Voice over Internet Protocol (Voice over IP, VoIP and IP telephony) is a technology of voice communications and multimedia sessions over Internet Protocol (IP) networks, e.g. the Internet.
The VoIP communication is similar in many ways to the traditional digital telephony system. It includes digitization of the analog voice signals, signaling, encoding and channel setup. However, the packets and transmission works as IP packets in digital information, over a packet switched network; instead of being transmitted over a circuit-switched network like traditional PSTN.
VoIP calls use media protocols to encode messages. Different codecs are used based on the encoding methods. Based on network bandwidth and application requirements, some of these codecs optimizes the stream. High fidelity stereo codecs are used as well as compressed, narrow band codecs. Popular codecs include versions of G.711, an open source codec named iLBC, G.729 codec that uses 8 kbit/s each way, and several others.