Yealink T29G behaves like half duplex on outbound calls

[Jim Taylor]

We have a Debian 3CX instance running as a VM on a Windows Server running Hyper-V. We have a client site with a SBC and 7 Yealink T29G phones.
The call quality is fine, but if someone is speaking on one of the Yealinks, if the other (remote) party starts to talk back while the person is still speaking,
the remote party can't hear what the person had just said, almost as if it was half-duplex. While on the Yealink though, when speaking to a remote party,
if the remote party is speaking and you decide to start talking, you hear everything the remote party had said, but they never heard what you had said.
It seems one direction only where this is a problem. We verified that the router, SBC, and phones are all full duplex. If both parties don't talk over each other,
the call quality is fine otherwise. If they talk over each other, the remote party never hears what the 3cx/Yealink caller is saying. Any help is appreciated!

 

[AWS2P]

do you have Pbx deliver audio checked on SBC extensions?
Do you use same audio codec in same order on all extensions and trunk?

Phone firmware up to date?

 

[Jim Taylor]

On the latest build of 3CX, just updated to the newest release today.
PBX delivers audio is not checked.
Same audio codec in same order on all extensions and trunk.
Updated firmware on all devices today as well.

 

[BrenttG]

I cannot guarantee this, but i have seen extremely unusual networking behavior, not like this exactly, but definitely in the ball park from HyperV servers in the past, so much so, that we refuse to build 3CX servers on top of HyperV. We will do them on hardware, or hosted, but if its on hardware its either native on the hardware or on top of vmware, never hyperv.... My experience with such strange network issues on hyperv is not limited to the voip category either.... This goes double if its a HyperV clustered instance. For hosted instances, we use vmware exclusively and it works flawlessly with over 100 PBXs in the same cluster.

 

[JohnS_3CX]

Hi Jim,

Your description gives me the impression that the Yealink is being used in speakerphone mode.

If so, then yes that would make sense, while the other party is talking you have to remain silent because your mic gets "muted" to reduce feedback. Im curious if this is the case.

If not, I'm curious if you have this issue with other models too.

 

[Jim Taylor]

I've tried both hands free and with using the handset, same result. I will try a different brand of phone today and post the results. Interestingly enough, the 3cx iPhone client doesn't exhibit the behavior, so it doesn't appear to be a problem with Hyper-V on the surface; seems more like something with the handset itself.

 

[JohnS_3CX]

Hi Jim,

Yes that makes sense, and you propose a good test. Try a different brand or a newer yealink in the T4x series if one is available to you.

 

[Jim Taylor]

So, I just configured a Grandstream GXP2140 I had lying around and it worked like a champ. Tried it on two different 3CX instances I had to be sure it wasn't a fluke. So, it's something to do with the Yealink phones. I'll keep digging, but if anyone else has any thoughts or suggestions, they're greatly appreciated!

 

[AWS2P]

have you set your GXP2140 using same codecs?

 

[Jim Taylor]

Same codecs.

 

[Jim Taylor]

Going to try to manually provision in case there is something messed up in the template.

 

[AWS2P]

is it possible to directly send FW file with tftp server out of 3CX?

 

[Jim Taylor]

Ok, just got strange...manually provisioned and the problem is gone. Got a second unit and configured using auto provision and it worked without issue. So I think maybe it's hardware related. Take the 'bad' phone, factory reset, then let it autoprovision again and now it works. This is driving me nuts! Maybe it is intermittent and has a problem with Hyper-V like BrenttG wrote above. At this point, the service is working as expected and if it surfaces again, I'll spin up a VMWare instance and see how that behaves and will note any differences. Thanks for everyone's feedback.

 

[AWS2P]

were the phones completly powered off before your last tries ?

 

[Jim Taylor]

Yes, I've been unplugging, moving things around, trying different hardware, factory resetting, etc.

 

[AWS2P]

Perhaps this is the reason why it works now, phone have been out of remanant settings, and perhaps on 3cx side you've been also forgotten, then when you plug the phones 3CX see them as fresh ones and everything goes well

 

[Jim Taylor]

After more testing, it appears to be affecting calls to cell phones. When the problem just resurfaced, I called both a cell and a landline, and the landline was fine while the cell cut off.

 

[JohnS_3CX]

Alright Jim, I reckon you should just do a capture because the results you are getting are highly inconsistent.

The correct question to ask is: are you sending out the audio to the provider when the issue occurs?

If so, then you can forget about the Yealinks, the SBC and the VM altogether and skip the whole run around