Practical_modern_SCADA_protocols_-_dnp3,_60870-5_and_Related_Systems

Appendix D: Practicals 509
E2 81 00 00 50< Application Data Read response AC Fir:1 Fin:1 Con:1 Seq:02 [IIN
Clear] [IIN Clear]
Object 80 01 00 00 0F 00< [IIN Clear] 00< [IIN
Clear] crc:E9 crc:8E —>
Setting The Time on the Slave:
Set Time Request 170 to 2
[ 15:13:3] 05 64 12 C4 02 00 AA 00<
Data Link Header [DIR] [PRM]
User Data (No Confirm) Length 18 Dest 2 Source 170 crc:40 crc:44
C4< Transport Header Fin:1, Fir:1, Seq:04
C4 02 32< Application Data Set Time request AC Fir:1 Fin:1 Con:0 Seq:04 Object 50
01 07 01
05 B7 05 A4 E8 00 crc:2B crc:B7
DNP3 Protocol Packet Analysis
Objective:
This information and practical is intended to provide the delegate with a practical understanding
of the DNP3 packet by providing information specific to packet interpretation.
Introduction:
DNP3 packets use hexadecimal as a language. Sometimes these hex values need to be
converted to decimal or binary values. The number of bytes in a datagram is an example
of a value in a DNP3 packet that needs to be changed. In the packet, the length value is
given in hexadecimal but we count in decimal, therefore the length needs to be converted
to decimal. Sometimes binary data is needed as in the flag settings within the Application
Layer portion of a packet. The eight bit hexadecimal values that represent the flag will
need to be converted into binary. Another part of the structure of the packet is the positioning
of the most significant and least significant bytes within two bytes of data. When
data needs to be represented by two bytes, such as an address, the least significant byte is
placed first and the most significant byte is place second. An example of this is…
Address – AA00 Hex (as shown in the data stream)
Address – 00AA Hex (as normally written, least significant byte first)
Address – 170 Decimal (after converting to decimal)
Or