Duplex Mismatch in Ethernet Networks: Impact on Performance

Error Statistics Caused by Duplex Mismatch in Ethernet Networks

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Question

In Ethernet networks, duplex mismatches will lower performance. Which error statistics can be seen if a duplex mismatch is present?

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Explanations

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A. B. C. D.

C

On an Ethernet connection, a duplex mismatch is a condition where two connected devices operate in different duplex modes, that is, one operates in half duplex while the other one operates in full duplex.

This results in the full-duplex side receiving an incomplete frame with CRC error or a runt frame. It does not detect any collision since CSMA/CD is disabled on the full-duplex side. As a result, when both devices are attempting to transmit at (nearly) the same time, the packet sent by the full-duplex end will be discarded and lost due to an assumed collision and the packet sent by the half duplex device will be delayed or lost due to a CRC error in the frame.

A duplex mismatch occurs when two devices connected to each other operate at different duplex modes, either half-duplex or full-duplex. This situation often happens when one device is configured for full-duplex and the other for half-duplex.

In half-duplex mode, a device can either transmit or receive data at any given time, but not both simultaneously. Therefore, only one device can send data while the other device waits. In contrast, full-duplex mode allows devices to transmit and receive data simultaneously, improving network performance and reducing collisions.

When a duplex mismatch occurs, the device configured for full-duplex mode will continue to operate at full-duplex while the other device operates at half-duplex. As a result, the device operating in half-duplex mode will experience a higher number of collisions due to the fact that it is not capable of transmitting and receiving simultaneously. The device configured for full-duplex mode will not detect collisions since it can transmit and receive simultaneously.

Therefore, the correct answer is option C. In a duplex mismatch situation, collisions will occur on the half-duplex side due to the inability to transmit and receive simultaneously, while framing errors will occur on the full-duplex side due to the inconsistent traffic flow. Collisions on the full-duplex side and giants on the full-duplex side are not possible in this scenario, while runts on the half-duplex side are unlikely.