Internet Protocol is the most widely used open system protocol suite for network communication. Used for both WAN and LAN connections, it consists of two main components: Transmission Protocol Unit (TCP) and the Internet Protocol (IP). IP, part of the Layer 3 network, contains addressing and control information that enables the routing of data packets. It has two main functions: to provide data delivery without requiring connections through an inter network; and to provide the breakage of data packages and their subsequent reassembly.
IP PBX (Internet Protocol Private Branch Exchange) is a business used telephone system that is responsible for delivering voice or video over a data network, and operates together with PSTN (Public Switching Telephone Network). In order to reduce the expenses incurred by long distance voice calls, VoIP (Voice over Internet Protocol), when combined with conventional PBX, can provide a single network for normal voice function and data transfer, thereby cutting back on long distance expenses. IP PBX systems can be both hardware and software.