What are three requirements for the implementation?

You have a Microsoft Teams Phone deployment.

You need to implement PSTN connectivity by using Direct Routing.

What are three requirements for the implementation? Each correct answer presents part of the solution. NOTE: Each correct selection is worth one point.
A . a Session Border Controller (SBC) that uses a hostname in the onmicrosoft.com domain
B . a firewall rule that opens a TCP signaling port to Microsoft Teams
C . a public DNS entry that maps the FQDN of the Session Border Controller (SBC) to a public IP address
D . a firewall rule that opens a UDP signaling port to Microsoft Teams
E . a Teams-certified Session Border Controller (SBC)

Answer: B,C,E

Explanation:

Reference: https://docs.microsoft.com/en-us/microsoftteams/direct-routing-plan