Acme Company has offices around the country. With the use of Cisco Unified CallManager, the company has deployed a VoIP network in a multisite centralized configuration. Which IOS gateway feature should be deployed to enable VoIP devices to register with a local gateway and continue to function when the connection to the Cisco Unified CallManager is broken?
A.
Gatekeeper multizone
B.
Call Admission Control (CAC)
C.
Automatic Alternate Routing (AAR)
D.
Survivable Remote Site Telephony (SRST)