User Datagram Protocol (UDP)

Sometimes it is more important that communications be faster than they are reliable
- connection-oriented process of TCP adds lots of header bytes to each packet

User Datagram Protocol (UDP) is a connectionless, non-guaranteed method of communication with no sequencing or acknowledgements.

works at the Transport layer
no guarantee regarding the:
- delivery of messages
- sequence in which packets are received
- mechanism for retransmitting lost or damaged packets
suitable for applications that:
- send small amounts of data in each packet
- do not require acknowledgement of receipt
- can tolerate missing or out-of-order packets
application layer or software logic can be used to control delivery reliability
uses:
- Application layer protocols that need to send multicast or broadcast traffic
- applications that transfer time-sensitive data but do not require complete reliability
  - e.g., voice or video
  - using small packets means that if a few are lost or arrive out of order, it results in only minor glitches
  - missing data manifests as glitches rather than application errors or complete connection failures
reduced overhead means that delivery is faster
header size is 8 bytes
structure of a UDP header:

Field	Explanation
Source port	UDP port of sending host.
Destination port	UDP port of destination host.
Message length	Size of the UDP packet.
Checksum	Ensures validity of the packet.

Examples