Which WAN protocol is used for out-of-band signaling?（）

A. To ma a known IP address to a MAC address
B. To map a known DLCI to a MAC address
C. To ma a known MAC address to an IP address
D. To ma a known DLCI address to a IP address
E. To ma a known IP address to a SPID address
F. To ma a known SPID address to a MAC address

A. T1
B. Frame Relay
C. DSL
D. PPP
E. ISDN
F. IPX