单项选择题

Which one of the WAN data-link protocols below is used for out-of-band signaling?（）

A. HDLC
B. NCP
C. PAP
D. LAPD
E. LAPB
F. None of the above

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多项选择题

Which of the following correctly describe characteristics of PPP?（）

A. Encapsulates several different types of routing protocols.
B. Supports only IP.
C. Can be used over analog circuits.
D. Is proprietary to Cisco
E. Supports error correction.

多项选择题

What are some common layer 2 encapsulations for a WAN link?（）

A. Ethernet
B. PPP
C. Token Ring
D. HDLC
E. Frame Relay
F. POTS