CWS CWS WLAN Roaming and QoS Questions and Answers 3 — Questions and Answers
Question 1: Which 802.11 feature allows a client to request a neighbor report from its currently associated AP?
- 802.11k Neighbor Report Request (Correct answer)
- 802.11v BSS Transition Query
- 802.11r Pre-Authentication
- 802.11u GAS Request
Correct answer: 802.11k Neighbor Report Request
Under 802.11k, a client can send a Neighbor Report Request to its AP and receive a list of nearby APs to consider for roaming.
Question 2: What is the purpose of the AIFS (Arbitration Inter-Frame Space) in EDCA?
- Defines the minimum idle time before a traffic category may begin contending for the channel (Correct answer)
- Sets the maximum frame size for a burst
- Configures the encryption key refresh interval
- Determines the beacon transmission interval
Correct answer: Defines the minimum idle time before a traffic category may begin contending for the channel
AIFS determines how long a station must sense the channel idle before beginning its random backoff, with higher-priority ACs using shorter AIFS values.
Question 3: In a 802.11r over-the-air fast transition, what frames does the client use to complete the roam?
- Authentication and Reassociation frames with FT IEs (Correct answer)
- Probe and Association frames only
- EAPOL 4-way handshake frames
- Deauthentication and new Association frames
Correct answer: Authentication and Reassociation frames with FT IEs
Over-the-air FT uses modified Authentication and Reassociation frames carrying FT Information Elements to complete the handoff with a single round-trip.
Question 4: Which AC_BK (Background) traffic characteristic distinguishes it from AC_BE (Best Effort)?
- AC_BK uses a larger CWmin and longer AIFS, resulting in lower priority than AC_BE (Correct answer)
- AC_BK uses stronger encryption
- AC_BK is reserved for management frames
- AC_BK has a shorter TXOP limit than AC_VO
Correct answer: AC_BK uses a larger CWmin and longer AIFS, resulting in lower priority than AC_BE
AC_BK is configured with larger contention window parameters and a longer AIFS than AC_BE, making it the lowest-priority access category.
Question 5: What problem does load balancing address in a multi-AP WLAN deployment?
- Prevents too many clients from associating with one AP while nearby APs are underutilized (Correct answer)
- Reduces RF interference between co-channel APs
- Eliminates hidden node collisions
- Distributes DHCP leases evenly
Correct answer: Prevents too many clients from associating with one AP while nearby APs are underutilized
Load balancing distributes client associations across APs to avoid overloading a single AP and ensure consistent throughput for all clients.
Question 6: Which protocol is used by a WLAN controller to request that a client roam to a different AP under 802.11v?
- BSS Transition Management Request (Correct answer)
- RADIUS Change of Authorization
- EAP Re-Authentication Protocol
- DHCP Inform
Correct answer: BSS Transition Management Request
The BSS Transition Management Request frame (802.11v) is sent by the AP/controller to suggest or require a client to roam to a specified target AP.
CWS CWS WLAN Roaming and QoS Questions and Answers 3
Which 802.11 feature allows a client to request a neighbor report from its currently associated AP?