CUCM 8.6 Integration to Nortel CS2100 SE16

[Andrew West]

Hey All,

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.

[brmeade]

What does the full SIP message exchange look like?

[Andrew West]

Here is a SIP call trace of a failed call from TranslatorX..

[brmeade]

Andrew,

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.

Brian

[Andrew West]

Hi Brian,

I just sent you a PM .

Thanks!

[brmeade]

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.

[Andrew West]

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.