Craig,
Do not use load balancing for latency-sensitive WLANs, especially voice WLANs. Rejecting voice clients extends their roaming delay and can drop calls.
The setting on the WLAN Advanced tab determines whether or not clients associating to that WLAN will be denied if the load balancing algorithm determines the AP to which the client wants to associate is too loaded (determined by the global LB settings). If you have the box unchecked, then LB is not in effect for that WLAN and clients on that WLAN will never be rejected.
The load balancing algorithm is run against clients for an AP. The count of clients is cumulative for all WLANs, i.e., the load balancing numbers are not set and comared on a per-WLAN basis. This wouldn't make a lot of sense as the LB algorithm is attempting to keep clients physically spread across infrastructure radio resources, regardless of whether you have 1 WLAN or 5 WLANs active on the radio.
I don't know of a best practices guidefor load balancing other than don't use it on WLANs that have low-latency applications such as voice or live-streaming (unbuffered) video. The controller configuration guide is a good place to start and does a pretty good job of explaining how it works.
One other thing I would recommend is to make the algorithm less aggressive. I think max 3 denials is too high and would drop to 1 or 2. I'd also open up the LB window size to about 8 or 10 instead of the default 5.
I think some folks on the forums here have found some issues with LB, although I haven't run into too many so far. I think the AP sends a message type 17 and some clients have trouble processing it (or something like that). You might want to search the forums here and check the bug toolkit to see if there's anything that comes up.
Justin
