UDP

User Datagram Protocol (UDP) is a Transport Layer protocol. UDP is a part of the Internet Protocol suite, referred to as UDP/IP suite. Unlike TCP, it is an unreliable and connectionless protocol. So, there is no need to establish a connection prior to data transfer.

Though Transmission Control Protocol (TCP) is the dominant transport layer protocol used with most of the Internet services; it provides assured delivery, reliability and much more but all these services cost us with additional overhead and latency.

1. Source Port: Source Port is 2 Byte long field used to identify a port number of the source.
2. Destination Port: It is 2 Byte long field, used to identify the port of the destined packet.
3. Length: Length is the length of UDP including the header and the data. It is a 16-bits field.
4. Checksum: Checksum is 2 Bytes long field. It is the 16-bit one’s complement of the one’s complement sum of the UDP header, the pseudo header of information from the IP header and the data, padded with zero octets at the end (if necessary) to make a multiple of two octets.

Notes – Unlike TCP, the Checksum calculation is not mandatory in UDP. No Error control or flow control is provided by UDP. Hence UDP depends on IP and ICMP for error reporting.

Applications of UDP:

• Used for simple request-response communication when the size of data is less and hence there is lesser concern about flow and error control.

• It is a suitable protocol for multicasting as UDP supports packet switching.

• UDP is used for some routing update protocols like RIP(Routing Information Protocol).

• Normally used for real-time applications that can not tolerate uneven delays between sections of a received message.

• Following implementations uses UDP as a transport layer protocol:

• NTP (Network Time Protocol)

• DNS (Domain Name Service)

• BOOTP, DHCP.

• NNP (Network News Protocol)

• Quote of the day protocol

• TFTP, RTSP, RIP, OSPF.

• The application layer can do some of the tasks through UDP-
• Trace Route

• Record Route

• Timestamp

• UDP takes datagram from Network Layer, attaches its header and sends it to the user. So, it works fast.
• Actually, UDP is the null protocol if you remove the checksum field.