Filter
Top Products
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