Which two events describe the relationship of an IP phone to its secondary Cisco Unified CallManager system? (Choose two.)
A.
The IP Phone sends a TCP connect message.
B.
The IP Phone sends a TCP keepalive message every 30 seconds.
C.
The IP Phone sends a TCP keepalive message every 60 seconds.
D.
The IP Phone attempts to register with the secondary system when the primary system is unavailable.
E.
The IP Phone registers with the primary system when the secondary system is unavailable.
F.
The IP Phone registers with all the Cisco Unified CallManager systems in the group simultaneously, including the secondary system.