UDP's Connectionless Nature

User Datagram Protocol UDP is a Transport Layer protocol used for connectionless communication between applications.

Unlike TCP which is connection oriented, once a UDP datagram is sent, there are no mechanisms in place to keep track of sent datagrams, nor are there any reliability or flow control mechanisms. Indeed, the UDP header is quite small, and contains only the source and destination port numbers, the length of the datagram, and a checksum for detecting corrupted datagrams. If a UDP datagram is lost or corrupted or arrives too late for the reconstruction of the original data, it is simply discarded. UDP does not concern itself with reconstruction or error correction. These tasks fall to higher-level protocols (i.e. at the Application Layer).

Connectionless communication may seem bad, but it has many advantages over connection-oriented commoditization. It is much more efficient since it has less overhead in both header size as well as computational requirements of the involved network devices.

For this reason, UDP is used by many applications that require low latency and can tolerate some degree of data loss. For more information about applications that leverage UDP, take a look at UDP Use Cases.

Links:

https://networklessons.com/network-fundamentals/introduction-to-tcp-and-udp