User Datagram Protocol

UDP, protocol with no connection required between sender and receiver that allows sending of data packets on the Internet (thought unreliable because it cannot ensure the packets will arrive undamaged or in the correct order)

User Datagram Protocol (UDP) is one of the core protocols of the Internet protocol suite. Using UDP, programs on networked computers can send short messages sometimes known as datagrams (using Datagram Sockets) to one another. UDP is sometimes called the Universal Datagram Protocol.UDP does not guarantee reliability or ordering in the way that TCP does. Datagrams may arrive out of order, appear duplicated, or go missing without notice. Avoiding the overhead of checking whether every packet actually arrived makes UDP faster and more efficient, at least for applications that do not need guaranteed delivery. Time-sensitive applications often use UDP because dropped packets are preferable to delayed packets. UDP's stateless nature is also useful for servers that answer small queries from huge numbers of clients. Unlike TCP, UDP supports packet broadcast (sending to all on local network) and multicasting (send to all subscribers).
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In the Internet Protocol suite, a standard, low-overhead, connectionless, host-to-host protocol that is used over packet-switched computer communications networks, and that allows an application program on one computer to send a datagram to an application program on another computer. Note: The main difference between UDP and TCP is that UDP provides connectionless service, whereas TCP does not.

<protocol> (UDP) Internet standard network layer, transport layer and session layer protocols which provide simple but unreliable datagram services. UDP is defined in STD 6, RFC 768. It adds a checksum and additional process-to-process addressing information [to what?]. UDP is a connectionless protocol which, like TCP, is layered on top of IP.
UDP neither guarantees delivery nor does it require a connection. As a result it is lightweight and efficient, but all error processing and retransmission must be taken care of by the application program.
Unix manual page: udp(4).
[Postel, Jon, User Datagram Protocol, RFC 768, Network Information Center, SRI International, Menlo Park, Calif., August 1980].
(1998-02-11)