SIP Trunks and Answer Supervision on Mitel 3300 MCD

[ralph]

I have a setup where I have a specialized application server connected to the 3300 via SIP trunks.
Certain calls are routed inbound to the 3300 on the SIP trunks and then outbound to the PSTN via PRI trunks.

This issue I'm working on is that we appear to be receiving a "Fake Answer" when the calls come through the SIP trunk.
We get normal answer supervision when calling the same number via a 53xx phone.

My Q is: is there a way to control answer supervision on SIP trunks when they hit a PRI?

Ralph

[Tech Electronics]

Ralph,

I am just learning how the 3300 handles SIP, but have you looked at Force sending SDP in initial Invite - Early Answer under the SIP Peer Profile / SDP Options?

Thanks,

TE

[eugenej]

hmmm, I'm fairly familiar with SIP so I'll try help

what is the issue you are having? I understand the question around answer supervision but what is actually happening or not happening?

by nature SIP doesn't have answer supervision, however early media options as alluded to in the previous post and PRACK normally helps with PSTN related SIP issues

[ralph]

Hi eugenej,
The problem has to do with call twinning.
An incoming call rings to a device that is twinned to an external phone.
The SIP trunks tells the system that the call has been answered.
This calls the twinning to fail.

I understand that the engineers that were working on this issue in our lab has resolved the problem but they haven't told me what they did yet.  When I find out I'll post.

Ralph

[MrShides]

Ralph,

Did you solve this, I'm having the issue after a number port.  I've reached out to the vendor that is stating he thinks its the telco.

[MrShides]

WE SOLVED THIS!

It was on att side.

They have to select the following options:

Register with SIP server(Optional): CHECK
Send CONNECT after EARLY MEDIA: UNCHECK

This solved our issues.