How does Cisco SRST help ensure the availability of telephone service on a converged network?

A.
When installed with Cisco CallManager on a server at headquarters, SRST automatically reroutes voice traffic to and from the branch offices to the PSTN if the WAN becomes congested.

B.
When installed on a router at a branch location, SRST automatically configures the local router to provide call processing for the IP phones if Cisco CallManager is unavailable because of a network failure.

C.
SRST allows legacy analog equipment at a remote site to connect to the packet-switched IP network if the IP telephones lose power.

D.
SRST, a QoS tool loaded automatically on Cisco routers used in a voice network, includes a management GUI that shows administrators the state of the network at all times.