Ignore b at your own risk
When you disable the protection mechanism of draft-11g products, you don't lose the ability to "hear" 802.11b clients, just the ability to understand them. Again using the language analogy, if everyone in a room speaks only Swedish and someone comes in speaking Flemish, although everyone will hear the person, no one will understand what he or she is saying. If the person speaks long and or loudly enough, they will interfere with conversation, and maybe even be able to stop it.
Figure 8: Linksys in "G-only" mode - WAB501 trying to associate
(click on the image for a full-sized view)
Figure 8 shows the results of an experiment that I ran using the Linksys WRT54G router and WPC54G CardBus card. I started a Chariot run between the two Linksys products, with the WRT54G set to its "G-only" mode. In another laptop sitting close by, I had a NETGEAR WAB501 Dual-Band CardBus card (Atheros based) sitting idle, scanning for a network to associate with.
The plot clearly shows an effect on the Linksys pair's throughput from an 11b client that isn't even really active, but just sending the messages it needs to try to find a network to join with. Simply put, with protection disabled, 802.11b clients become just like any other 2.4GHz noise source and can interfere with your 802.11g WLAN's transmissions.
I ran experiments with four different clients, and ran the same experiments on the Buffalo Tech gear. Although the Buffalo Tech's normal throughput "hop" makes the effect a little harder to see, a similar effect was still present.
KEY POINT #3: The performance of all 802.11g equipment, whether draft or released, can be negatively affected when you turn off the 802.11b protection mechanism and 802.11b clients are present.
I hope that 11g vendors drop the idea of calling the protection-disabled mode "Turbo", or even "G-only". But I suppose "11b Protection disabled" isn't really that sexy, is it?
So now that you know some of the technical "gotchas" of draft-11g products, it's time to come up for air and see what it all means.