Which switching method uses the CRC value in a frame for its operation?

• A. Cut-through
• B. Fast-forward
• C. Fragment-free
• D. Store-and-forward

Answer: (D)

In Ethernet switching, the method that uses the CRC (Frame Check Sequence) as part of its operation is store-and-forward. It receives the entire frame, checks the CRC to verify frame integrity, and only then forwards the frame to the destination port if the CRC is valid. This approach ensures that only error-free frames are propagated through the switch, at the cost of higher latency proportional to the frame size.

By comparison, other methods forward frames based on header information without waiting for a full frame or validating the CRC before forwarding. Cut-through and its fast-forward variant send the frame as soon as the destination address is read, minimizing latency but not using CRC to make the forwarding decision. Fragment-free sits between these, waiting for enough data (often the first 64 bytes) to reduce the chance of forwarding some corrupted frames, but it still doesn’t rely on CRC verification to decide whether to forward.