In the past, organizations have deployed separate networks to handle traditional voice, data, and video traffic. Each with different transport requirements, these networks were expensive to install, maintain, and reconfigure. Furthermore, since these networks were physically distinct, integration was difficult, if not impossible, limiting their potential usefulness.

IP telephony blends voice, video, and data by specifying a common transport, IP, for each, effectively collapsing three networks into one. IP telephony enables this over existing IP-based LANs, WANs, and the Internet. The result is increased manageability, lower support costs, a new breed of collaboration tools, and increased productivity.

Specifically, IP telephony uses open IETF and ITU standards to move multimedia traffic over any network that uses IP, offering users both flexibility in physical media (for example, POTS lines, ADSL, ISDN, leased lines, coaxial cable, satellite, and twisted pair) and flexibility of physical location. As a result, the same ubiquitous networks that carry Web, e-mail, and data traffic can be used to connect to individuals, businesses, schools, and governments worldwide.

TAPI 3.0 is an evolutionary API that supports convergence of both traditional PSTN telephony and telephony over IP networks.

IP telephony allows organizations and individuals to lower the costs of existing services, such as voice and broadcast video, while broadening their means of communication to include modern video conferencing, application sharing, and whiteboarding tools.

Possible applications for IP telephony include telecommuting, real-time document collaboration, distance learning, employee training, video conferencing, video mail, and video on demand.