T1 PRI call delay

[rmayer]

I noticed that my 3cx setup with the patton 4960 connected to a T1 PRI has almost a 1 second delay during conversations. We have another T1 PRI connected to our regular PBX which has almost no delay at all. What is interesting is if I call a DID on my regular PBX from 3cx there is no delay in that call (calling from one T1 to another), only when 3cx is dialing to the outside world is there a delay. I've tried swapping the T1 lines, but had the same issue. Is there anything that can be done?

 

[leejor]

A delay of that much would have to be caused by either distance or something buffering the data. If there is no delay on a call between the two PBX's, ie. out one PRI and back in on a second (through the same provider?), then I would have to make a guess that it is being introduced at the central office. The only real way to confirm that is to use monitoring equipment and listen on a channel on the PRI and see if the delay is the same as what you hear in the handset. You didn't say which way (both?) the delay was occurring.

 

[N_G]

There is definitely a configuration issue here. Could be some setting that needs to be done in the Patton depending on your T1. If you have a 3Cx support package, contact our support department and they will be able to help you. A one second delay is not normal.

 

[rmayer]

Both T1's are on the same provider. I don't think there is any problem with either T1 because there is no delay when I connect our regular PBX to either T1. The delay happens both ways. I am currently testing out 3cx as a replacement PBX so I do not have a support package. Any suggestions on configuration for the patton?

 

[Kevin Attard Compagno]

Hi there

What phones are you using to place the call? Do you get any different behaviour if you change phone model? Try using 3CX Phone, or X-Lite, for example...

Trying to see if it has to do with the way the phone builds the audio traffic packets...

Regards

 

[rmayer]

Tested with SPA504g, SPA942, 3cxphone, x-lite and a few other SIP softphones, all have the same issue.

I'm curious, what is an acceptable delay for the 3cx/patton system? Should it be the same as our regular hardware pbx (we currently have an NEC NEAX 2000 IPS), or will there be more delay by design? Timing the delay as best as I can it seems to be around 0.7 - 0.8 seconds, our regular pbx is no more than 0.1 - 0.2 seconds.

Thanks for your help!

 

[Kevin Attard Compagno]

Hi there

If the PBX, the Patton, and the phones are all on the same LAN, then the PBX will actually not be involved in any of the Audio exchange. The PBX will instruct the phone and the patton to exchange audio between themselves directly. And a wireshark capture running on the 3CX machine should confirm this - you should see NO RTP traffic coming from and to the PBX server.

Could you confirm this?

If you ARE seeing RTP traffic on the PBX machine when all 3 entities (pbx, phone, patton), then either the extension or the patton is set to "PBX delivers audio" - you should retry your tests with this option disabled for all components.

Regards

Kevin

 

[rmayer]

Confirmed, no RTP traffic is coming to and from the 3CX server when placing a call. Again, when I make calls from 3CX to my regular PBX there is no delay (they each have there own T1 line), only calls from 3CX to any other external source have a delay. I agree with the earlier statement that there is probably a configuration problem with the patton and our T1's.