WLAN Protocols, Standards and Operations
The standard family
802.11a (5 GHz OFDM), b (2.4 GHz DSSS), g (2.4 GHz OFDM), n (2.4/5 GHz, MIMO, 40 MHz), ac (5 GHz only, up to 80/160 MHz, MU-MIMO downlink), ax (2.4/5/6 GHz, OFDMA, BSS coloring, TWT, uplink and downlink MU-MIMO) and be (MLO, wider channels) form the progression. Remember that 802.11ac is 5 GHz only and that 6 GHz operation begins with Wi-Fi 6E.
Frames and exchanges
Management frames (beacon, probe request/response, authentication, association, deauthentication) build and tear down relationships; control frames (RTS/CTS, ACK, block ACK) manage the medium; data frames carry traffic. Beacons default to roughly 100 ms intervals and advertise capabilities and rates. The 4-way handshake follows open authentication and association. The 802.11 amendments to know: i for security, e/WMM for QoS, h for DFS and TPC, k for neighbor reports, v for BSS transition management, r for fast BSS transition, w for management frame protection, s for mesh.
Operations
Infrastructure questions often cover PoE budgets (802.3af roughly 15.4 W at the port, at up to 30 W, bt up to about 60–90 W), controller architectures (centralized, cloud, embedded), CAPWAP/LWAPP tunnels, 802.1Q trunking to APs, regulatory domains and DFS channels, NTP and syslog for correlation, and firmware lifecycle management.
Traps
Do not confuse 802.11k (neighbor reports), 802.11v (steering/BSS transition requests) and 802.11r (fast transition key caching). Do not assume a beacon interval of exactly 100 ms - it is commonly 102.4 ms in practice. Do not assume higher PHY rates apply across all bands.
Rule of thumb
When a question describes a client refusing to roam, look for missing 802.11k/v/r support and poor cell overlap before blaming the client driver.