Laurens and Tilghman GeneralCom is implementing a Cisco IP Videoconferencing solution that includes a Cisco CallManager and a Cisco IOS Gatekeeper. The customer uses H.323 and H.320 devices exclusively. Video calls will use RTP streams for audio, video, and far-end camera control and a sequence of call control signaling messages. The customer is using the Alt-GK feature to protect the video telephony service from component failures. The customer is concerned that some of the existing H.323 devices may not support Alt-GK. What is the most cost-effective solution that will provide the resilience that the customer desires without upgrading or replacing the existing H.323 devices?

A.
Use Hot Standby Router Protocol.

B.
Use the gateway as a backup gatekeeper.

C.
All H.323 devices support Alt-GK.

D.
Cisco CallManager provides the backup gatekeeper function in conjunction with the existing video gateway.