Overview

Internet Protocol (IP) telephony is the emerging communications technology arising from the convergence of the worldwide data infrastructure and the telecommunications network. Until now, the voice world and the data world have been largely separate. Voice traffic moves on circuit-switched networks where a fixed path is established at call setup and maintained for the duration of the call. Network resources are allocated to the call, leading to a logical model of time-based pricing. Over the years, millions of millions of dollars have been invested in circuit-switched technology, and these networks are considered extremely reliable pretty much worldwide. Voice traffic growth is in the single digit category.

Data traffic has moved on packet-switched networks. Messages or files are broken up into small packets, and each packet is sent out onto the network on its own, typically with header information containing the needed destination address and other descriptors. The series of packets moves through the network individually, and different packets may take different paths through the mesh of routers and switches. Packets do not necessarily arrive at the destination in the same order they left the sender, and some packets may be lost along the way. Network resources are shared, however, leading to a very efficient architecture. Often, packet-switched network access is priced at a fixed rate, depending on guaranteed bandwidth, but sometimes the network is priced on a usage basis, with users charged for the number of bytes they transmit.

The latest hype in the industry is the convergence...