interesting. we locked down to 1,2 for two reasons. One, it seems to work well as a built in rate limiter. Two, when we set to 11, pings sometimes go haywire, and in some cases >2miles, we start to see reregistrations. Does that make sense to you?
Frag thresh: 2346
It works as a rate limiter, since you are making every byte take 5.5-11 times as much spectrum-time. It's much better to rate-limit at a higher layer, since you would now be freeing up the extra spectrum-time.
At a 1Mbps rate, you can move at most 1Mbit in 1second. The channel is ocupied for the entire second, though. Nothing else can be done.
At a 11Mbps rate, that same 1Mbit only occupies the channel 1/11th of a second. Leaving the remaining 10/11ths for other data.
As for the funky pings, and re-registrations, yes it makes sense. It is more difficult to get a stable 11Mbps signal, than it is to get a stable 1Mbps signal (which is why they put the option in the 802.11 spec to begin with). Essentially, this works out to a SNR requirement, 11Mbps needs a better SNR than 1Mbps does.
Unfortunately, like amps, low modulations can be difficult to get rid of, even when they are crippling your network. If you install a customer, who works fine with a 1Mbps signal (and a sub 15 SNR, or so), there is a good chance that customer will not be stable at 11Mbps, without a CPE replacement and/or upgrade.
We used to allow the system to select it's own data rate, but that did nothing but cause trouble. For the last couple of years, we have been locking everyone on 802.11b to 11Mbps, and the APs where everything is purely 11Mbps perform MUCH better (some have more than 100 customers on them, with very few problems). We have been reworking the old systems, and at this point we have probably replaced 300 CPEs due to this.
Once an AP has been locked down, we can commonly get 5 times as many customers on it as before, and see a significant reduction in complaints.
We will no longer take a customer on 802.11b if they cannot sustain a stable 11Mbps signal, the damage they would do to the network far outweighs any benefit of having them as a customer. If a customer has already been installed, and already has the best 802.11b radio/antenna combo; then we refund their installation cost, reclaim the gear, say sorry, and try to get them on another system (Polling wireless, DSL, FR, etc...). Somtimes we just have to give up on the customer entirely, but it's better to lose one customer, than it is to have fifty angry ones.