As with all things, the answers to these questions are well… it depends. When 802.11g was introduced to the market, there was a significant contribution to the backwards compatibility strategy with 802.11b networks. The same effort and differentiation is in place for coexistence of 802.11g and 802.11n networks.
To ensure that the 802.11n networks would coexist with legacy devices, the IEEE has created 3 sets of backward compatibility protection mechanisms. For a little light reading you can review the IEEE standards about signaling and 802.11n backwards compatibility protection mechanisms. But I have provided a high level summary here:
- L-SIG TXOP protection
- RTS/CTS frame exchange or CTS frame transmission
- Transmission rates: In mixed mode environments, there is a physical transmission rate protection that makes the 802.11n network transmit at 40 MHz.
To answer your last question first depends on the vendor you choose for your access points (APs). Many vendors have implemented the reporting of connections at their discretion. You would want to evaluate the vendor of choice for their visibility. In mixed mode environments, it should be imperative that you have the ability to see which users are connected at the various frequencies for troubleshooting purposes.
View our wireless expert's response to this question: Wireless networking problems combining 802.11n and 802.11g APs cause
This was first published in October 2008