The common name for the suite of protocols developed by the US Department of Defense in the 1970's to support the construction of world-wide internetworks. TCP and IP are the two best-knows protocols and provides for the reliable transmission of data.

This de facto UNIX standard is the Internet communications protocol and has become the global standard for communications. TCP provides transport functions, which ensures that the total amount of bytes sent is received correctly at the other end. UDP (User Datagram Protocol), which is part of the TCP/IP suite, is an alternate transport that does not guarantee delivery. It is widely used for realtime voice and video transmissions where erroneous packets are not retransmitted. TCP/IP is a routable protocol, and the IP part of TCP/IP provides this capability. In a routable protocol, all messages contain not only the address of the destination station, but the address of a destination network. This allows TCP/IP messages to be sent to multiple networks (subnets) within an organisation or around the world, hence its use in the Internet. IP accepts packets from TCP or UDP, adds its own header and delivers a ‘datagram' to the data link layer protocol. It may also break the packet into fragments to support the maximum transmission unit (MTU) of the network.

protocol developed by the US Department of Defense as a means of transferring data between computers. It is used widely throughout the Internet and still used by the US DoD.