VoIP is a voice over internet protocol network service. Initially, the most widely deployed network infrastructure in the world was the telephone network. Data transmission therefore had to be adapted to a support that had never been designed for it, and this was done using modems. Today the situation is almost the reverse: the most widely deployed and above all flexible network, because it is digitised, is the internet and its IP protocol. It is this infrastructure which is now used to transmit everything, and voice transmission must now be adapted to this network, designed for data. The ever faster speeds of the internet trunks, the "quality of service" offers such as guaranteed speed and the provision of an equivalent to the SS7 telephone signal system (setting up and termination of communication, service complement management e.g. for ring tone or line transfer) form the basis of an effective internet telephone transmission service.