Dialogic 6.2 - Manual (Page 104)

BSMI Debugging
November 2009 104
Understanding Trace Hexadecimal Strings
The hexadecimal string displayed in the trace consists of the
following components:
„ Information (I) Frame header
Note:
A trace displays hexadecimal strings for I Frame messages
only. Supervisory (S Frame) messages, such as Receiver Ready
(RR), and Unnumbered (U Frame) messages, such as SABME
and UA, are not displayed in hexadecimal format.
„ Message header
„ Information Elements (IEs)
Interpreting the I Frame Header
The I Frame header contains Layer 2 routing and packet transaction
information. The first four bytes of the hexadecimal string comprise
the I Frame header.
Figure 6 compares the general format for an I Frame against the I
Frame for an example SETUP message, and illustrates the following
points:
„ The trace automatically removes the 0x7E byte flags (binary
01111110) that normally indicate the start and end of the frame
and the Frame Check Sequence (FCS) values.
„ A trace automatically interprets and displays I Frame header
elements such as the SAPI and TEI (refer to Table 2 for
descriptions of these elements).
„ A value of 0 in the shaded bit position identifies the frame as an
I Frame.
00C10000 08010105040288901801812C0735353532303030
I Frame
03 278D Xmit 00 60 0 Setup 00 00 0 0018
Header