(IPT, Internet Telephony) Use of IP data connections to exchange voice and fax data that have traditionally been carried over the public switched telephone network.
During the late 1990s, an increasing number of telephone calls have been routed over the Internet. Calls made in this way avoid PSTN charges. Unlike traditional telephony, IP telephony is relatively unregulated.
Companies providing these services are known as Internet Telephony Service Providers (ITSPs). They include telephone companies, cable TV companies and Internet Service Providers (ISPs).
There are still many problems with voice quality, latency, compression algorithms, and quality of service.
Voice over IP is an organised effort to standardise IP telephony.
See also Computer Telephone Integration.