We got a call from a customer who said that calls were being dropped when someone paged. We worked with the customer to reproduce the issue and here is what is happening: One person is making an outbound call and hearing ringback as they wait for the call to be answered. During that time, someone else makes a page. After the page, the person making the outbound call hears silence and thinks that their call has been disconnected. In actuality, the're just not hearing the ringback. The call will complete as normal if allowed to do so.

The system in question is a 7400, but I have also reproduced this issue with a 7100. The extensions are all IP. The issue affects the extensions in the page group receiving the page. Other stations are unaffected.

I look forward to hearing your thoughts on this.

How many IP stations are on your paging group? How many MGI channels do you have in place? Are they SIP or Analog trunks?

The customer system has about 50 station in the "all page" group. There are three OAS cards in the system for a total of 48 MGI channels and they are using SIP trunks.

I also see the same behavior on my little 7100 test system here at the office which has 15 IP extensions (all in one page group) and only 4 MGI channels. It also uses SIP trunks.

I'm hoping to be able to do some additional testing on a system with analog trunks.

The problem is that the paging is taking up your MGI channels. Do you have the MPS/RTG ports forwarded? This may minimize the use of IP to SIP MGI and use the MPS ports instead. Paging to IP devices always uses MGI.

I have run into that problem in the past, but not with multicast paging. The system is using multicast paging, so MGI channel usage for paging is not an issue. Also, we are using MPS on this system so MGI usage is further minimized.

Samsung support suggested that we enable "Real Ringback" under DM 5.2.18. Tested in the office on Friday and appears to resolve the issue. I will follow up with the customer today to make sure that it also resolved the issue on their system.