Integrated Services Digital Network

:ISDN is also short for isosorbide dinitrate

A sample ISDN call

The following is an example of a Primary Rate (PRI) ISDN call showing the Q.921/LAPD and the Q.931/Network message intermixed (i.e. exactly what was exchanged on the D-channel). The call is originating from the switch where the trace was taken and goes out to some other switch, possibly an end-office LEC, who terminates the call.

Related Topics:
Q.921 - LAPD - Q.931

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The first line format is <time> <D-channel> <Transmitted/Received> <LAPD/ISDN message ID>. If the message is an ISDN level message, then a decoding of the message is attempted showing the various Information Elements that make up the message. All ISDN messages are tagged with an ID number relative to the switch that started the call (local/remote). Following this optional decoding is a dump of the bytes of the message in <offset> <hex> ... <hex> <ascii> ... <ascii> format.

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The RR messages at the beginning prior to the call are the keep alive messages. Then you will see a SETUP message that starts the call. Each message is acknowledged by the other side with a RR.

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10:49:47.33 21/1/24 R RR

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0000 02 01 01 a5 ....

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10:49:47.34 21/1/24 T RR

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0000 02 01 01 b9 ....

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10:50:17.57 21/1/24 R RR

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0000 02 01 01 a5 ....

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10:50:17.58 21/1/24 T RR

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0000 02 01 01 b9 ....

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10:50:24.37 21/1/24 T SETUP

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Call Reference : 000062-local

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Bearer Capability : CCITT, Speech, Circuit mode, 64 kbit/s

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Channel ID : Implicit Interface ID implies current span, 21/1/5, Exclusive

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Calling Party Number : 8018023000 National number User-provided, not screened Presentation allowed

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Called Party Number : 3739120 Type: SUBSCRB

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0000 00 01 a4 b8 08 02 00 3e 05 04 03 80 90 a2 18 03 .......>........

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0010 a9 83 85 6c 0c 21 80 38 30 31 38 30 32 33 30 30 ...l.!.801802300

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0020 30 70 08 c1 33 37 33 39 31 32 30 0p..3739120

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10:50:24.37 21/1/24 R RR

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0000 00 01 01 a6 ....

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10:50:24.77 21/1/24 R CALL PROCEEDING

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Call Reference : 000062-local

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Channel ID : Implicit Interface ID implies current span, 21/1/5, Exclusive

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0000 02 01 b8 a6 08 02 80 3e 02 18 03 a9 83 85 .......>......

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10:50:24.77 21/1/24 T RR

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0000 02 01 01 ba ....

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10:50:25.02 21/1/24 R ALERTING

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Call Reference : 000062-local

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Progress Indicator : CCITT, Public network serving local user, In-band information or an appropriate pattern is now available

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0000 02 01 ba a6 08 02 80 3e 01 1e 02 82 88 .......>.....

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10:50:25.02 21/1/24 T RR

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0000 02 01 01 bc ....

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10:50:28.43 21/1/24 R CONNECT

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Call Reference : 000062-local

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0000 02 01 bc a6 08 02 80 3e 07 .......>.

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10:50:28.43 21/1/24 T RR

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0000 02 01 01 be ....

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10:50:28.43 21/1/24 T CONNECT_ACK

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Call Reference : 000062-local

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0000 00 01 a6 be 08 02 00 3e 0f .......>.

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10:50:28.44 21/1/24 R RR

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0000 00 01 01 a8 ....

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10:50:35.69 21/1/24 T DISCONNECT

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Call Reference : 000062-local

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Cause : 16, Normal call clearing.

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0000 00 01 a8 be 08 02 00 3e 45 08 02 8a 90 .......>E....

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10:50:35.70 21/1/24 R RR

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0000 00 01 01 aa ....

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10:50:36.98 21/1/24 R RELEASE

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Call Reference : 000062-local

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0000 02 01 be aa 08 02 80 3e 4d .......>M

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10:50:36.98 21/1/24 T RR

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0000 02 01 01 c0 ....

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10:50:36.99 21/1/24 T RELEASE COMPLETE

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Call Reference : 000062-local

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0000 00 01 aa c0 08 02 00 3e 5a .......>Z

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10:50:36.00 21/1/24 R RR

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0000 00 01 01 ac ....

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10:51:06.10 21/1/24 R RR

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0000 02 01 01 ad ....

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10:51:06.10 21/1/24 T RR

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0000 02 01 01 c1 ....

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10:51:36.37 21/1/24 R RR

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0000 02 01 01 ad ....

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10:51:36.37 21/1/24 T RR

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0000 02 01 01 c1 ....

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