sporadic choppy audio for 23-30 seconds

[_NL]

Good day to all,

We have the problem that in some phone calls 20-30 seconds pass before the other side understands us.
Audio only reaches the other side in a very choppy and incomprehensible way.
The problem only occurs with outgoing calls.
However, the problem is only sporadic and cannot be traced from my side.
The problem does not occur with internal telephony.

3CX version: 18.0.1880
Server OS: Debian 10 Buster
On-Premise installation on a virtual machine
Only softphones used: Webclient 18.0.0.1880 and DesktopApp 18.3.33
Has the Firewall Checker passed: YES

Is the behavior known and are there any possible solutions for troubleshooting ?
I suspect it is not a 3CX problem.

 

[ChrisC_3CX]

Since it only affects outgoing calls it might indeed not be a 3CX Issue but there's a few things you can do to further confirm this.

• First off, what SIP Provider are you using, is it a 3CX Supported one?

• When you say Outgoing calls, do you mean external calls in general(incoming and outgoing) or only ones initiated from a 3CX extension to an external number and not the other way around?

• How frequently does this happen? I know you said it's sporadic, but can you reproduce the issue after making a reasonable number of attempts?

• Does the issue perhaps only happen with specific callers/callees?

• What Hypervisor is the VM running on?

 

[_NL]

We use Deutsche Telekom's NGN, so yes, that is supported.

I mean calls initiated from a 3cx extension.
Calls that we recieve does not affect this problem.

We have tested it within our team on an estimated 10 of our private numbers.
Unfortunately we could not reproduce it in our testing session.

The affected department often complains about these problems.

The issue can occur to every caller.
And it does not happen on every call with a specific callee.

 

[ChrisC_3CX]

The fact that this only affects outgoing calls and not incoming is a bit weird but it may mean that it is related to the codecs used as who initiates the call will matter for codec selection.

First I'd recommend making sure that you're using the default codecs and priority for this SIP Trunk
(Edit SIP Trunk >> Options):





Then, go into "Settings >> Codecs" and make sure that at least the first 2-3 codecs are the same to avoid transcoding.

You can try changing the codec order but remember to do it for both SIP Trunk and PBX so that they match.

Another thing I would suggest is making sure that the 3CX PBX at hand is not underspeced.

If you do not notice any improvements after doing the above you might need to look into this further by possibly analyzing packet captures to determine if the issue is indeed originating from the 3CX PBX or not. That said, if it does come to this, you might want to consider contacting one of our partners to get help with the investigation.