What action is taken automatically by 802.11 APs and client STAs as the signal strength of the link weakens in order to improve the quality of the RF communications overall?

You are attempting to work through a user complaint with the CWNP-recommended troubleshooting methodology. What must be clearly identified in order to reduce the number of possible causes at step three?

You are troubleshooting a connection problem with a client STA. Regardless of the AP to which it attempts to connect, the connection fails. Using a wired protocol analyzer, you determine that the problem is with the 802.1X/EAP authentication to the RADIUS server. What layer or range of layers of the OSI model revealed this information?

iPerf is a tool used in what category of testing?