User Datagram Protocol (UDP)
UDP operates at the transport layer of the OSI model and performs functions similar to that of TCP, with one notable difference; UDP is a connectionless protocol and does not guarantee data delivery. Both TCP and UDP use IP as its transport protocol.
Because UDP does not need to guarantee data delivery it is much more efficient than TCP, so for applications that don't need the added features of TCP, UDP is much more economical in terms of bandwidth and processing effort. A good example of UDP is an online radio station that sends data but does not confirm data delivery.