no ringback tone dialling external numbers

[andymars]

when placing a call from a grandstream gxp 2000 handset to an external number the line doesn't appear to ring:

there is a dial tone when the handset is picked up,
a number is dialled,
silence until the external number answers the call (no ringback tone)

this is probably handset specific since the softphone appears to work ok, can anyone suggest why there's no ringing?
(I've tried PBX delivers audio for the extension but this has no effect).

 

[leejor]

Re: no ringing when dialling external numbers

External calls to ...a gateway or VoIP provider? If a gateway, what make, what provider? Do you hear ringback tone when calling another extension? The softphone will usually give ringback tone "anyway" (double British style ringback tone), there is an option to suppress early audio so that you hear only the real ringback. So that may not be an indication that the Grandstream is to blame, just yet.

 

[andymars]

Re: no ringing when dialling external numbers

sorry via a voip provider (VoipOn), no PSTN Gateways/Lines in our system. There is a ringback tone to internal extensions, both from the softphone and grandstream (gxp2000) handsets.

 

[andymars]

Re: no ringing when dialling external numbers

bump, have checked the manual for the grandstream, unfortunately i don't have any other phones to test with - has anyone seen this before?

 

[leejor]

Once 3cx sends the dialled digits to the VoIP provider they should be sending back a message (SIP 183). when the call is answered the VoIP provider will send a SIP 200 OK message. If you use a program like Wireshark you can see these messages on the LAN ahead of 3CX. It sounds like the Grandstream isn't cutting through the voice-path until 3Cx receives the SIP 200 OK message.

 

[andymars]

right so would need something like a hub to capture the packets between voip provider and pbx, or can this be done on the server itself?

 

[leejor]

A second computer to run Wireshark and a hub (not a switch) to put between the modem and router, would work best (I've found). You may be able to run it on the same computer as 3CX, haven't tried that myself, but i can't see that it would hurt to try.

What VoIP provider are you using? Perhaps others have had problems with them as well. Some don't seem to adhere to SIP standards. It's a shame you don't have another VoIP hard phone or ATA to try.

 

[andymars]

tell me about it, don't have a hub either (very hard to come by these days). voipon is the provider, it would be odd if they weren't compliant since they're 'value-added distributors', i will try to get a wireshark trace from the server to check the SIP messages.

 

[andymars]

ok tried using a linksys/sipura SPA921 and get the same result, wireshark shows both the 100 trying and 183 signals:

 <int pbx ip>            217.14.132.172        SIP      Request: REGISTER sip:sip.voipon.co.uk:5060
  217.14.132.172        <int pbx ip>            SIP      Status: 200 OK    (1 bindings)
  80.169.52.233         <int pbx ip>            SIP      Request: REGISTER sip:<int pbx ip>
  <int pbx ip>            80.169.52.233         SIP      Status: 407 Proxy Authentication Required    (0 bindings)
  80.169.52.233         <int pbx ip>            SIP      Request: REGISTER sip:<int pbx ip>
  <int pbx ip>            80.169.52.233         SIP      Status: 407 Proxy Authentication Required    (0 bindings)
  <int pbx ip>            217.14.132.172        SIP/SDP  Request: INVITE sip:<ext number>@sip.voipon.co.uk:5060, with session description
  217.14.132.172        <int pbx ip>            SIP      Status: 100 Trying
  217.14.132.172        <int pbx ip>            SIP      Status: 407 Proxy Authentication Required
  <int pbx ip>            217.14.132.172        SIP      Request: ACK sip:<ext number>@sip.voipon.co.uk:5060
  <int pbx ip>            217.14.132.172        SIP/SDP  Request: INVITE sip:<ext number>@sip.voipon.co.uk:5060, with session description
  217.14.132.172        <int pbx ip>            SIP      Status: 100 Trying
  80.169.52.233         <int pbx ip>            SIP      Request: REGISTER sip:<int pbx ip>
  <int pbx ip>            80.169.52.233         SIP      Status: 407 Proxy Authentication Required    (0 bindings)
  80.169.52.233         <int pbx ip>            SIP      Request: REGISTER sip:<int pbx ip>
  <int pbx ip>            80.169.52.233         SIP      Status: 407 Proxy Authentication Required    (0 bindings)
  217.14.132.172        <int pbx ip>            SIP/SDP  Status: 183 Session Progress, with session description
  80.169.52.233         <int pbx ip>            SIP      Request: REGISTER sip:<int pbx ip>
  <int pbx ip>            80.169.52.233         SIP      Status: 407 Proxy Authentication Required    (0 bindings)
  <int pbx ip>            217.14.132.172        SIP      Request: REGISTER sip:sip.voipon.co.uk:5060
  217.14.132.172        <int pbx ip>            SIP      Status: 200 OK    (1 bindings)
  217.14.132.172        <int pbx ip>            SIP/SDP  Status: 200 OK, with session description
  <int pbx ip>            217.14.132.172        SIP      Request: ACK sip:1IzDRZXD0wT_-zPI5owBMncT0eFYLbj2MSpV_rUWN0DpzbYUQZcklk.@217.14.132.172:5065
  217.14.132.172        <int pbx ip>            SIP      Request: BYE sip:<voip id>@<ext pbx ip>:5060
  <int pbx ip>            217.14.132.172        SIP      Status: 200 OK

any suggestions?

 

[leejor]

Given that a second type of set is doing the same thing AND Wireshark shows the 183 message as expected, I began wondering about your router/firewall. I assume you are using one, or is the 3CX PC exposed to the net? If you are behind a router then try bypassing the router and putting the PC on a public IP. I came across this http://www.dslreports.com/forum/r20153741-No-ringback-behind-cisco-NAT-router showing a similar problem caused by a router. Wondering if you might be experiencing the same thing. Taking the PC from behind the router, just for a short test, would show if it is in fact causing the problems.

 

[andymars]

it is behind a firewall with the ports exposed (3cx is on 2008 VM) - it's actually a SmoothWall which got me thinking about their SIP Proxy features on the firewall. it should be disabled leaving SIP traffic untouched, but will look into it - thanks for the suggestion

 

[semn]

Re: no ringing when dialling external numbers

External calls to ...a gateway or VoIP provider? If a gateway, what make, what provider? Do you hear ringback tone when calling another extension? The softphone will usually give ringback tone "anyway" (double British style ringback tone), there is an option to suppress early audio so that you hear only the real ringback. So that may not be an indication that the Grandstream is to blame, just yet.

Can you tell me how should i supress the early audio sound? I install in my office a 3cx server and i receive complains from my colleagues. Actually this is only one complains received. So if you can, please tell me how should i configure the 3cx box to receive the real ringback sound.

Thanks
George

 

[andymars]

this is exactly my problem, the phones receive the 'early-audio' so dont generate the ringback but 3cx isnt doing it either - so there's nothing heard until the person being called picks up. if i work it out i'll post a solution

 

[leejor]

Can you tell me how should i suppress the early audio sound?

As I recall, that was only an option in the 3CX softphone. Sorry, I don't have a PC in front of me with it on and I don't use it very often.

An audio path should be cut through from the VoIP provider when 3Cx receives the SIP 183 session progress message and at that point you should receive ringback/busy etc.. The 183 message also contains info about the RTP port assigned to the call, that is why I was wondering if your router/firewall is somehow manipulating the SIP messaging. Were you able to try running 3CX "exposed" to the net as a test?

 

[andymars]

i think it would be difficult to do using a VM - i could be wrong, also I don't really have the hardware in place to try it 'in front' of the firewall

 

[leejor]

Then I don't know what else you can do to troubleshoot to determine if it is a firewall/provider/3CX issue without eliminating the firewall temporarily.

 

[andymars]

ok so i got round to trying this, moved 3cx to a different site behind a different firewall (DrayTek Vigor 2910) restarted all the services, reconfigured/restarted the tunnel (to point to the new external IP) and finally reconfigured the phone (to point to the new PBX IP address).

the behaviour is the same...no ringback tone on external numbers

 

[pjr]

was this issue ever resolved?

we have exactly the same problem with Polycom phones connected via VPN to a hosted 3CX server.

we can even see/hear the ring back tone on a wireshark capture of a call when the person making the call doesnt hear it?!

 

[andymars]

i think that might be different. it seems in my case (looking at the wireshark captures) that the SIP Proxy Tunnel isnt forwarding the RTP packets to the phone until the call is connected.
if you're using a direct VPN link but you can see the RTP packets coming back, then it sounds like your phone isnt generating the ringback when it should. can you try another handset? most phones should check for early-media and if they dont get it generate the ringback tone themselves. if they do get the early-media (like when i use the 3cx tunnel) then the pbx should generate the ringback tone.

this is my understanding anyway, if I am wrong someone plese correct me...
i've logged this with 3cx anyway and will let you know if this is a bug or a configuration problem.

 

[StaffKB]

Hi,

In the exact same scenario does this occur if you use 3CX Voip Phone?

What is the firmware of the grandstream?