Gamma Trunk audio cutting off

Hi all,

I don’t have much to go on at the moment but posting this more to do with putting the feelers out to see if anyone else has experienced something similar.

We are experiencing random call disconnects always around the 15 minute mark. Calls are always outbound (inbound are still coming in via ISDN). Users are not that forthcoming at telling us they’ve been cut off but one person does which is handy

Absolutely nothing in the logs to signify a call disconnect.

The calls themselves don’t actually disconnect completely but we loose audio both ways.

I’ve spoken to Gamma UK (through our supplier) and they have came back with;

‘We are seeing what appears to be an anomaly in a stop signal being sent when the call hits 15 minutes. We have been unable to locate it in any other calls.’

I’ve asked them some more questions and waiting to hear back but in the meantime does this scenario mean anything to anyone or is there anything I can do this end (increase logging perhaps?) to try and trace it back?

Would anything firewall related cause this ‘stop’ signal or would this be a system trigger?

I’m running FPBX 16 Asterisk 18

Any help/advice appreciated and apologies for being vague

To prevent calls from staying up indefinitely in case of a network failure, a trunking provider typically sends a re-invite or UPDATE request every 15 minutes, dropping the call if the PBX does not respond properly.

Your problem occurs most commonly when the PBX is behind a NAT router/firewall and the NAT association has timed out so the re-invite does not reach the PBX.

Do all calls that last more than 15 minutes drop? If not, do you also see drops at 30 minutes, 45 minutes, etc.? Can you replicate the problem (if you call your mobile, does it drop after 15 minutes)? If so, call your mobile and hang it up after approximately 13 minutes. The calling phone should show the disconnect within a second or two. If not, you are losing the NAT association. Possible fixes for that include a short value for Expiration, e.g. 120 seconds, or a short Qualify Frequency, e.g. 60 seconds.

If the above is inapplicable or does not help, please post: Can you cause the trouble at will? If not, approximate percentage of calls that drop after 15 minutes? ISP? Modem make/model? Separate router/firewall, if any? VoIP-specific settings? Does trunk use registration? Do you have more than one trunk registered to the same Gamma server? If so, why?

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