CUC to CUCM SIP Integration Trunk Settings

[j.a.m.e.s]

I'm preparing to migrate our CUC from SCCP -> SIP, but I'm struggling to work out how CUC uses the following settings (most are on the SIP Trunk).

• Inbound Calls CSS
• Rerouting CSS
• Out-of-Dialog Refer CSS
• Diversion Header Enabled inbound and outbound
• Calling Party Selection: Originator / Last Redirect Number
• CSS also needed on the Voicemail Pilot

Would anyone mind commenting on the above please? For example, which CSS will be used to dial the MWI numbers? Which will be used for supervised/release to switch calls? How is the diversion header used by Unity? When does CUC do an out-of-dialog REFER?  Why does the CSS on the Voicemail pilot need access to the CUC route-pattern as well as access to the phone DNs?

There is mention of configuring the above in the CUC SIP Integration Guide, but there's not enough commentary of the underlying operation to know what should be done.

[j.a.m.e.s]

Having read a few more posts I'm piecing this together slowly. Sorry if this raises a few more questions, but to summarise my understanding so far:

• Inbound CSS: Used when CUC does a "Supervised" call transfer
• Rerouting CSS: Used when CUC does a "Release to Switch" call transfer
• Out-of-Dialog Refer CSS: This is used for unsolicited NOTIFY messages sent by CUC. MWI extensions are not used in a SIP integration, hence this CSS needs visibility of all DNs which may need a voicemail notification.
• Diversion Header: This is set on INVITE messages send from CUCM -> CUC. This header is used by Unity to select the mailbox (I think). I'm not completely sure but I think this header could be influenced by 1) VM Profile Mask, 2) "Calling Party Selection" on the trunk and 3) Redirecting Party Transformation CSS. I'm also wondering if a rogue diversion header could arrive via CUBE/PSTN and if this would impact CUC or would just get overwritten.
• Voicemail Pilot CSS: This number used when 1) a person presses the Voicemail key or 2) a call hits a DN where the Voice Mail box is checked. The CSS therefore just needs visibility of the RP leading to the CUC Trunk (I think). I don't know why Cisco suggest giving visibility of all user DNs as well

[Maren Mahoney · Accepted solution]

Inbound Calls CSS - When CUC outdials on behalf of users. An example would be for Message Notification (so this CSS should include PSTN patterns).

Re-routing CSS: If a call flows into CUC by redirect, and then back out again to CUCM because of CUC programming, this CSS determines the targets. Let's say a CTI Route Point takes some kind of pilot number and sends the call directly to CUC to hit a System Call Handler, then the caller presses "7" to be transferred to a number. Or, you have all calls flow through CUC as a company auto attendant and the caller "dials an extension at any time".

Diversion Header Enabled inbound and outbound - SUPER important. This is the feature that carries the forwarding information for a call to CUC. For instance, I call you and your phone rings and you don't answer and the call rolls to voicemail. CUCM (SIP "From") signals to CUC (SIP "to") that there is an inbound call, but CUCM has to carry the original calling and called party (Diversion information carried in the Diversion Header) so that CUC can process the call.

Calling Party Selection: Originator / Last Redirect Number - For calls that are redirected more than once, which redirect information should CUC pay attention to. For instance, you forward your number to Pat. I call you, the call is redirected to Pat but Pat doesn't answer and Pat's number rolls to voicemail. Should CUC pay attention to the first redirect number (yours) or the last redirect number (Pat's). There are call routing implications for both of these. Note, also, that Call Routing Rules can pay attention to Redirect information as well.

I hope this helps!

Maren

[j.a.m.e.s]

Thanks a lot Maren, this is useful info. For the 'Calling Party Selection' does this have some impact on the diversion header itself? I would like to understand at the SIP level what this does if possible.

Note: I can see this can be set on the CM trunk or on CUC under Advanced-> Conversations

[Maren Mahoney]

The Calling Party Selection is used to tell CUC how to evaluate Diversion information if there has been more than one diversion. Should CUC use the first diversion header information (I called you, and you forwarded your phone to Pat. So the first Diversion Header would include that I am the calling party and you are the called party); or should CUC use the second diversion header information (Pat's number rolled to voicemail. So the second Diversion Header would have me as the calling party but Pat as the called party, unless some mechanism also changed the calling party at Pat's device such as a transform).

Both Diversion Headers would be present in the SIP INVITE that CUCM sends to CUC. And there are certainly situations where there could be third or even fourth Diversion in a call. Which one should CUC pay attention to when determining what to do with the inbound call? The choices are only the first or the last (and not any interim). 

Does that help?

Maren