8. UDP: unreliable transport service

The User Datagram Protocol (UDP) enables applications to exchange datagrams. This UDP protocol uses the notion of "port" to distinguish between the different applications running on a machine. In addition to the datagram and its data, a UDP message contains both a source and destination port number.

UDP is based on the services of the Internet Protocol, and provides an offline service without error recovery. It uses no acknowledgement, does not re-sequence messages, and has no flow control. UDP messages can be lost, duplicated, re-sequenced or arrive too late to be processed.

In conclusion, UDP provides the simplest possible transport service for applications. In the absence of a guarantee, applications lose only a minimal amount of time in processing the interface with the transport layer. Applications needing rapid access to remote data,...