UDP

User Datagram Protocol

Hosts run multiple processes and services and nothing within IP gives us the ability to connect between a requesting application on a client and the service it needs to consume on a server.

User Datagram Protocol is a Transport Layer protocol which adds a simple header which gives us this capability. UDP was originally used for traffic where reliable delivery was not important. If I am checking for a network address and I do not get a response, I just check again!

UDP is also used in applications where we need a stream of data and cannot request a resend of a missing packet. For example, in a video stream, if I lose a frame, there is no point resending it, the user will already be beyond the point at which the frame was lost before they receive the resend. UDP is fast, has low overhead and will produce optimal results where the underlying network is reliable and has a low bit error rate (BER).

UDP includes no functionality for identifying missing data or requesting resends, this is the job of higher level protocols.