Protection is required when 11b-only stations are present in a b/g/n network because they can't decode the header of 11g/n frames. The AP then indicates that stations should use 11b protection mode (see screenshot). The GS2K will transmit an RTS/CTS before each data frame. Stations transmitting at g/n rates transmit RTS/CTS to protect against 11b-only stations stepping on g/n transmissions. 11b-only stations can decode RTS/CTS frames, which are sent at b rates, and remain silent for the for the NAV period indicated in these frames. 11b-only stations don't do protection because they don't know about or transmit at g/n rates. This is why the GS1011 doesn't do this.
