Microsoft Exchange Server 2013: Connectivity, Clients, and UM

What happens when the phone rings

Now would be a good time to examine what actually happens when Exchange is asked to answer a phone call. Assume that Alice wants to call Bob. This can happen in several ways. In order of increasing complexity:

• Alice and Bob have extensions on the same IP PBX.

• Alice and Bob are on different PBXs within the same UM dial plan.

• Alice and Bob are on different PBXs in different UM dial plans.

• Alice’s call is arriving from the PSTN.

Interestingly, we can substitute “an automated attendant” or “Outlook Voice Access” for Bob in the preceding list, and not much changes; the steps Exchange carries out after answering the call will be different, but the basics of call routing and answering remain the same.

Here’s what the basic ...