ITSP - Company providing IP Telephony

IP Telephony is a two-way transmission of voice over a packet-switched IP network, which is part of the TCP/IP protocol suite.

The terms "IP telephony" and "voice over IP" (VoIP) are synonymous. However, the term VoIP is widely used for the actual services offered (see What is VoIP? for more details), while IP telephony often refers to the technology behind it. In addition, IP telephony is an umbrella term for all real-time applications over IP, including voice over instant messaging (IM) and videoconferencing.