Direct Routing questions

[David Phillips]

I've been looking over the documentation for Direct Routing and have a few questions.

• Is it possible to configure direct routing for users with phone numbers we obtained from Microsoft?
• We are in SfB hybrid right now, however won't be once we complete our migration to Teams.  The documentation only references configuring the OnPremLineURI parameter.  What is the significance of the OnPremLineURI if we eventually won't be in SfB hybrid mode?

[#2]

I guess maybe the answer to the first question is answered in the documentation on how many phone numbers we can get - it's based on the number of domestic calling plans we purchase.  So putting two and two together, we can't really just grab a bunch of numbers to use with direct routing.

https://docs.microsoft.com/en-us/MicrosoftTeams/getting-phone-numbers-for-your-users

[#3 · Accepted solution]

@David Phillips 

The purpose of Direct Routing is to allow you to enable calling in Teams using a third-party PSTN provider, using the phone numbers provided by that third party. In theory, you could obtain numbers from Microsoft and then immediately request them to be ported to the third-party PSTN provider, but why would you? It would be a lot easier to just obtain them directly from the provider.

If you are using Direct Routing, when a call comes in to your SBC and gets routed in to Teams, it arrives with a REQUEST header like sip:+18338006777@sip.pstnhub.microsoft.com, where the +18338006777 portion is the number the caller dialed. Teams routes the call to the user in your tenant with that number in their OnPremLineURI attribute.

[#4]

@Ryan Steele thanks for the info on OnPremLineURI, it makes sense now. 

100% agree on porting numbers, however right now it's taking months to complete number ports due to backlog, so I was hoping for a simpler solution.