User Data-gram Protocol (UDP):
User Data-gram Protocol provides a connection-less data-gram service that offers best-effort delivery, which means that UDP does not guarantee delivery or verify sequencing for any datagram’s. A source host that needs reliable communication must use either TCP or a program that provides its own sequencing and acknowledgment services. The user data-gram protocol is a most important protocol of the TCP/IP suite and is used to send the short messages known as data-gram. Common network applications that uses UDP are DNS, online games, IPTV, TFTP and VOIP. UDP is very fast and light weight. UDP is an unreliable connection-less protocol that operates on the transport layer and it is sometimes called Universal Data-gram Protocol.
UDP messages are encapsulated and sent within IP datagram’s, as shown in the following illustration.