Which of the following statements regarding Call Preservation is valid? (Choose all that apply)

A.
Call preservation is based on call signaling and call connections.

B.
If communications between devices is unaffected, the RTP streaming sessions cannot be preserved.

C.
Cisco CallManagers in a cluster use Physical Layer links to establish calls between devices registered to different CallManager servers.

D.
Cisco CallManagers in a cluster use Signal Distribution Layer links to establish calls between devices registered to different CallManager servers.

E.
The affected calls cannot be controlled by the CallManager cluster, if an error occurs that affects the signaling path, which is controlled by a CallManager server.

F.
The RTP streaming sessions can still be preserved, provided communication between devices are unaffected.