An IP PBX is a private branch exchange or switchboard that is designed to provide video and/or voice communication services over IP data networks. That is, using IP telephony technology, a phone service can be provided through, for example, a company’s IP virtual private network (VPN). When the IP network used is the internet, one can also speak of “Internet Telephony”, which is just one example of a Voice over IP (VoIP) service. There are significant differences in performance guarantees and of voice quality between VoIP on a VPN and through Internet.
Today, the vast majority of telephone exchanges installed are IP PBX: