With the release of Exchange 2010 SP1 we have seen some issues integrating with Nortel CS 1000. Nortel CS 1000 is currently not part of the Telephony Advisory Program and not certified for Exchange 2010 & 2010 SP1. It is currently supported only when it connects to Exchange UM through one of the supported IP gateways - Dialogic DMG, Audiocodes, etc.
To connect a call to UM the gateway first connects to it the UMService running on port 5060\5061 and then the call is immediately transferred to the UMWorkerProcess on port 5065\5067. You can know more about the process here. This transfer is basically a redirect done by SIP message 302 Moved Temporarily containing a Contact header that tells the gateway where to connect to the UMWorkerProcess.
You may experience an issue where once a user connected to Nortel CS1000 calls into Exchange UM he hears dead air. The call is never connected to any of the UM features - voicemail\ subscriber access\ auto attendant. We have seen this issue with version 5.x and 6.x.
After investigation we have found that at times Nortel CS 1000 is not able to understand this Contact header needed to route the request to UMWorkerProcess. This occurs when the Contact header contains an optional maddr parameter (multicast address) containing the domain that needs to be communicated to continue this call.
Now, this maddr parameter is added to the Contact header by UM only if the incoming INVITE into UM contains the optional maddr parameter in the Request line -
Request-Line: INVITE sip:3213;email@example.com;maddr=10.10.10.1;transport=tcp SIP/2.0
If you view this in Network Monitor\ Wireshark you will see that the second INVITE into the UM worker process is never received at the UM server -
Instead of -
The result will be dead air/unable to connect the call.
Audio Codes, Dialogic among other supported gateways give the ability to either strip the optional maddr parameter or can route the traffic for that domain to a particular gateway. They have also been certified to work with Exchange UM 2010\2010 SP1. It is advised that a supported gateway be introduced to connect with Exchange UM 2010 SP1 till we are able to certify Nortel CS 1000.