer by means of the internet , while a leading “ 1 ” indicates the call is directed through a special gateway to the called party &# 39 ; s conventional telephone .