The method used to break data into small pieces, called packets, to send them from one computer to another across the Internet. IP is used to send a single chunk of data (in several packets) across various routes on the Internet to a gateway destination. At this point, a second protocol, called Transmission Control Protocol (TCP), reassembles the packets and completes the data transmission. IP and TCP work so closely together that they are often referred to as a single protocol (TCP/IP), even though they are distinct. Each computer connected to the Internet has a unique IP address.