User Datagram Protocol

The User Datagram Protocol (UDP) is a thin layer on top of the Internet protocol. It merely provides a mechanism to identify different endpoints on a single host by means of ports. No connections or reliability are provided (see TCP for that) -- UDP just deals with single packet delivery, provided by the underlying IP. Most music streams sent over the internet use UDP, to reduce server overhead.

UDP packets (also known as datagrams) contain, in addition to the lower level headers, an UDP header, which consists of a checksum, the packet length, plus source, and destination ports.

The ports are 16-bit entities, so that a maximum of 65535 different endpoints are possible within a single IP address.

See TCP/IP for the big picture.