UDP

The User Datagram Protocol allows applications to exchange data across the network with a minimum of overhead. It is a connectionless, unreliable protocol. In this context, unreliable means that there is no method built into the protocol for verifying that the data reached the destination. The first 32-bit word of the UDP header contains a 16-bit Source Port and 16-bit Destination Port to deliver the data to the correct application. The second word of the UDP header contains the length of the UDP packet and a checksum to determine whether or not the packet data is corrupted. UDP is used for many reasons. For simple applications or applications sending small amounts of information, the overhead of a reliable connection may be considerably more than simply retransmitting an entire message. In this case UDP is the more efficient Transport Layer Protocol choice. Applications that use a "Query-Response" style of communication are excellent choices for UDP. The response can be used as an acknowledgment to a query, and if the response is not received within a set time then the query can be retransmitted. Many applications provide their own methods for insuring reliable data exchange and the overhead of adding additional verification is not efficient. These, too, are good choices for the UDP protocol. The User Datagram Protocol is documented in RFC 768.