Which statement about WAN protocols is correct?
- ATM differs from other WAN protocols in that it uses variably sized packets.
- Most WAN protocols use HDLC or a variant of HDLC as a framing mechanism.
- The frame header consists of the frame check sequence and cyclic redundancy check.
- ISDN differs from Frame Relay, HDLC, and ATM in that it is packet-switched rather than circuit-switched technology.
Exam with this question: CCNA Exploration 4: EWAN Chapter 1 Exam