UDP is a simple, datagram-oriented, transport layer protocol: each output operation by a process produces exactly one UDP datagram, which causes one IP datagram to be sent. This is different from a stream-oriented protocol such as TCP where the amount of data written by an application may have little relationship to what actually gets sent in a single IP datagram.
Figure 11.1 shows the encapsulation of a UDP datagram as an IP datagram.
Figure 11.1. UDP encapsulation.
RFC 768 [Postel 1980] is the official specification of UDP.
UDP provides no reliability: it sends the datagrams that the application ...