IP telephony IP Technology (Internet Protocol telephony) is a general term for the technologies that use the Internet Protocol connection to exchange voice, fax, and other forms of information that have traditionally been carried over the dedicated networks of a private telephone network. Using the Internet, calls travel as packets of data on shared lines, avoiding the tolls of the PSTN. The challenge in IP telephony is to deliver the voice, fax, or video packets in a dependable flow to the user. Much of IP telephony focuses on that challenge.