user datagram protocol (UDP)
The User Datagram Protocol (UDP) is a connectionless transport protocol for data exchange between computers. The UDP protocol was defined so that application processes can send datagrams directly and thus fulfill the requirements for transaction-oriented traffic. The UDP protocol builds directly on the underlying IP protocol and is characterized by low overhead and short latency.
The UDP protocol has a minimal protocol mechanism and does not guarantee the delivery of a datagram to the destination partner, nor are any precautions taken against duplication or sequence reversal. The functional scope of the UDP protocol is therefore limited compared to the TCP protocol. It is limited to the transport service, multiplexing of connections and error handling.
In the case of the transport service, correct data transmission to the recipient is not ensured because it operates without an acknowledgement mechanism. Therefore, lost data packets cannot be sent again. In contrast to the TCP protocol, which works connection-oriented, the UDP protocol, which works connectionless, does not establish an active connection between the stations, but sends the individual data packets into the network completely independently of each other.
By using ports, several communication destinations can be selected in one computer. The ports are identified by port numbers, whereby these numbers are partially reserved for certain processes.
The UDP header
Since the UDP protocol has minimal error handling only under certain implementations, it is up to the higher layers to detect errors and make a correction. The UDP header comprises only 8 bytes, in contrast to the TCP header, which comprises 40 bytes. The data fields of the UDP header include the source address and destination address, the length field where the UDP header length is entered, and the checksum field.
The UDP protocol is described in the TCP/IP standard document RFC 768, among others. It is used wherever a low delay time and deterministic behavior are required.