Transmission Control Protocol/Internet Protocol. TCP/IP is the foundation protocol used in communicating on the Internet, but it can also used in private networks (that is, intranet or extranet).

The higher TCP layer transforms the message or file to be sent into packets, which are then reassembled into the original format by another TCP layer resident in the receiving end.

The lower IP layer takes care of providing each packet with the proper destination address. When the packets are sent, they do not necessarily go via the same route, but the address found in each packet ensures that they all end up in the right destination.

See also: UDP.