The User Datagram Protocol (UDP) is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case, referred to as datagrams, to other hosts on an Internet Protocol (IP) network without requiring prior communications to set up special transmission channels or data paths.

What is User Datagram Protocol (UDP)?

User Datagram Protocol (UDP) refers to a protocol used for communication throughout the internet. It is specifically chosen for time-sensitive applications like gaming, playing videos, or Domain Name System (DNS) lookups. UDP results in speedier communication because it does not spend time forming a firm connection with the destination before transferring the data. Because establishing the connection takes time, eliminating this step results in faster data transfer speeds.

However, UDP can also cause data packets to get lost as they go from the source to the destination. It can also make it relatively easy for a hacker to execute a distributed denial-of-service (DDoS) attack.

In many cases, particularly with Transmission Control Protocol (TCP), when data is transferred across the internet, it not only has to be sent from the destination but also the receiving end has to signal that it is ready for the data to arrive. Once both of these aspects of the communication are fulfilled, the transmission can begin. However, with UDP, the data is sent before a connection has been firmly established. This can result in problems with the data transfer, and it also presents an opportunity for hackers who seek to execute DDoS attacks.

user datagram protocol

The benefits and downsides of UDP

User Datagram Protocol has a number of benefits for different types of applications, including:

  • No retransmission delays – UDP is suitable for time-sensitive applications that can’t afford retransmission delays for dropped packets. Examples include Voice over IP (VoIP), online games, and media streaming.
  • Speed – UDP’s speed makes it useful for query-response protocols such as DNS, in which data packets are small and transactional.
  • Suitable for broadcasts – UDP’s lack of end-to-end communication makes it suitable for broadcasts, in which transmitted data packets are addressed as receivable by all devices on the internet. UDP broadcasts can be received by large numbers of clients without the server-side overhead.

At the same time, UDP’s lack of connection requirements and data verification can create a number of issues when transmitting packets. These include:

  • No guaranteed ordering of packets.
  • No verification of the readiness of the computer to receive the message.
  • No protection against duplicate packets.
  • No guarantee the destination will receive all transmitted bytes. UDP, however, does provide a checksum to verify individual packet integrity.

How Does User Datagram Protocol Work?

In comparison to other networking protocols, the process behind UDP is fairly simple. A target computer is identified and the data packets, called “datagrams,” are sent to it. There is nothing in place to indicate the order in which the packets should arrive. There is also no process for checking if the datagrams reached the destination.

Even though User Datagram Protocol comes with checksums, which are meant to ensure the integrity of the data, and port numbers, which help differentiate the role the data plays at the source and destination, the lack of an obligatory handshake presents a problem. The program the user is executing with the help of UDP is left exposed to unreliable facets of the underlying network.

As a result, the data may get delivered, and it may not. In addition, the order in which it arrives is not controlled, as it is in TCP, so the way the data appears at the final destination may be glitchy, out of order, or have blank spots.

However, in a situation where there is no need to check for errors or correct the data that has been sent, this may not pose a significant problem. This is one reason why UDP is used in video applications. Getting the video signal to its destination on time is worth the occasional glitches.

How is UDP Used in DDoS Attacks?

While User Datagram Protocol is arguably faster and a better solution in situations where quick, real-time data reception is a must, it also leaves the receiver open to DDoS attacks.

During a DDoS attack, a site is bombarded with enormous amounts of datagrams. Each time there is an issue, the target computer has to reply with an Internet Control Message Protocol (ICMP) packet. The site’s server cannot handle all this activity and ends up getting “clogged” like a plugged drain. This prevents legitimate communications from getting through – they get a denial of service – and renders the site useless to well-meaning customers and clients who are trying to communicate with it.

UDP leaves a site particularly vulnerable to DDoS attacks because no handshake is required between the source and destination. The source can freely bombard the destination without getting the “OK” to do so.

If an organization limits the response rate that governs when ICMP packets are sent, they can mount a defense against DDoS attacks. It is also possible to respond to UDP traffic using a network of data centers, so fake requests do not overrun a single server.

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What are the applications of the User Datagram Protocol?

UDP can be used for a variety of applications on the internet. The most common type of application is straightforward communication for a small amount of data between two computers in a network. It can also be used for multicasting, in which a single source sends data to multiple recipients on a network. UDP can also be used for routing update protocols and real-time applications in which data needs to be delivered extremely quickly. For example, in online gaming, it is more acceptable to experience a low-quality video or sound for a few seconds than to experience a lag in the game. UDP is ideal for these types of applications where speed of data transfer is the priority.