UDP, User Datagram Protocol

UDP is often referred to as an alternative to TCP (Transmission Control Protocol). When combined with Internet Protocol, it is sometimes termed as UDP/IP. Similar to TCP, UDP uses Internet Protocol to obtain messages from a data unit, more commonly known as datagram. In contrast to TCP, it does not offer the service of diving messages into packets and managing them. To be more specific, UDP does guarantee the sequencing of arriving data packets. For this reason, the program or device using UDP is responsible for making sure messages are received in entirety and in the correct order. UDP offers two services not provided by Internet Protocol: port numbers that help to distinguish requests from different users, and a checksum feature to ensure that data has arrived intact. In the OSI (Opens Systems Interconnection) communication model, both UDP and TCP are a part of layer 4, the Transport Layer.