What ID is typically mapped to an AP's MAC address if a single BSS is implemented?
Answer(s): D
The BSSID (Basic Service Set Identifier) is typically mapped to an AP's MAC address if a single BSS is implemented. The BSSID is a unique identifier that distinguishes one BSS from another within the same RF medium. It is usually derived from the MAC address of the AP's radio interface, but it can also be manually configured or randomly generated by some vendors. The BSSID is used by client stations to associate with an AP and to send and receive frames within a BSS.
Chapter 1, page 24; , Section 1.2
What is appended to the end of each 802.11 data frame after the payload?
The FCS (Frame Check Sequence) is appended to the end of each 802.11 data frame after the payload. The FCS is a 4-byte field that contains a CRC-32 (Cyclic Redundancy Check) value that is calculated based on the contents of the MAC header and the payload of the frame. The FCS is used by the receiver to verify the integrity of the frame and to detect any errors or corruption that may have occurred during transmission. If the FCS does not match with the expected value, the frame is discarded by the receiver.
Chapter 4, page 139; , Section 4.2
When an ACK frame is not received by the transmitting STA, what is assumed?
Answer(s): C
An ACK (Acknowledgement) frame is a short control frame that is sent by the receiver of a data or management frame to confirm that the frame was received correctly. The ACK frame is sent after a SIFS (Short Interframe Space) interval, which is the shortest time gap between frames in 802.11. If the transmitter does not receive an ACK frame within a specified time, it assumes that the frame was not delivered and must be retransmitted. This is part of the 802.11 reliability mechanism that ensures reliable data delivery over an unreliable wireless medium .
[CWNA-109 Study Guide], Chapter 5: IEEE 802.11 Medium Access, page 209; [CWNA-109 Study Guide], Chapter 5: IEEE 802.11 Medium Access, page 203.
When a client station sends a broadcast probe request frame with a wildcard SSID, how do APs respond?
Answer(s): A
In the 802.11 wireless networking protocols, when a client station sends a broadcast probe request frame with a wildcard SSID (Service Set Identifier), it is essentially asking for any nearby access points (APs) to identify themselves. The way APs respond to such a probe request is governed by standard 802.11 behavior, which includes:Probe Request Handling: Upon receiving a broadcast probe request, each AP that can serve the client prepares a probe response. The response includes information about the AP, such as its SSID, supported data rates, and other capabilities.Contention-Based Mechanism: Wireless networks use a contention-based mechanism (CSMA/CA - Carrier Sense Multiple Access with Collision Avoidance) for medium access. Each AP must wait for a clear channel and win the contention process before it can send its probe response. Independent Responses: Each AP operates independently in responding to the probe request. There is no coordination between APs to decide which one responds first or at all, leading to multiple APs sending probe responses, each after winning the contention for the medium. Option A accurately reflects this process, indicating that each AP prepares and sends a probe response in turn, contingent upon winning the medium contention. The other options suggest mechanisms (such as coordination with a DHCP server or simultaneous responses after a Short Interframe Space (SIFS)) that do not align with standard 802.11 procedures for handling broadcast probe requests.
IEEE 802.11 Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. CWNA Certified Wireless Network Administrator Official Study Guide: Exam PW0-105, by David D.Coleman and David A. Westcott.
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Quentin commented on November 14, 2024 I noticed that some comments were related to answers not being 100% correct. But for me as long as questions are real and same as the actual exam I was okay. Mexico upvote
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