Exam MS-720 topic 3 question 4 discussion

Actual exam question from Microsoft's MS-720

Question #: 4
Topic #: 3

You have a Microsoft Teams Phone deployment.
You have a PBX that connects to the PSTN by using an E1/T1 Primary Rate interface (PRI).
You plan to migrate to Direct Routing by using the existing PSTN services.
What should you install upstream of the PBX?

A. a physical Session Border Controller (SBC)
B. an FXO SIP Analog Telephony Adapter (ATA)
C. a virtual Session Border Controller (SBC)
D. a Session Border Controller (SBC) in Azure

Show Suggested Answer

Suggested Answer: A 🗳️

by jason6311 at Jan. 7, 2022, 1:08 p.m.

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jason6311

Highly Voted 3 years, 5 months ago

All other things being equal, a virtual SBC (whether hosted in Azure or not) or physical SBC is required for Direct Routing. But as far as I know, the only SBC's that are available with PRI interfaces (as opposed to SIP trunking) are physical. An ATA FXO SIP interface may or may not be required, depending on the specific SBC, but an SBC is certainly required. Therefore A is indeed the best answer IMO.

upvoted 6 times

DEberhardt

3 years, 3 months ago

indeed - the only reason you may want to use a physical SBC here is proximity to the PBX and performance due to the expected throughput. - We don't know enough about this scenario to advise whether the PBX can be replaced at all, where a combined GW/SBC would provide connectivity for E1/T1 trunk for.

upvoted 2 times

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[Removed]

Most Recent 2 years, 4 months ago

Selected Answer: A

Physical is correct

upvoted 2 times

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Khana

3 years, 5 months ago

a physical SBC is mandatory for connecting physical PRI lines for Direct routing

upvoted 1 times

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fejoes

3 years, 5 months ago

Local PBX might have the ISDN connectivity hosted, in this case no need to be a physical SBC, so a virtual SBC = Azure SBC can be SIP trunked in between Teams Tenant and PBX. Let us assume Physical one is the best answer here

upvoted 1 times

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