Wireless Access

How much overhead does encryption add to the wireless traffic, and what sort of speed reduction would be considered "normal" for a network using WPA w/TKIP versus an Open (captive portal) network?

I seem to remember that our engineer also told us that using TKIP would also reduce our speeds (something about checking the "legacy" box) and that moving to WPA2 w/AES would give us better performance.

The problem I'm having is that our secure network users are starting to complain about the speed of the network versus the open network.  In some cases we are seeing a reduction of close to 50% (18Mbps on open vs. 9-10Mbps on WPA).  I've had a rare instance of a report of 5Mbps on WPA and 14Mbps on open.  Upload speeds don't seem to vary, only the download speeds.

We've been using this design for almost 2 years, so I'm not sure why people are just now starting to complain, but the complaints have gotten bad enough that  they are making their way to management.

Revamping the network to move to WPA2 w/AES is on my list of things to do........would I see any speed improvements?

Branch offices:  620 controller with AP93 (2.4ghz).

I'm open to any suggestions....not sure what to tell management at this point.

Not a big difference, but as more and more wireless-capable clients get on the network, the more degradation will be noticed...

Full 802.11n rates are only achievable when using either Open (no encryption) or AES encryption.  So based on this it is certainly possible that the use of TKIP is degrading speeds.  However, as Colin mentions there could be many other contributing factors (such as more wireless capable clients getting on the network).  If this is becoming a visible problem I would certainly contact TAC 800-WIFI-LAN to get further tuning reccomendations specific to your deployment.  More information on AES, TKIP and the performance impact can be found in the 802.11n VRD - http://www.arubanetworks.com/vrd/80211nNetworksVRD/wwhelp/wwhimpl/js/html/wwhelp.htm#href=Title.html 

Thanks for the link, that has some really good info.

When we set up the system I remember having to check the box for legacy clients, and our rep warned us it would reduce our speeds.  Suddenly almost 2 years later people are starting to complain.

I guess now is a good time to figure out how to transistion from WPA/TKIP to WPA2/AES.