Solved Incoming Call via Vol LTE

[George Stavrianos]

Hello,

we found that when someone calls our center and has Vol LTE activated on their cell phone, the line drops. But if the Vol LTE function is disabled, then the call will be made normally. The provider told us that some setting has to be done inside the center for Vol LTE calls.

Do you know what can we do for this problem?

Thanks

 

[JohnS_3CX]

Hi George,

I think is a technical question that should be directed to your provider first and foremost.

Once they give you feedback on what they want changed, we can then tell you whether there is a setting in 3CX that controls that specific thing.

Ask them what needs to be changed in the SIP messages. If they cannot give you a solid answer then maybe it's better to contact a 3CX Partner and have them analyze the traffic. They will at least be able to tell you whatever the provider is doing which leads to calls being dropped.

 

[George Stavrianos]

Hello John,

thanks for your quick reply, i would contact with our provider and will inform you

 

[George Stavrianos]

Hello,
my provider is contacted with me and told me to remove the phone context to field "to".

How can i do this?

Thanks

 

[George Stavrianos]

Hello again, I provide you with the 2 different SIP messages with susccesfull dial (without Vol LTE) and unsuccesfull dial (with Vol LTE), as the provider sent to us

1) Successful call:
To: <sip:[email protected];user=phone>

2) Unsuccessful call :
To: <sip:XXXXXXXXXX;phone-context=ims.mnc010.mcc202.3gppnetwork.org@ims.mnc010.mcc202.3gppnetwork.org;user=phone>

So they informed me that we must be remove the phone-context to unsuccessful call.

How can i do this or something else to solve the problem?

Thanks a lot

 

[YiannisH_3CX]

I am not sure how this is a 3CX issue. You are referring to inbound calls towards the PBX and these changes should be made from the VoLTE (mobile) carrier as far as I understand.

 

[JohnS_3CX]

You can switch to a supported provider: https://www.3cx.com/partners/sip-trunks/greece/

 

[George Stavrianos]

Hi Yannis,

thank you very much for your quick response. Do you think that there is nothing to do on 3CX PBX to solve the problem, because we are referring for outbound calls and probably is provider problem, correctly?

Also I would like to inform you that from the other provides of Greece does not exist the same problem, and working normally with VoLTE.

Thanks you again

 

[YiannisH_3CX]

The values you are referencing are not sent by 3CX. We do not use these values so this is an issue between your SIP provider and the VoLTE carrier.
As my colleague suggested its best to switch to a 3CX supported provider where we can provide more assistance.

 

[George Stavrianos]

Thanks again, I informed my provider for all of these, but I contacted with you to confirm.

Also they will call me again, therefore if is there something else I will inform you.

Thanks a lot

 

[George Stavrianos]

Hello again.
My provider contacted with me and they told me that there is a setting from the PBX to avoid the phone context and if adjust it then the call from VoLTE will work fine.

Is this correct or no?

Thanks

 

[YiannisH_3CX]

2) Unsuccessful call :
To: <sip:XXXXXXXXXX;phone-context=ims.mnc010.mcc202.3gppnetwork.org@ims.mnc010.mcc202.3gppnetwork.org;user=phone>

So this is what arrives at the PBX when calls originate from VoLTE?

If that is the case then I can see why the call drops. The To header is invalid.
Based on what else in the Invite coming from the provider you could set the PBX to read the called number from a different SIP header from the trunks inbound parameters. However this will affect all calls and if the called number is not present anywhere else in the Invite then you will not have call routing.
So its really up to you to look at the Invite coming from the provider and determine what the best settings are. And we cannot guarantee this will work either.
The other option is to go back to your provider and ask why they are forwarding invalid SIP headers. They should be reformatting these requests to a SIP compatible format.
Your best choice however still is to use a supported provider.

 

[George Stavrianos]

Yes correctly , that is the case.
My provider informed me, to try to change the header To and if this not solve the problem, so they investigate from their side.
How can we change the header To, to read the called number from a different SIP header, as you can told me?

Which are the steps which I can follow?

Thank you

 

[George Stavrianos]

I think that i find the solution. I changed the header To to the value "Request Line URI :user part" as below :

"CalledNum" number that has been dialed (default: To->user) -----------> "Request Line URI :user part".

After this change the call via VoLTE is not dropped.

Thanks for your important and quickly responses to my threads.