You support a WLAN using dual-band 802.11ac three stream access points. All access points have both the 2.4 GHz and 5 GHz radios enabled and use 40 MHz channels in 5 GHz and 20 MHz channels in 2.4 GHz. A manager is concerned about the fact that each access point is connected using a 1 Gbps Ethernet link. He is concerned that the Ethernet link will not be able to handle the load from the wireless radios. What do you tell him?
Due to 802.11 network operations and the dynamic rates used by devices on the network, the two radios will likely not exceed the 1 Gbps Ethernet link. The access points operating with 3 spatial streams on both 2.4 GHz and 5 GHz bands are unlikely to produce a total data rate that exceeds the 1 Gbps Ethernet link, especially considering that the 802.11ac standard involves dynamic rates and other network operations that prevent constant maximum data throughput.
Each AP uses 3 spatial streams, is 802.11ac-compatible and will operate at both 2.4GHz and 5GHz (since it is dual-band and has both 2.4GHz and 5GHz radios enabled). For 5GHz communications, it will operate optimally according to the 802.11ac standard: - Max data rate here is 6933.3Mbps, for max channel width of 160MHz and max of spatial streams of 8. - Since it is operating with a configured channel width of 40MHz (ie 1/4 of max channel width), and 3 streams (ie 3/8 of max spatial streams), its operating data rate is: 6933.3*(1/4)*(3/8) = 650Mbps For 2.4GHz communications, it will operate optimally according to the 802.11n standard (since 802.11ac does not support 2.4GHz): - Max data rate is 600Mbps, for max channel width of 40MHz and max spatial stream of 4. - Since it is operating with a channel width of 20MHz (ie 1/2 of max channel width) and 3 streams ( ie 3/4 of max spatial stream), its operating data rate is: 600*(1/2)*(3/4) = 225Mbps. Thus total data rate for communications on both bands = 875Mbps. We can then say that the 1Gbps is adequate. Hence D is correct.
D is correct
Upgrading to 10Gbps is not the correct solution. They are using 802.11ac APs which in all probability do not support 10Gbps uplinks. 802.11ax APs are the first of their kind that support mGig ethernet. 802.11ac does not.