USER DATAGRAM PROTOCOL (UDP) (see RFC 768)
User Datagram Protocol is utilized to send data that doesn't necessarily need to be very reliable. The UDP packet is encapsulated in an IP packet which in turn is encapsulated in a PPP packet. Both UDP and IP have checksums octets and the PPP packet has its FCS octets however this can only guarantee that the data and the destination are correct. However, there is a possibility that this data does not belong to an expected message sequence but is rather part of another message that just happened to have the same destination. This issue is addressed by the TCP protocol. UDP is a simple to implement protocol because it does not require to keep track of every packet sent or received and it does not need to initiate or end a transmission. Because of this it is mainly designed for communications where you either don't care what the response will be or you pretty much know it. UDP messages are generally faster than TCP provided that the communication link functions properly. UDP is widely utilized to send DNS (Domain Name Search) requests, to exchange chat messages, or to access telephone numbers via Internet.
UDP HEADER FORMAT OCTET 1,2 Source Port OCTET 3,4 Destination Port OCTET 5,6 Length OCTET 7,8 Checksum OCTET 9,10….. Data UDP PACKET (Example) 04 89 00 35 00 2C AB B4 00 01 01 00 00 01 00 00 00 00 00 00 04 70 6F 70 64 02 69 78 06 6E 65 74 63 6F 6D 03 63 6F 6D 00 00 01 00 01 UDP Header 04 89 00 35 00 2C AB B4 Data 00 01 01 00 00 01 00 00 00 00 00 00 04 70 6F 70 64 02 69 78 06 6E 65 74 63 6F 6D 03 63 6F 6D 00 00 01 00 01 Source Port 04 89 Destination Port 00 35 Length 00 2C Checksum AB B4 Data DNS Message
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