VoIP or Voice over IP is a term used to describe the technique of transmitting real time (usually voice) communications over IP networks. This is in contrast to traditional voice communications, which runs over a network of lines using time division multiplexing. VoIP systems can reach “normal” phones (wired and mobile) through gateways connecting the two networks. This technique is used to supply multiple types of products and services:

• PBX systems, where VoIP-enabled equipment creates the organizations internal phone system and operates on the organizations data network;
• hosted or virtual PBX systems, where service providers supply the infrastructure required to supply organizations with the PBX systems (from the prior bullet) without the need for the organization to purchase capital equipment infrastructure;
• consumer phone services, where consumers connect normal phones both to a specialized adapter and to their broadband IP network connection (e.g. cable, dsl), and use a (often 3rd-party) provider for voice calls, typically at a lower cost than traditional phone line suppliers.

Various techniques, such as traditional client/server and peer-to-peer, can be used to facilitate the call setup and tear-down.

See Also

• SIP