From the telephone to the SIP

This article describes the evolution of the switched telephone network towards the new SIP-based VoIP architectures. The presentation begins by reviewing some basic concepts inherent in the switched telephone network (semaphore signaling, access network architecture). It also focuses on the evolution of the PSTN (Public Switched Telephone Network) towards ADSL access, making operated VoIP services available, and the positioning of NGN (Next Generation Networks) techniques in this context. This is followed by a brief review of the history of the various VoIP solutions. The presentation ends with a presentation of the SIP protocol, illustrating how it works using protocol traces collected on a network using the SIP protocol.