BSMI Debugging

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.

03 278D Xmit 00 60 0 Setup 00 00 0 0018

00C10000 08010105040288901801812C0735353532303030

IFrame 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.

November 2009

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Dialogic 6.2 manual Understanding Trace Hexadecimal Strings, Interpreting the I Frame Header, November 104