802.11b Client Impact Mitigation Techniques

B.

The correct answer is B. Make 11 Mb/s the lowest mandatory rate.

Explanation:

In a mixed-mode environment where 802.11b and 802.11a/g/n/ac clients coexist, 802.11b clients can significantly impact the performance of the network due to their limited throughput and use of the 2.4 GHz frequency band, which is more prone to interference and congestion.

To mitigate the effects of 802.11b clients on the rest of the network, it is recommended to make 11 Mb/s the lowest mandatory rate. This is because 802.11b clients can only transmit at a maximum rate of 11 Mb/s, and if this rate is set as the lowest mandatory rate, the access point will not communicate with clients that cannot achieve this rate.

This forces 802.11b clients to either upgrade to a higher-capacity 802.11a/g/n/ac network or stay disconnected, thus reducing the overall contention on the wireless medium and improving the performance of other clients.

Option A, "Restrict OFDM modulation from being used," is not a recommended solution because OFDM modulation is used by higher-capacity 802.11a/g/n/ac clients, and disabling it would limit their performance.

Option C, "Enable a separate SSID for 802.11b clients," is also not a recommended solution because it would create a separate network for 802.11b clients, which could lead to management overhead and could also cause interference with the other networks.

Option D, "Enable a short preamble," is not a recommended solution because a short preamble is used by 802.11b clients to reduce overhead and increase throughput. However, it can also cause more collisions and retransmissions, which can further degrade the network performance.