User Datagram Protocol (UDP) represents the Transport Layer in the Open System Interconnection (OSI) model. The Transport Layer is responsible for end-to-end connectivity and reliability.

Unlike Transmission Control Protocol (TCP), UDP is a connectionless protocol (there is acknowledgement that data was received), so it does not guarantee that data was received or that it was received in the order in which it was sent. Without having to ensure that each data packet arrives in the correct sequence, UDP is faster and more efficient. Thus, it is useful for situations in which time is an issue.UDP is often used with its typical Network Layer partner, Internet Protocol (IP), and thus has the combination of UDP/IP.

See also: IP, TCP/IP, UDP