VoIP (voice over internet protocol), IP telephony, internet telephony, VoI (voice over internet).
Several terms are used to describe the process of sending phone calls using IP (internet protocol) rather than the PSTN (public switched telephone network), but different people don't always mean the same thing when they use the terms.
So how do you sort out the linguistic confusion that sometimes arises when discussing the subject?
It helps to describe the concepts first then how the phrases are applied to them.
First, there is the process of simply routing calls using IP to avoid toll bills, while beginning and ending the call on the PSTN or an organisation's PBX (private branch exchange) system.
Then there's the broader system of integrating voice, data and, potentially, other formats such as video on one network, using IP (which is not to be confused with the public internet) to send the voice or data in packets down one single wire in an organisation's private network.
Generally, internet telephony and VoI refer to the first process and VoIP and IP telephony to the second, but VoIP is sometimes used to describe the former.
Jeff Herbert, managing director of Auckland systems integrator Lanscape, which implements Cisco’s IP telephony products, takes VoIP to mean the former, more limited process and talks of IP telephony, Cisco's preferred term, for the full offering.
“IP telephony is where voice is transmitted over IP from end to end,” Herbert says, whereas he considers VoIP to mean when a call is initiated and ended on the conventional telephone system, but routed through the internet in order to avoid toll call costs.
“The only thing VoIP utilises is the cost savings on toll charges – it doesn’t bring any other benefits to an organisation.”