What is the difference between half-duplex and full-duplex?
Why Interviewers Ask This
This question tests conceptual clarity. Interviewers want to hear a precise, confident definition before moving to more complex Networking topics. It also reveals how well you can explain technical ideas to non-experts.
Answer
Half-duplex communication allows data to flow in both directions but only one direction at a time — like a walkie-talkie. One party transmits while the other listens, then they switch. Ethernet hubs operate in half-duplex — only one device can transmit at a time on a segment, and collisions can occur (managed by CSMA/CD). Full-duplex allows simultaneous transmission in both directions — like a telephone. Modern Ethernet switches operate in full-duplex, eliminating collisions because each switch port has a dedicated path. Full-duplex effectively doubles the available bandwidth compared to half-duplex on the same link (e.g., a 100 Mbps full-duplex link can simultaneously send and receive 100 Mbps each). Modern networks almost universally use full-duplex since hubs have been replaced by switches. Duplex mismatch (one side full, other half) causes poor performance and high collision rates.
Common Mistake
Don't just define the term — demonstrate that you understand when to use it and when not to. Showing awareness of trade-offs is what separates average from strong Networking candidates.
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