CWS CWS Wi-Fi Service Sets 5 — Questions and Answers
Question 1: Which IEEE amendment introduced the Mesh Basic Service Set (MBSS) and mesh networking standards?
- 802.11n
- 802.11ac
- 802.11s (Correct answer)
- 802.11r
Correct 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.
Question 2: What is the key characteristic that distinguishes a BSS from an IBSS?
- BSS requires WPA3; IBSS does not
- BSS uses an AP as the central coordinator; IBSS has no AP (Correct answer)
- BSS operates on 5 GHz; IBSS operates on 2.4 GHz
- BSS supports only one client; IBSS supports multiple
Correct 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.
Question 3: 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?
- BSSID
- Channel number
- SSID
- Security cipher suite and SSID (Correct answer)
Correct 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.
Question 4: What does it mean when an AP advertises multiple BSSIDs from the same physical radio?
- The AP is operating in IBSS mode
- The AP is supporting multiple SSIDs, each with its own virtual BSS (Correct answer)
- The AP has multiple physical radios sharing one antenna
- The AP is acting as a mesh portal
Correct 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.
Question 5: An 802.11 client in power-save mode relies on which beacon-carried information to know when buffered frames await pickup?
- SSID element
- TIM (Traffic Indication Map) (Correct answer)
- RSN element
- DS Parameter Set
Correct 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.
Question 6: What term describes the geographic area covered by all the overlapping BSSes in an ESS?
- BSA
- ESA (Correct answer)
- DS zone
- MBSS footprint
Correct answer: ESA
The Extended Service Area (ESA) is the total coverage area formed by all the overlapping BSAs of the APs in an ESS.
Question 7: 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?
- Address 1 (DA)
- Address 2 (SA)
- Address 3 (BSSID) (Correct answer)
- Address 4
Correct 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.
CWS CWS Wi-Fi Service Sets 5
Which IEEE amendment introduced the Mesh Basic Service Set (MBSS) and mesh networking standards?