Device Mobility + 911 Caller ID + Centralized SIP

[ashrafkhanm]

Hello Friends,

We have a centralized 11.5 CUCM cluster with multiple remote offices in US. We currently use Calling Party Transformation Mask for every site to display the corresponding site's main number for all outbound PSTN calls. We have centralized SIP circuits that transports all the PSTN traffic from all remote offices.

We would like to implement device mobility but trying to figure out the below two items.

1. When a phone roams and makes outbound PSTN, the CLID should be the visiting site's main number. We are trying to present the correct CLID especially if the calls is made to 911 while roaming.

2. The OnNet calls should still display internal DNs as CLID.

Please suggest how this can be achieved. 

Thanks in advance.

[Jonathan Schulenberg · Accepted solution]

If you’re using a classic Line+Device CSS design with the 911 Route Pattern on the Device-level CSS then this should work just fine with Device Mobility. Configure the roaming site-specific Device CSS on each Device Pool.

You actually have a second option in CUCM 11.5: the new Emergency Call Handler functions as a low-scale / low-resolution CER alternative. The ELIN is set at the time of the call based on the phone’s Device Pool at the time, including accounting for Device Mobility roaming.
https://www.cisco.com/c/en/us/support/docs/unified-communications/unified-communications-manager-callmanager/200452-Usage-of-Native-Emergency-Call-Routing-F.html

[ashrafkhanm]

Thanks Jonathan. That was really helpful. The native ELIN feature sounds interesting and it will suit our needs.

We currently have Calling Party Transformation Mask CSS applied on the SIP trunk for all outbound calls from multiple offices. This allow the callers to display correct CLID based on their phone extension. This gives us the flexibility of displaying the office's main number or the user's individual DDI.

Will the ELIN number and group settings override the Calling Party Transformation Mask applied on the SIP trunk if proper 911 route patterns are configured with the option "Is an Emergency Services Number" enabled??

I tried removing the Transformation Mask CSS from SIP trunk and applied on Device Pool/Phones. This resulted in displaying the full phone number as CLID for OnNet Calls as well. 

Thanks in advance.

Thanks,

Ashraf

[Jonathan Schulenberg · Accepted solution]

I haven't tried that combination, though the emergency call handler doesn't care whether the Route Pattern is truly an emergency number such as 911; you could test it with any off-net pattern (e.g. your cell phone, assuming it's not configured as a Remote Destination). The traditional answer was 'no': transformations occurring at the Route Pattern level would not override transformations farther downstream at the Route Group appearance on the Route List or at the Gateway/Trunk. The more common approach to outbound caller ID masking is to use the External Phone Number Mask field on the DN instead of a Transformation CSS on the Trunk/Gateway.

[Anthony Holloway]

Is this limited ER functionality in CUCM worth researching and deploying? I have not yet dug into the details, because I'm afraid I'll be disappointed. Thankfully, I still get to deploy CER these days.

[Jonathan Schulenberg]

Yes, I think it's a great feature for low-scale (100 ELIN max) / low-resolution (Device Pool, typically per-site) use cases. Layer 3 roaming on WLCs could hang you up here if you had a campus but the OP's environment sounds like a solid fit: branch offices with centralized trunking but [apparently] no serious E911 (e.g. floor/suite/sqft) requirements. It's pretty simple: turn it on, define the ELINs in whatever format you need, assign each Device Pool and ELIN Group, and flag the appropriate Route Patterns.

[Anthony Holloway]

Sounds easy enough. Thank you for the info!