Which high-availability mechanism is specifically designed to protect branch sites from WAN failures?

• A. DNS SRV
• B. CUBE
• C. Informix SQL
• D. SRST

Answer: (D)

Survivable Remote Site Telephony is designed to keep branch-office telephony working when the WAN link to the central call-control cluster is down. It does this by enabling the local router to take over call processing for registered IP phones at the branch, allowing internal calls to proceed and providing access to the PSTN gateway for outbound calls. This keeps essential voice communication available even during WAN outages, which is exactly what a branch-site high-availability mechanism should do.

DNS SRV is about locating services for clients, not maintaining call processing during network failures. CUBE acts as a border element for voice and media with service-provider or remote sites, but it’s not a dedicated branch survivability mechanism. Informix SQL is a database and unrelated to voice high availability.