7 13). (9 points) The application service data unit (ASDU) is defined as following according to IEC60870-5101 protocol. Type identifier Data unit Variable structure qualifier Data unit type identifier Cause of Transmission Common address of ASDU Information object dress Information Information element set Information object identifier ASDU object 1 Time stamp with 3 or 7 Time stamp of information object bytes Information object address Information object identifier Information information element set object 2 Time stamp with 3 or 7 Time stamp of information object bytes 0. Explain the meanings of type identifier, variable structure qualifier, cause of Transmission, common address of ASDU and information object address? (3 points) An actual message is '68 OA OA 68 08 01 40 01 OC 01 01 30 81 00 09 16, please point out the type identifier, variable structure qualifier, cause of Transmission, common address of ASDU and information object address of this message. (2 points) 3) What is value of the check code? How do we calculate it? (4 points) o