Manual browser: isdntrace(8)

ISDNTRACE(8) System Manager's Manual ISDNTRACE(8)


isdntraceisdn4bsd ISDN protocol trace utility


isdntrace [-a] [-b] [-d] [-f filename] [-h] [-i] [-l] [-n number] [-o] [-p filename] [-r] [-u number] [-x] [-B] [-F] [-P] [-R unit] [-T unit]


isdntrace is part of the isdn4bsd package and is used to provide the user with a mnemonic display of the layers 1, 2 and 3 protocol activities on the D channel and hex dump of the B channel(s) activities.

Together with two passive supported cards and an easy to build cable it can also be used to monitor the complete traffic on a S0 bus providing S0 bus analyzer features.

The isdntrace utility is only available for passive supported cards.


All filenames, user specified or default, get a date and time stamp string added in the form -yymmdd-hhmmss: a hyphen, two digits year, month, day, a hyphen and two digits hour, minutes and seconds. Trace files no longer get overwritten. In case a new filename is needed within a second, the filename-generating mechanism sleeps one second.
In case the program is sent a USR1 signal, a new user specified or default filename with a new date and time stamp is generated and opened.

The following options can be used:

Run isdntrace in analyzer mode by using two passive cards and a custom cable which can be build as described in the file cable.txt in the isdn4bsd source distribution. One card acts as a receiver for the transmitting direction on the S0 bus while the other card acts as a receiver for the receiving direction on the S0 bus. Complete traffic monitoring is possible using this setup.
switch B channel tracing on (default off).
switch D channel tracing off (default on).
Use filename as the name of a file into which to write tracing output (default filename is isdntrace<n> where n is the number of the unit to trace).
switch display of header off (default on).
print layer 1 (I.430) INFO signals to monitor layer 1 activity (default off).
switch displaying of Layer 2 (Q.921) frames off (default on).
This option takes a numeric argument specifying the minimum frame size in octets a frame must have to be displayed. (default 0)
switch off writing trace output to a file (default on).
Use filename as the name of a file used for the -B and -P options (default filename is isdntracebin<n> where n is the number of the unit to trace).
Switch off printing a raw hexadecimal dump of the packets preceding the decoded protocol information (default on).
Use number as the unit number of the controller card to trace (default 0).
Switch on printing of packets with a non-Q.931 protocol discriminator. (default off).
Write undecoded binary trace data to a file for later or remote analyzing (default off).
This option can only be used when option -P (playback from binary data file) is used. The -F option causes playback not to stop at end of file but rather to wait for additional data to be available from the input file.

This option is useful when trace data is accumulated in binary format (to save disk space) but a monitoring functionality is desired. (default off).

Read undecoded binary trace data from file instead from device (default off).
Use unit as the receiving interface unit number in analyze mode.
Use unit as the transmitting interface unit number in analyze mode.

When the USR1 signal is sent to a isdntrace process, the currently used logfiles are reopened, so that logfile rotation becomes possible.

The trace output should be obvious. It is very handy to have the following standard texts available when tracing ISDN protocols:

ISDN BRI layer 1 protocol description.
ISDN D-channel layer 2 protocol description.
ISDN D-channel layer 3 protocol description.
German-specific ISDN layer 3 protocol description. (NOTICE: decoding of the 1TR6 protocol is included but not supported since i dont have any longer access to a 1TR6 based ISDN installation.)

isdntrace automatically detects the layer 3 protocol being used by looking at the Protocol Discriminator (see: Q.931/1993 pp. 53).


The device file(s) used to get the trace messages for ISDN card unit <n> out of the kernel.


The command:

isdntrace -f /var/tmp/isdn.trace

will start D channel tracing on passive controller 0 with all except B channel tracing enabled and logs everything into the output file /var/tmp/isdn.trace-yymmdd-hhmmss (where yymmdd and hhmmss are replaced by the current date and time values).




ITU Recommendations I.430, Q.920, Q.921, Q.930, Q.931

FTZ Richtlinie 1TR3, Band III

ITU Recommendation Q.932 (03/93), Q.950 (03/93)

ETSI Recommendation ETS 300 179 (10/92), ETS 300 180 (10/92)

ETSI Recommendation ETS 300 181 (04/93), ETS 300 182 (04/93)

ITU Recommendation X.208, X.209


The isdntrace utility was written by Gary Jennejohn and Hellmuth Michaelis.

This manual page was written by Hellmuth Michaelis <>.

February 13, 2000 NetBSD 7.0