Solved Incoming calls with no audio

[yogasensai]

Hello we are getting occasional incoming calls with no audio. Some days it doesn't happen and other days its more frequent. What do I need to check to fix this?



Firewall test results:



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starting service.. done

 

[Alphabetic]

How are the phones provisioned.

 

[yogasensai]

3cx app softphone. I have 4 sip trunks.

 

[Alphabetic]

Are you using a support SIP trunk?

 

[yogasensai]

I believe its unsupported.

TPG sip trunk.

Reading online suggests they only support G.711 A-Law audio codec. I have now deleted the other codecs in options

 

[yogasensai]

So the problem is still occuring. Its only happening on 2 different sites with Windows 11. We have a third site with Windows 10 and it has never happened.

I did get audio to work on a call by pressing the Windows media play pause key. But I haven't experimented enough to know if this is a real solution.

What do I need to do to investigate this further? I have seen some people using wireshark to track diagnostic information for calls should I try something like this?

 

[yogasensai]

I found an error using wireshark:

No | Time | Source | Destination | Protocol | Length | Info
1 0.000000 192.100.63.14 52.142.76.111 TLSv1.2 137 Application Data
2 0.000058 192.100.63.14 52.142.76.111 TLSv1.2 1528 Application Data
3 0.013394 52.142.76.111 192.100.63.14 TLSv1.2 96 Application Data
4 0.015852 52.142.76.111 192.100.63.14 TLSv1.2 104 Application Data
5 0.015852 52.142.76.111 192.100.63.14 TLSv1.2 795 Application Data
6 0.015852 52.142.76.111 192.100.63.14 TLSv1.2 92 Application Data
7 0.015909 192.100.63.14 52.142.76.111 TCP 54 49187 → 443 [ACK] Seq=1558 Ack=822 Win=1023 Len=0
8 0.109102 52.142.76.111 192.100.63.14 TLSv1.2 227 Application Data
9 0.155544 52.142.76.111 192.100.63.14 TLSv1.2 104 Application Data
10 0.278201 52.142.76.111 192.100.63.14 TCP 104 [TCP Retransmission] 443 → 62488 [PSH, ACK] Seq=224 Ack=1 Win=482 Len=50
11 0.546189 52.142.76.111 192.100.63.14 TCP 327 [TCP Retransmission] 443 → 62488 [PSH, ACK] Seq=1 Ack=1 Win=482 Len=273
12 2.146222 52.142.76.111 192.100.63.14 TCP 327 [TCP Retransmission] 443 → 62488 [PSH, ACK] Seq=1 Ack=1 Win=482 Len=273
13 2.146239 192.100.63.14 52.142.76.111 TCP 66 62488 → 443 [ACK] Seq=1 Ack=274 Win=1025 Len=0 SLE=1 SRE=274
14 6.331204 52.142.76.111 192.100.63.14 TLSv1.2 120 Application Data
15 6.372520 192.100.63.14 52.142.76.111 TCP 54 62488 → 443 [ACK] Seq=1 Ack=340 Win=1025 Len=0

Wire shark says the problem is [TCP Retransmission] but everywhere I read online says the problem could be anything

Windows Defender firewall settings looked a bit messy so I have deleted them all and made them the same as this working example:


I hope its as simple as windows defender blocking it...

 

[yogasensai]

I'm still getting the same problem even after changing windows firewall settings

17 0.220810 52.142.76.111 192.100.63.14 TCP 104 [TCP Retransmission] 443 → 55259 [PSH, ACK] Seq=224 Ack=1 Win=482 Len=50
18 0.496881 52.142.76.111 192.100.63.14 TCP 327 [TCP Retransmission] 443 → 55259 [PSH, ACK] Seq=1 Ack=1 Win=482 Len=273
19 1.000007 Microsof_2d:5e:01 Spanning-tree-(for-bridges)_00 LLDP 67 LA/DESKTOP-J8BA92C MA/00:2d:5e:01:af:0f 3601
20 1.040878 52.142.76.111 192.100.63.14 TCP 327 [TCP Retransmission] 443 → 55259 [PSH, ACK] Seq=1 Ack=1 Win=482 Len=273

There is a post here (https://www.3cx.com/community/threads/audio-drops-pause-for-user-s-part-4.85378/#post-401267)
saying:

[TCP Retransmission] usually means that you have packet loss (so it was retransmitted because no ack). It jives with garbled audio, out of sync audio, audio "catching up", etc.

Try a continuous ping from the affected machine to the 3CX server. Are you dropping packets?
Also one to the AP, to the router, and to some site externally. Depending on what drops you will learn it's AP, it inside the network, it's internet specific, etc.

Anybody know how to do a "continuous ping"?

I tried ping <server IP address or hostname> -t

but only got:

Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.

The problem seems to only be happening from 1 out of 3 DID softphones now.​

 

[yogasensai]

We upgraded our Windows 10 pc which has never had this problem to Windows 11 and its now had its first incoming call with no audio.

This pc is in a different state to the other one having problems.

wireshark:

27 0.149012 pbx pc TLSv1.2 104 [TCP Previous segment not captured] , Application Data
28 0.149038 pc pbx TCP 66 [TCP Dup ACK 22#1] 49245 → 443 [ACK] Seq=1 Ack=51 Win=1024 Len=0 SLE=222 SRE=272
29 0.150795 pbx pc TCP 225 [TCP Out-Of-Order] 443 → 49245 [PSH, ACK] Seq=51 Ack=1 Win=482 Len=171

Anyone know if 3cx has a good troubleshooting guide? Seems like they don't use this forum....


I'm going to start experimenting with any settings I can find. Changed the SIP Transport from UDP to TCP...

Waiting game now.

 

[Alphabetic]

Dont start changing settings without knowing what it does otherwise you'll end up chasing your tail and could introduce more problems.

Start with basic troubleshooting.

a) is PBX spec sufficient
b) does firewall test pass
c) can I replicate this issue making internal calls and echo test? *777
d) does this only happen on external calls?

If it only happens when calls are over your SIP provider you then need to perform additional tests. You must test until you can replicate.

a) does this happen when using the 3CX mobile app?
b) What is the symptom? One way audio or loss of audio both ways?
c) Turn on call recording, can you hear anything when you play back?
d) wireshark capture a problem call and review

Basically, the first thing id be doing is trying to replicate the issue and then seeing if it happens on the mobile app.

 

[yogasensai]

Start with basic troubleshooting.

a) is PBX spec sufficient 3cx AWS install
b) does firewall test pass Yes (1st post)
c) can I replicate this issue making internal calls and echo test? *777 Yes works fine
d) does this only happen on external calls? Yes (we don't use internal)

If it only happens when calls are over your SIP provider you then need to perform additional tests. You must test until you can replicate.

a) does this happen when using the 3CX mobile app? No
b) What is the symptom? One way audio or loss of audio both ways? Both (until we forward call to another extension)
c) Turn on call recording, can you hear anything when you play back? Not available
d) wireshark capture a problem call and review Posted above

Basically, the first thing id be doing is trying to replicate the issue and then seeing if it happens on the mobile app.

We have been using the webclient and do not get this issue. Problem seems to be Windows app only

 

[Lee Cramman]

Does ticking "PBX delivers audio" in SIP trunk make any difference?

 

[JohnS_3CX]

Just keep in mind that the firewall checker tests the first and last ports, not the whole audio range.

So in case the entire range is not forwarded correctly, when the ports eventually increment enough to reach the ones that are blocked, you will have audio issues. People who usually face this tend to mention that restarting the services temporarily fixes this (since the RTP range resets from the beginning).

- Do you have the issue only on external calls via Trunk or is it also affecting internal calls?
- What is your app version number?
- What is your PBX version number?

 

[yogasensai]

Does ticking "PBX delivers audio" in SIP trunk make any difference?

It was originally ticked. We have unticked it but haven't noticed a difference.

 

[yogasensai]

Just keep in mind that the firewall checker tests the first and last ports, not the whole audio range.

So in case the entire range is not forwarded correctly, when the ports eventually increment enough to reach the ones that are blocked, you will have audio issues. People who usually face this tend to mention that restarting the services temporarily fixes this (since the RTP range resets from the beginning).

- Do you have the issue only on external calls via Trunk or is it also affecting internal calls?
- What is your app version number?
- What is your PBX version number?

- Do you have the issue only on external calls via Trunk or is it also affecting internal calls? We don't make internal calls but will start testing that
- What is your app version number?
3CX Desktop App
Version:18.12.425
- What is your PBX version number?
18.0 (Build 312)

Just keep in mind that the firewall checker tests the first and last ports, not the whole audio range.

So in my first post i have firewall results. Does that mean the audio ports are:

testing ports [9000..9398]?
testing ports [10600..10998]?

In my wireshark log posted above, is the phone call trying to use port 62488? If its 62488 does that mean its above my port range?

How can I do a better test then? In 3cx Dashboard there is a 'Terminal' button which opens console. Should I use that?

I am using AWS to host 3CX

 

[JohnS_3CX]

So in my first post i have firewall results. Does that mean the audio ports are:

testing ports [9000..9398]?
testing ports [10600..10998]?

The audio ports are 9000-109999 and you should only open them on the AWS side (not on your PCs).
If you deployed it automatically in AWS via 3CX then we already opened the ports for you and you do not need to touch anything at all.

In my wireshark log posted above, is the phone call trying to use port 62488? If its 62488 does that mean its above my port range?

This might get confusing but I promise it's simple:

• The server talks and listens via 9000-109999
• The clients can talk and listen from any random TCP port - this is perfectly normal so don't worry about it.
• They don't both have to be on the same range, ports work independently of each other.
• Think of it like neighbors on two buildings: I can shout from my first floor, and you can shout from your 3rd floor and we can still talk to each other just fine.

No what we don't know is if you have internet connectivity issues between the PC and and the AWS server, causing your issues or if your trunk provider has issues. Some TCP retransmissions will not lead to any noticeable problems, but too many retransmissions often indicate that you have a network issue (ie. the data is not flowing, and you will notice audio problems for sure). More typical on WiFi, so do whatever you need to do to ensure a stable connection on the PC.

My guess is that you simply have an unstable internet connection and from time to time you lose audio. If you enable recordings in 3CX you can quickly find out by listening to the recording

- If the other side sounds well in the recording, but you couldn't hear them, then the connection between 3CX and your PC is the issue.

- If you hear yourself fine in the recording, but cannot hear the other side, then the connection between 3CX and provider is the issue.

 

[yogasensai]

My guess is that you simply have an unstable internet connection and from time to time you lose audio.

We don't have unstable internet. We have tried different lan cables, ports

We don't have problems with any other internet service.

Its only happening at one of our locations on a Windows 11 desktop app.

It does not happen on the same computer using 3cx webbrowser version in google chrome

We have never had a problem making outbound calls from this computer

It only happens on inbound calls. Some weeks its fine other weeks its really bad.

Whats making it difficult for me to diagnosis is that I really can't find a clear path to troubleshoot this.

We do see the error being captured in wireshark as posted above.

Currently the only solution we have is if we answer a call with no audio then we forward it to another extension.

Does 3cx have better troubleshooting information? I'm really keen to test all points of failure starting with the windows 11 pc, the 3cx server and the SIP provider

 

[Alejandro_3CX]

Hi @yogasensai as you mentioned this issue is only with the external calls and not with the internal calls, I suggest you to test with a supported VoIP Provider and let us know if experience the same issue or not.

Otherwise, if you want to keep the unsupported sip trunk you will need to contact them for troubleshooting their trunks.

 

[YiannisH_3CX]

It only happens on inbound calls. Some weeks its fine other weeks its really bad.

Whats making it difficult for me to diagnosis is that I really can't find a clear path to troubleshoot this.

We do see the error being captured in wireshark as posted above.

Currently the only solution we have is if we answer a call with no audio then we forward it to another extension.

Does 3cx have better troubleshooting information? I'm really keen to test all points of failure starting with the windows 11 pc, the 3cx server and the SIP provider

Here you go: https://www.3cx.com/3cxacademy/advanced/

In my opinion the best way to go about this is to hire a partner to help you troubleshoot. Alternatively you will need to keep a tshark capture running and once the issue occurs troubleshoot using the capture.
The errors you are seeing above don't really tell us anything as that could be anything especially out of context. You will need to see the SIP messages, check that the RTP ports used are correct and move from there. Then you can export the audio in both directions and see if audio is indeed present.

 

[yogasensai]

I am reporting that the issue has been solved.

We updated to V20 and now the problem is gone. One thing that could of been the cause was that V20 forced us to upgrade our hardware minimum requirements which was easy to do because we are using AWS.