Previously we had integration to a Nortel CS2100 working great via a SIP trunk.
Recently we had to upgrade the Nortel to SE16 and since then I have been having an issue with the following call flow.
1. Call originates from Cisco IP(SIP) phone to a Nortel TDM phone over the SIP trunk and if that TDM phone hunts to VM I get dead air for 11 seconds then the call drops. If the TDM phone is hard forwarded into VM then their is no issue, it is only when it hunts.
- I mentioned Cisco IP(SIP) above because it does not drop if it is from a SCCP phone like a 7925 WIFI phone or a soft client like IP communicator or even the SIP trunk I have for Microsoft Lync.
In looking at logs on RTMT I am now seeing re-invite inside a re-invite error(in red below) messages which you can see in the screenshot below (sorry for the blackout but infosec policy required it) . Anyone have any ideas? I do have a TAC case open but I am really trying to get this fixed before everyone comes back from the holiday.
So the issue here is CUCM and the Nortel system are both trying to Re-invite at the exact same time. If you have SDI/SDL traces, I could take a look at what is triggering the Re-invite on the CUCM side.
Just wanted to update everyone on here with the details I found in the traces. CUCM was doing Early Offer to the Nortel side and the 200OK from Nortel still had 2 codecs listed rather than one causing CUCM to immediately Re-Invite with G./711ulaw only. It looks like the Nortel system doesn't know how to handle inbound early offer. Solution will be to turn off Early Offer on the CUCM SIP Profile.
Brian has really been amazing with this issue.
Tomorrow I will create a new SIP profile and temp point my SIP trunk to that to see if it makes a difference once I do some testing I'll post the findings here.