First voice over internet protocol (VoIP)

Free telephone calls over the internet are a feature of everyday life in the 21st century. This way of communicating has its roots back in 1974. The first demonstration of voice-over-network communications was carried out in August 1974 using Network Voice Protocol (NVP) over the US Department of Defense's Advanced Research Projects Agency Network (ARPANET), one of the first operational computer networks. This enabled multiple computers to "talk" to each other over a single wire connection (using what is known as "packet switching" – a process in which data from each computer is broken into packets of information sent one after another). The NVP protocol was developed in 1973 by a team led by Danny Cohen. It is essentially the same packet-based voice-communication network as implemented in today's VOIP communications.