No Ringing on some external calls

[anthony0030]

I am running the latest firmware 18.0 (Build 314) on my server that is running on a raspberry pi locally.
The firewall tests pass with no problems.
I am using a Cosmote internet line with its SIP trunk.

I sometimes don't hear the ringing sound when calling an external number. I did some packet captures and figured out that when a 180 is sent the phone rings.
When a 180 and a 183 is sent the phone doesn't ring and after some time I am connected to the other side with 2-way audio.
I noticed that when a 183 is sent a RTP stream opens with a faint hissing sound and no ringing.
If I phone an incorrect phone number I get the same 180 183 but I hear a message from my ISP telling me that the number I enterd is incorrect.

When I set ENABLEEARLYMEDIA to 0 I always get ringing even if the number is incorrect. is there a way to have both ringing and early media?

 

[YiannisH_3CX]

Hi @anthony0030

In what order are these messages sent? Do you get the 180 first followed by the 183 or the other way around? Also is there an SDP in the 183 message?

 

[anthony0030]

First I get a 100 trying I get a one or two 183s then I get a 180 then I get a 200.
The protocol is SIP/SDP.
I think I have narrowed it down to one cell provider. COSMOTE MOBILE.
They send an RTP with a hissing sound.
I phoned them and let them know.
But if they don't fix it is it possible to fix it with a setting in 3CX?

 

[YiannisH_3CX]

No you cannot change this in 3CX. If an 183 is received and then an 180 the 180 is ignored. But you should not get an 183 with SDP if there is nothing to be played by the provider. Hopefully Cosmote will be able to fix it from their side.

 

[anthony0030]

There is an RTP stream with hissing sounds. The provider offers music on ringing. so possibly if someone has music it will be played in that stream.
But if there is no music they should not send 183 with a black stream (Hissing stream). I will keep you posted in case someone has the same problem in the future. I have an ETA of today or latest tomorrow from the ISP.