Security mode throughput
The 854T supports WEP 64/128 and only "Personal" (PSK) mode for WPA and WPA2. Figure 13 shows uplink throughput for unencrypted, WEP 128, WPA-PSK/TKIP and WPA2-PSK/AES modes taken in 300 Mbps mode.
Figure 13: Security mode throughput comparison - uplink
I had no problem connecting in any of these modes, and was pleased to see only a 15% throughput penalty using WPA2/AES, which provides the best secured performance. This is half the 30% throughput hit of the D-Link DIR-655 / DWA-652 combo using the same mode.
The throughput hit for WEP 128 is actually slightly less than for WPA/TKIP, but both are around 35%. But more importantly, unlike the D-Link DIR-655, the 854T doesn't switch to legacy 802.11b/g mode when WEP is used.
Figure 14 compares downlink throughput for the various security modes. You can see higher throughput variation, in all but WPA/TKIP, which comes in dead last with a 45% throughput reduction. By comparison, WEP 128 only suffers a 30% throughput loss.