C-10 IRAS-24A T1/ISDN Modem Card Installation and Reference Guide
Tracing Link Activity
The diagnostic trace function allows you to trace Layer 2 and
Layer 3 messages entering and leaving the HDLC controller
on the board. The trace function displays link layer protocol
messages only, such as ISDN Q.931. The trace display
resembles a simple protocol analyzer, with the message type
decoded and its direction shown.
Two types of traces are supported:
-
A Level 1 trace shows Layer 2 and Layer 3
messages being passed over the links, and
provides some protocol and routing information.
-
A Level 2 trace resembles a Level 1 trace but also
displays the received/transmitted message
Information frame in hexadecimal format. This
hexadecimal string contains Layer 2 and Layer 3
ISDN frame headers, as well as the complete
contents of the Layer 3 frame.
NOTE:
The transmit buffer for the serial diagnostic port is limited
to 4 K in size. If you start a link trace during a period of
high message traffic, the messages may wrap the buffer and
some messages may not be displayed.
Running a Level 1 Trace
To start a Level 1 trace, type
L 1
and press
Return
. To stop the
trace, type
L 0
and press
Return
. Values that appear during
the trace are defined in Table C-2. Figure C-5 shows an
example trace of an ISDN Q.931 call, from link establishment
to call release. The trace was run with the board’s spans
connected by a cross-over cable to show activity at both ends
of the connection.
Summary of Contents for IRAS-24A w/ T1-RBS
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