IP telephony (Internet Protocol telephony)

IP telephony (Internet Protocol telephony) is a general term for the technologies that use the Internet Protocol's packet-switched connections to exchange voice, fax, and other forms of information that have traditionally been carried over the dedicated circuit-switched connections of the public switched telephone network (PSTN). 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.

IP telephony service providers include or soon will include local telephone companies, long distance providers such as AT&T, cable TV companies, Internet service providers (ISPs), and fixed service wireless operators. IP telephony services also affect vendors of traditional handheld devices.

Currently, unlike traditional phone service, IP telephony service is relatively unregulated by government. In the United States, the Federal Communications Commission (FCC) regulates phone-to-phone connections, but says they do not plan to regulate connections between a phone user and an IP telephony service provider.

VoIP is an organized effort to standardize IP telephony. IP telephony is an important part of the convergence of computers, telephones, and television into a single integrated information environment. Also see another general term, computer-telephony integration (CTI), which describes technologies for using computers to manage telephone calls.

This was last updated in November 2010

Next Steps

Customize IP phones with address books, ringtones and other functions.

IP telephony is more complex and versatile than TDM telephony. Here, you will learn how to evaluate different VoIP vendors before buying.

Users can extend their IP phones to their desktop, allowing more mobility and connectivity with Cisco's UCM VoIP technology. This series also covers the Panasonic VoIP KX-TDE system, which is designed to meet the needs of business of all sizes and needs; the NEC VoIP Univerge product series, which includes includes several IP phones with features such as click to call; the features of ShoreTel's VoIP phone systems; and the Mitel 3300 VoIP platform, which supports IP phones for both large and small organizations; and Adtran NetVanta series.


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