Understanding ISO 8583 messaging log

Question

I read about ISO 8583 messaging at WIKI and Code Project; I understood ISO 8583 messages can basically be divided in 3 parts:

1. MTI (Message Type Indicator)

Answer 1

Got it,
This message is divided as follows:

First 2 bytes are the message length 00 5B = 91
Followed by 14 bytes of header = 01100000000820

Followed somehow by BMP as follows:

• Primary BMP = 80 38 00 00 00 81 00 00 = Fields {1, 11,12, 13, 41, 48} exist
  Field 1 means secondary BMP exist
• Secondary BMP = 04 00 00 00 00 00 00 00 = Field 70 exist

I am not sure where is MTI, will it be the 0820 at the trailer of the header? since it is in ASCII and usually it comes in numeric value of 08 20 but this might be part of the specs. 0820 means network management advice

anyways, the fields from the decoded BMP as follows:

• DE 11 = 362910
  System Trace Audit Number
• DE 12 = 102957
  Local transaction time hh(24)mmss
• DE 13 = 1031
  Local transaction date MMDD
• DE 41 = 10000005
  terminal ID
• DE 48 = (031) SU20111031102957201110311029573
  notice the 3 digits length field preceding the remaining data in this field. which is a generic (future/private use) field
• DE 70 = 001
  network management information code <001 = sign on>

From DE 70 value 001 this is a sign on message, which must be a 0800 MTI.

To get more information about the location of the MTI and the meaning of DE 48, you should read the manual (technical specs) of this device to get more information.