The RSN (Robust Security Network) Information Element (IE) is used to advertise the security capabilities of a wireless network, particularly for WPA2 and WPA3 networks. This RSN IE is contained in Beacon and Probe Response management frames, not in Probe Request, RTS, CTS, or Data frames. The Beacon frame is sent periodically by an AP to announce its presence and includes critical information about the BSS, including security settings like the RSN IE.

You would use a protocol analyzer to capture Beacon frames and inspect the RSN IE field to confirm if a BSS is properly configured to use RSN protections such as WPA2-Enterprise or WPA2-Personal.