A. NCP
B. HDLC
C. LAPB
D. LAPD
Answer: D
Explanation:
The D channel remains up all the time so that new signaling messages can be sent and
received. Because the signals are sent outside the channel used for data, this is calles
out-of-band signaling. LAPD protocol manages D channel.
Reference: Cisco CCNA ICND 640-811 p.330
B. HDLC
C. LAPB
D. LAPD
Answer: D
Explanation:
The D channel remains up all the time so that new signaling messages can be sent and
received. Because the signals are sent outside the channel used for data, this is calles
out-of-band signaling. LAPD protocol manages D channel.
Reference: Cisco CCNA ICND 640-811 p.330