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ISDN Problem


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 ?



Re: ISDN Problem

It looks like the ISDN is not configured to allow data calls. If it is not configured for data calls, all calls (including data calls) are "clipped" to 56k. This is fine for voice calls, but for data calls it will garble the data packets.

Understanding debug isdn q931 Disconnect Cause Codes:

New Member

Re: ISDN Problem

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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