Voice over IP (VoIP) is a transmission medium in which voice signals are transmitted over IP data networks. With VoIP, the phone system and IP network translate between voice and net- work signals and between phone numbers and IP addresses. You can make a telephone call and the signal will be transmitted over your network connection and transferred to the standard phone system if the called party does not have VoIP service. Conversely, when a caller dials a phone number that maps to a VoIP device, VoIP routes the call to the IP host.
Advantages and Limitations of VoIP
VoIP is rapidly being adopted because it relies on the existing, robust router infrastructure true of IP networks and the near-universal implementation of the IP protocol. It also eliminates per-call costs because it uses the existing Internet connectivity channel. It does have some drawbacks. The major problem is that IPv4 does not provide for time-sensitive data. On a busy network, voice data is packet switched with other network data and delivery can slow down or become unreliable.
There are many VoIP clients, but some of the more popular client applications avail-able to consumers are Vonage™, Skype™, magicJack™, and Packet8.