Difficulty: Easy
Correct Answer: A very common bit-oriented data link protocol issued by ISO.
Explanation:
Introduction / Context: HDLC is a foundational, bit-oriented data link protocol used for point-to-point and multipoint links, influencing protocols such as PPP and LAPB.
Given Data / Assumptions:
Concept / Approach: HDLC defines framing, error detection, and control mechanisms (I/S/U frames). Being bit-oriented means control is defined at the bit level (flags, bit stuffing) rather than fixed byte boundaries for characters.
Step-by-Step Solution:
1) Frames are delimited by flag 01111110.2) Bit-stuffing prevents accidental flag patterns in payload.3) CRC provides error detection.4) Control field supports reliable data transfer and link management.Verification / Alternative check: Compare with PPP, which borrows HDLC framing style for serial links.
Why Other Options Are Wrong:
Medium access control schemes (options A and B) describe contention/token systems, not HDLC's role.Circuit-switched access standards (option D) describe network access, not a data link framing protocol.“None of the above” is wrong since option C is correct.Common Pitfalls: Confusing HDLC with MAC methods like CSMA/CD or token passing; assuming byte-oriented protocols like PPP are unrelated.
Final Answer: A very common bit-oriented data link protocol issued by ISO.
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