Silent Ring on Caller's Side

[John]

Hi everyone,

I recently have an issue with my FusionPBX/FreeSwitch. What happens is the calls ring silently on the caller's side. That is, it rings on my phone, but the caller is not hearing any ring. Just silence until I answer the call or it goes to voicemail. Many just give up thinking the line is disconnected. This is really terrible and happens everyday. The only solution is to go to Status > SIP Status and Flush Cache, Reload ACL, Reload XML, Refresh.

Then the issue disappears. Interestingly, even rebooting the server does not resolve the problem.

Anyone facing the same issue?

System Information​
Operating System Information​
Version	4.5.25
Git Information	Branch: master Commit: f97b0a7de745aad0d1b7c6abf1e41a1ac192fd27 Origin: https://github.com/fusionpbx/fusionpbx Status: Your branch is up to date with 'origin/master'. +1 days ago
Project Path	/var/www/fusionpbx
Switch Version	1.10.5 (64bit)
PHP Version	7.3.27-1~deb10u1
Operating System	Debian

 

[Adrian Fretwell]

We had something similar to this a few years ago, I can't remember all the detail right now but I'm sure it was to do with an endpoint not responding correctly to Early Media (183 Session Progress).

180 & 183 are just two different provisional responses; 180 is ringing and 183 is Session in Progress. 183 is normally associated with early media because the 183 response often has an SDP body attached so locally generated ringtone or a message can be played to the caller.

I'm trying to remember exactly, I think forcing 180 ringing solved the issue, thus causing the UAC to generate it's own ringing internally and I eventually proved that early media was actually being sent but it contained no ring tone, it was just a silent RTP stream. I will add to this post when I remember more about it, but hopefully this will give you something to consider in the mean time.

 

[John]

We had something similar to this a few years ago, I can't remember all the detail right now but I'm sure it was to do with an endpoint not responding correctly to Early Media (183 Session Progress).

180 & 183 are just two different provisional responses; 180 is ringing and 183 is Session in Progress. 183 is normally associated with early media because the 183 response often has an SDP body attached so locally generated ringtone or a message can be played to the caller.

I'm trying to remember exactly, I think forcing 180 ringing solved the issue, thus causing the UAC to generate it's own ringing internally and I eventually proved that early media was actually being sent but it contained no ring tone, it was just a silent RTP stream. I will add to this post when I remember more about it, but hopefully this will give you something to consider in the mean time.

Adrian,

Thank you very much for doing your best to help as always. Yes. I would appreciate more information on this. Also, how did you force 180 ringing?

Sincerely,

J

 

[Adrian Fretwell]

John, I have had a good look back through my notes and have not come up with anything that will definitely help you, but I'm pretty sure this does all revolve around early media.

When a phone receives a 180 ringing, without SDP, it will generate ringing tone (ringback) locally. When a phone receives a 183 with SDP, it will receive and playback whatever the far end is sending. If the far end is sending nothing or the RTP stream is blocked by firewall or NAT, then you hear nothing.

The issue I was remembering was with a customers SonicWall firewall, I can't double check this because they no longer have the SonicWall. But according to my notes it was blocking 183 SIP messages but not 180 SIP messages. It was a policy focused on SIP Session Progress messages and what it called Low Priority Attacks.

You are probably going to need to do some packet capturing to find out exactly what is going on. In my case it was network related.

 

[John]

John, I have had a good look back through my notes and have not come up with anything that will definitely help you, but I'm pretty sure this does all revolve around early media.

When a phone receives a 180 ringing, without SDP, it will generate ringing tone (ringback) locally. When a phone receives a 183 with SDP, it will receive and playback whatever the far end is sending. If the far end is sending nothing or the RTP stream is blocked by firewall or NAT, then you hear nothing.

The issue I was remembering was with a customers SonicWall firewall, I can't double check this because they no longer have the SonicWall. But according to my notes it was blocking 183 SIP messages but not 180 SIP messages. It was a policy focused on SIP Session Progress messages and what it called Low Priority Attacks.

You are probably going to need to do some packet capturing to find out exactly what is going on. In my case it was network related.

Adrian,

Thank you very much for the detailed explanation. I will do some tracing and see what is going on. However, I have some updates on this issue, which I would like to share. I can now fully reproduce the problem.

My server reboots every night to get a full image copy. Simply it happens after each reboot. What really fixes the issue is Reloading the ACL. For now, I will add a crone task to reload the ACL after each reboot (will find out how to). Then will investigate further what is happening using sngrep.

It is great to have you here.

Sincerely,

J

 

[Adrian Fretwell]

John, the command to reload ACL from cron would be fs_cli -x "reloadacl" but I don't understand why this solves the issue. When the server reboots and FreeSWITCH starts up it would load it's ACL then. Unless maybe there is a timing/dependency issue with PostgreSQL not being ready?

Do you need to reboot to get an image copy, I only ask because we don't, having said that I only image the disks not the memory.

 

[John]

John, the command to reload ACL from cron would be fs_cli -x "reloadacl" but I don't understand why this solves the issue. When the server reboots and FreeSWITCH starts up it would load it's ACL then. Unless maybe there is a timing/dependency issue with PostgreSQL not being ready?

Do you need to reboot to get an image copy, I only ask because we don't, having said that I only image the disks not the memory.

Adrian,

You are right. Reloading ACL on reboot does not solve the issue, as FreeSwtich is already doing that. I scheduled the reaload ACL-- by the way thanks for saving me time on finding the right crone command--few minutes after the reboot.

I also do not understand why reload ACL solves the issue, but thank God it does : )

About the image copy, my VPS manager (I have FreeSwitch on a VPS inside my dedicated server) guide says backups created with Stop instead of suspend, are guaranteed to work on other servers but backups with suspend are not guaranteed to work.

By the way, how can I subscribe to help posts, so I can also help others within the limit of my knowledge.

Sincerely,

J

 

[Adrian Fretwell]

I'm sorry, I'm not sure what you mean by "subscribe to help posts". I just click on the "Whats new" tab, and any post that hasn't been answered, I try to provide some help. I normally leave unanswered posts a day before responding unless I absolutely know what the answer is. There are a lot of very knowledgeable on this forum that know much more than I do.

I'am so glad that @DigitalDaz set this forum up.

 

[John]

I'm sorry, I'm not sure what you mean by "subscribe to help posts". I just click on the "Whats new" tab, and any post that hasn't been answered, I try to provide some help. I normally leave unanswered posts a day before responding unless I absolutely know what the answer is. There are a lot of very knowledgeable on this forum that know much more than I do.

I'am so glad that @DigitalDaz set this forum up.

It is not the first time you are helping me. So thank you very much for that.

I was asking if there is a way that I could receive an email when someone asks for help, so I could also help if I knew the answer.

I guess there isn't. But at least I know how to look for it now.

 

[DigitalDaz]

Is this PBX on a LAN, I would guess so?

 

[John]

Is this PBX on a LAN, I would guess so?

Hi @DigitalDaz,

The VPSs on my dedicated server are all physically on one ethernet card. However, VPSs see themselves as they were connected to their own physical network. The network sees each VPS has its own MAC. Also, each VPS has its own dedicated public IP address. Default bridge mode.

Sincerely,

J