The User Datagram Protocol (UDP) is the other major transport layer (Layer 4) protocol in the Internet Protocol (IP) suite, serving as an alternative to TCP. Unlike TCP, UDP is a "connectionless" protocol. It does not establish a connection before sending data, and it does not guarantee delivery, order, or error checking. When an application sends data using UDP, it simply formats the data into a packet (called a datagram), adds a header with source and destination port information, and sends it out to the network. There is no handshake, no sequence numbers, and no acknowledgments.
It is often described as a "fire and forget" protocol. The primary advantage of UDP is its low overhead and speed. By stripping away all the reliability mechanisms of TCP, UDP is much faster and has lower latency. This makes it suitable for applications where speed is more critical than perfect reliability. It is commonly used for real-time applications like video conferencing, online gaming, and live audio/video streaming, where losing an occasional packet is acceptable and preferable to the delays caused by TCP's retransmission mechanism. It is also used for simple query-response protocols like DNS (Domain Name System).
While most instrument control uses TCP for reliability, UDP might be used for broadcasting instrument status updates to multiple monitoring stations on a network.