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Voice over Internet Protocol (VoIP)*

Voice over Internet Protocol (VoIP) is a technology that enables people to make telephone calls over an Internet broadband connection instead of over traditional analog lines.  VoIP works by converting analog voice signals to digital format, compressing those signals into Internet Protocol (IP) packets and transmitting them over the Internet.  It facilitates communication between and among computers and telephones.

People can access VoIP services using an adapter, an IP phone or a computer.  Using adapters, callers can connect a standard telephone to a computer or an Internet connection.  IP phones use special Ethernet connectors to attach directly to a router.  The easiest way to use VoIP is through a computer equipped with software, a microphone, speakers, a sound card and an Internet connection.  Most people have everything except for the software, which is supplied by the VoIP service provider.

The standard system for communications, the Public Switching Telephone Network (PSTN) uses circuit switching.  Placing a telephone call opens a circuit, which remains open in both directions throughout the call's duration.  This system has demonstrated inefficiencies because at any given time, only one person is talking and much of the conversation is dead air.  The dead space deprives an opportunity to use the circuit for anything else.  Except for the change from using copper wires to using fiber optics with copper wires connecting the home (the so-called "last mile"), this system has existed for more than 100 years.

VoIP uses packet switching, the protocols that operate the Internet.  Instead of routing calls over a dedicated line as in circuit switching, data packets flow through a network along thousands of possible paths.  Computers chop calls into data packets, each containing an address instructing network devices where to send them.  These packets are sent from router to router until they reach their destination.  The receiving computer uses instructions within the packets to reassemble the data.  If the call terminates with a regular telephone, the signal will be converted back to an analog signal before it is delivered to the circuit.  Modern compression technology can shrink the size of each packet by removing the dead air.  Several calls now can occupy the same amount of space using capacity efficiently.

VoIP's advantages over traditional telephony include lower costs per call, lower infrastructure costs, and new advanced features.  In addition, users can take their home phones with them and call from anywhere there is a broadband connection.  They do not even require additional phone lines.

However, VoIP does require a broadband connection and that connection must remain active, creating security concerns.  Given the heavy use of limited bandwidth and use of packet switching instead of a dedicated circuit, some data packets may be lost leading to gaps, periods of silence or clipped speech in conversations.  Furthermore, some VoIP services may not work during a power outage, connect to 911, identify the location of the 911 caller, or offer directory assistance.

The future of VoIP depends on settling the regulatory environment, developing standardized protocols to ensure interoperability among VoIP providers and with the PSTN, and increasing quality and reliability.  The technology must make VoIP as user-friendly and reliable as the PSTN before it will become a substitute.

* Sources: Jeff Tyson and Robert Valdes, How VoIP Works, (visited October 7, 2004) http://computer.howstuffowrks.com/ip-telephony.htm.
International Engineering Consortium, Voice over Internet Protocol, (visited October 7, 2004) http://www.iec.org/online/tutorials/int_tele/.