Wireless Performance – Secure modes
The good news is that the N1 supports a full range of wireless security options, including WEP 64/128, WPA PSK and “Enterprise” and WPA2 PSK and “Enterprise”. The bad is that, in most cases, you will pay a severe penalty for trying to secure your wireless LAN.
Figure 18 shows simultaneous up and downlink performance when WEP128 encryption is enabled. While it’s nice to see the dropout problem solved, total average throughput drops by about 63%! Also note that downstream data takes a worse throughput hit than upstream. But wait, there’s more!
Figure 18: Location 1 throughput – WEP 128 simultaneous up and downlink (click to enlarge)
Figure 19 shows what happens when WPA-PSK TKIP security is used. I ran the test multiple times, but the 87% drop in throughput looks like it’s real and repeatable.
Figure 19: Location 1 throughput – WPA-PSK TKIP simultaneous up and downlink (click to enlarge)
Pressing on, I finally tried WPA2-PSK AES encryption, which presents the toughest computational load. Surprisingly, you can see that throughput suffers only around a 30% reduction, although with high variation.
Figure 20: Location 1 throughput – WPA2-PSK AES simultaneous up and downlink (click to enlarge)
When I shared these results with Belkin, they confirmed the behavior and offered this explanation:
…regarding your concern about low WEP and WPA-TKIP performance, basically we implemented our firmware per IEEE draft 1.0 spec, which only enables 11n aggregation in WPA-AES or OPEN modes. Therefore when WEP or WPA-TKIP is deployed no aggregation is used. The performance numbers that you are seeing are suggesting that behavior, which is the normal behavior.
I had thought my days of having to check secure-mode performance were over, but this experience has taught me that I’d better continue to keep an eye on this for the foreseeable future.