The UDP Protocol UDP also works on top of IP. it adds port numbers, but does not add anything else. Thus, UDP is as unreliable as IP. On the other hand, UDP does not add the overhead of TCP, and is thus suitable for applications that need good response (e.g. audio/video streaming) or that send very small and scarce amounts of data (e.g. the DNS protocol). UDP packets are known as datagrams, and are limited in size (as opposed to TCP streams, which are not limited at all). With UDP, there is no connection establishment - a host just sends data to a listening host, and it arrives there.