ISDN Problem

Unanswered Question
May 4th, 2009


I have trouble with a 15 channel PRI E1/ISDN with calls from a london site to swiss mobile phones. The problem has been seen with this destination but may occur with some others.

It is a CCM 4.1.3 infrastructure, london is a remote site with a local h323 gateway 2800 series, 12.4.18 . pri-group 1-16 is configured (this may not be a problem of available channels).

Problem: 1 call out of two or three (not periodic) I described is failing: called party does not ring and calling party hears a constant tone.

In both cases the q931 setup is sent with the exact same syntax.

when it works: I receive alerting message, everything is ringing normally, and the call can be connected.

when it does not work: I receive a progress message , called party does not ring at all, and calling hears a constant tone.


*Mar 20 12:01:32.414: ISDN Se0/0/0:15 Q931: RX <- PROGRESS pd = 8

callref = 0xB


Progress Ind i = 0x8A81 - Call not end-to-end ISDN, may have

in-band info, - and then no inband info is coming, the trace stops)

When caller hangs up, a disconnect is sent (no connect is sent before).

I have played with every progress_ind paramter as well as voice call commands

voice call send-alert

voice call convert-discpi-to-prog

voice call carrier capacity active

voice rtp send-recv

with no success. Looking for an issue about ring back tone I don't have, which is a classic issue, it came to my mind that even if I had no ring back tone it was not my gateway responsability to make the caller party ring, which actually does not. Seems to be a provider issue. Any idea or suggestion ?


I have this problem too.
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m.schlienger Sun, 05/10/2009 - 23:15

Thank you for your message.

Unfortunately, as I described it concerns only voice calls, especially uk to swiss mobile phones (that's the case I observed and where the users are complaining). No ISDN data calls.

Disconnect cause has no error, since it sends a DISCONNECT only when calling party hangs up. But before that, no CONNECT occured, and it sticks to the PROGRESS message I mentioned.

Thanks for your help.



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