CWS Wi-Fi Service Sets Flashcards

Which IEEE amendment introduced the Mesh Basic Service Set (MBSS) and mesh networking standards?

Answer: 802.11s

IEEE 802.11s introduced the MBSS, defining how mesh points (MPs) discover each other and route frames over multi-hop wireless links.

What is the key characteristic that distinguishes a BSS from an IBSS?

Answer: BSS uses an AP as the central coordinator; IBSS has no AP

A BSS (infrastructure mode) requires an AP to coordinate all communications, while an IBSS (ad-hoc mode) has no AP and stations communicate directly.

When a roaming client re-associates from one AP to another within the same ESS, which parameter must remain the same for the roam to succeed transparently?

Answer: Security cipher suite and SSID

For a successful roam within an ESS, both the SSID and the security/encryption parameters must match across APs, while the BSSID will differ.

What does it mean when an AP advertises multiple BSSIDs from the same physical radio?

Answer: The AP is supporting multiple SSIDs, each with its own virtual BSS

When an AP supports multiple SSIDs, it creates a virtual BSS for each SSID, each with a unique BSSID derived from the AP's base MAC address.

An 802.11 client in power-save mode relies on which beacon-carried information to know when buffered frames await pickup?

Answer: TIM (Traffic Indication Map)

The Traffic Indication Map (TIM) in the beacon informs power-saving clients which of them have frames buffered at the AP awaiting retrieval.

What term describes the geographic area covered by all the overlapping BSSes in an ESS?

Answer: ESA

The Extended Service Area (ESA) is the total coverage area formed by all the overlapping BSAs of the APs in an ESS.

In the 802.11 MAC address field naming convention for a frame going from a client TO the DS (To DS=1, From DS=0), which field contains the BSSID?

Answer: Address 3 (BSSID)

In a To-DS frame (client sending to AP), Address 1 = AP MAC (RA), Address 2 = client MAC (TA/SA), and Address 3 = BSSID/destination.