User Datagram Protocol

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user datagram protocol

[‚yüz·ər ′dad·ə‚gram ‚prōd·ə‚kȯl]
A communications protocol providing a direct way to send and receive datagrams over an IP network but with few error recovery resources, used mainly for broadcasting over a network, for example, with streaming media.

User Datagram 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 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].


(User Datagram Protocol) A TCP/IP protocol that is widely used for streaming audio and video, voice over IP (VoIP) and videoconferencing. UDP is considered an unreliable delivery protocol because it does not check for errors. When transmitting voice and video, there is no time to retransmit erroneous or dropped packets. In contrast, when financial and other data are transmitted, TCP is used, which does check for errors.

UDP is "connectionless" and does not use a handshake to start a session like TCP does. For example, in a broadcast session with multiple destinations, UDP does not set up a connection with each receiver beforehand. See TCP, TCP/IP and RTP.

UDP Within an Ethernet Frame
A UDP packet is framed just like a TCP packet. This shows a UDP packet in an Ethernet frame ready for transmission over the network.

The Transport Layer of TCP/IP
The transport layer of the TCP/IP protocol defines both unreliable (UDP) and reliable (TCP) delivery methods.