UDP Header | UDP checksum example | Why UDP Protocol is used? | Realtime application of UDP

Introduction of UDP

There are two transport layer protocols: TCP and UDP. TCP – Transmission control Protocol and UDP – User Datagram Protocol. In this post, we will discuss about UDP.

UDP stands for User Datagram Protocol. UDP is a simple, datagram-oriented transport layer protocol. UDP has been designed to transfer data packet over internet. UDP is connectionless protocol provides no reliability or flow control mechanisms. It also has no error recovery procedures. Several application layer’s protocols such as TFTP and the RPC use UDP. UDP makes use of the port concept to direct datagrams to the proper upper-layer applications.  UDP serves as a simple application interface to the IP.

Requirement of UDP:

TCP proves to be an overhead for certain kinds of applications. The Connection Establishment Phase, Connection Termination Phase etc of TCP are time consuming. To avoid this overhead, certain applications which require fast speed and less overhead use UDP. UDP is used, where acknowledgement uses significant bandwidth along with original data packet.

UDP Header

Figure: Encapsulation of UDP Datagram

Above figure shows the encapsulation of a UDP datagram as an IP datagram.

Figure: UDP Datagram

Above figure shows the format of the UDP header. The port number identify the sending process and the receiving process.

Source Port: Source port number identifies the port of the sending application process.

Destination Port: Destination port number identifies the receiving process on the destination host machine.

UDP Length: The UDP length field is the length of the UDP data in bytes. The minimum value for this field is 8 bytes.

UDP Checksum: UDP checksum covers the UDP header and the UDP data. Both UDP and TCP include a pseudo-header with the UDP datagram just for the checksum calculations.

Data: Data field size is variable. It contains user data.

 

UDP Checksum Example

UDP checksum calculate from UDP header and UDP datagram part. Purpose of UDP header is check error in datagram. First of all, at sender side checksum has been calculated and checksum value added in checksum field. Again, checksum is calculated at receiver end, if there is mismatch in both the value, then datagram must be discarded by receiver, because no error recovery in UDP datagram. But in some of the application packet is pass to that application with warning. Here, below there is one example of UDP checksum.

Realtime application of UDP

Broadcasting and multicasting applications use UDP protocols.

Streaming media applications such as movies.

Online chatting and online multiplayer games.

Voice over IP (VoIP).

UDP is used with the RTOS (real time operating systems).

UDP is used in aircraft controls and flight instruments.

DNS uses UDP protocol, because immediate response is required in DNS.

Network layer protocols like RIP and UDP uses UDP because, it transfers very less amount of data.

Other protocols associated with UDP are Kerberos, Network Terminal Protocol (NTP), Network News Protocol (NNP) etc…

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