What is UDP (User Datagram Protocol)?
UDP, short for User Datagram Protocol, is one of the transport layer protocols (Layer 4) commonly used on the internet. Like TCP, it operates as an upper-layer protocol to IP.
The UDP header includes source and destination port numbers, allowing for communication specified by ports. Unlike TCP, UDP is a connectionless protocol, meaning it does not require session establishment or termination through handshake mechanisms. It lacks features such as flow control, error control, and congestion control, operating as a message-oriented protocol that sends messages unidirectionally.
Due to its lack of reliability mechanisms, UDP’s tolerance to communication errors is lower, and its reliability is not as high as TCP. However, it is better suited for communications demanding speed and real-time transmission. Additionally, being connectionless, UDP is ideal for multicast and broadcast communications, enabling the simultaneous transmission of data to multiple recipients. Common applications of UDP include:
However, UDP's ability to send packets unidirectionally makes it susceptible to misuse in DoS/DDoS attacks, such as UDP flood attacks where large amounts of UDP packets are sent from multiple computers to overwhelm a network. Additionally, when queries are sent via UDP, the response does not verify the source, making it possible to spoof source IP addresses to perform reflection attacks, targeting victims.