MS Teams roaming

[saroshjabran]

Hi

How does MS teams server know which country user is currently in when receiving a call on a landline number. For example, the user has UK landline number on teams account and if the user receives a call (while abroad), the caller get a ringing tone that is from abroad instead of normal UK ringtone.

I suspect when the user register while abroad the servers recognise the IP of user which is not from UK or the the fact the the user registers to a non-UK Teams server because of DNS but I want to know precisely how it works please.

Thanks

[#2]

@Linus Cansby

[#3]

Admins can setup Emergency locations so that correct location information is sent to your PSAP, this can use IP subnets and switch ports to see the location of the user. But this is not used for call routing of regular calls.
Plan and manage emergency calling - Microsoft Teams | Microsoft Docs

Location Based Routing is also checking the location of the Teams client, but that is used to make sure that the user dials out from the site that they are located. So if you have setup Direct Routing with Location Based Routing that could be why you hear different ringtones.

Plan Location-Based Routing for Direct Routing - Microsoft Teams | Microsoft Docs

If LBR is not implemented the Voice Routes you have setup decides where to send the call and that is based on the number you dial.

[#4]

@Linus Cansby 

Thanks for reply. So if I understand correctly, the call is routed based on the location of the user and how the admin has configured the service. But my question is around how the Teams client/server determine the location of the user to begin with ? The public IP of the user OR which Teams server the login request is forwarded to (because of DNS) and something else ?

Thanks

[#5]

Teams client will connect to different URLs using DNS to connect to the closest data center, ex. using  teams.microsoft.com. But it will always connect to your home tenant, the data center were your data is stored. 

For media (audio/video) Teams will use Anycast IP (13.107.8.2) to connect to the closest media relay. But the media when you dial a PSTN phone number will always go out via the SBC that your admin setup.