UDP protocol

Characteristics of the UDP protocol

The UDP protocol (User Datagram Protocol) is a connectionless orientated protocol of the transport layer of the TCP/IP model. This protocol is very simple given that it does not provide error detection (it is not connection orientated...).

The UDP segment header is therefore very simple:

Source port
(16 bits):
Destination port
(16 bits):
Total length
(16 bits)
Header checksum
(16 bits)
(variable length)

Meanings of the different fields

  • Source port: this is the port number relating to the originator application of the UDP segment. This field represents a response address for the recipient. So, this field is optional, which means that if the source port is not specified the 16 bits of this field will be set to zero, in which case the recipient will not be able to respond (this is not strictly necessary, in particular for one way messages).
  • Destination port: This field contains the port corresponding to the application on the recipient machine to which it is sent.
  • Length: This field specifies the total length of the segment, header included, however, the header has a length of 4 x 16 bits (which is 8x8 bits) so the field length is necessarily greater than or equal to 8 bytes.
  • Checksum: This is a checksum conducted in such a way as to be able to check the integrity of the segment.
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