User Datagram Protocol. An alternative to Transmission Control Protocol (TCP), but suitable for rather more specific purposes. Like TCP, UDP uses Internet Protocol (IP) to deliver the message to the desired address. UDP differs from TCP in that it is unable to segment a message into packets or to control the order in which the packets are sent/received. Therefore, UDP is suitable for situations where the messages to be sent are small enough not to require segmentation.

However, UDP provides port numbers, which identify separate user request, and a checksum capability, which can be used to verify that the data was transmitted without errors. Neither of these services is available when using TCP.

See also: TCP/IP.