
[2023年10月13日] 問題集お試しセットCWAP-404テストエンジントレーニング問題集には62問あります
CWNP CWAP-404問題集で100%カバー率リアル試験問題
質問 # 28
Which one of the following portions of information is communicated by bits in the PHY Header?
- A. Data rate
- B. Noise
- C. SNR
- D. Signal strength
正解:A
解説:
Explanation
One of the information that is communicated by bits in the PHY header is data rate. Data rate is the speed at which data is transmitted or received over the wireless medium. Data rate depends on factors such as modulation, coding, channel width, spatial streams, and guard interval. Data rate is indicated by bits in different fields of the PHY header, depending on the type of PPDU (e.g., OFDM, HT, VHT, HE). The receiver uses these bits to determine how to decode and demodulate the rest of the PPDU. The other options are not correct, as they are not communicated by bits in the PHY header. SNR (Signal-to-Noise Ratio), noise, and signal strengthare measured by the receiver based on its own capabilities and environment. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 4: 802.11 Physical Layer, page 101-105
質問 # 29
Why would a STA that supports 802.11k Radio Measurement send a Neighbor Request to an AP?
- A. To learn about neighboring interference sources and tune its RF radio accordingly
- B. To request a list of neighboring APs which the STA can use as roaming candidates
- C. To inform the current AP about the STA's intent to roam to a neighboring AP, ensuring a seamless handover
- D. To request a list of neighboring STAs which enables the STA to better pick the right protection mechanisms
正解:B
解説:
Explanation
A STA that supports 802.11k Radio Measurement would send a Neighbor Request to an AP to request a list of neighboring APs which the STA can use as roaming candidates. A Neighbor Request is an Action frame that contains a subelement specifying the type of information that the STA wants to receive from the AP. A Neighbor Report is an Action frame that contains a subelement with a list of neighboring APs that match the criteria specified in the Neighbor Request. The Neighbor Report provides information such as BSSID, channel, operating class, and PHY type of each neighboring AP. This information helps the STA to perform intelligent roaming decisions based on signal quality, load, and compatibility . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 12: 802.11k/v/r/u/w/ai Amendments, page 434; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 12: 802.11k/v/r/u/w/ai Amendments, page 435.
質問 # 30
Using a portable analyzer you perform a packet capture next to a client STA and you can see that the STA is associated to a BSS. You observe the STA sending packets to the AP and the AP sending packets to the STA.
Less than 2% of all packets are retransmissions. You move to capture packets by the AP and, while the retry rate is still less than 2%, you now only see unidirectional traffic from the AP to the client. How do you explain this behavior?
- A. There is a transmit power mismatch between the client and the AP and while the client can hear the APs traffic, the AP cannot hear the client
- B. The STA is transmitting data using more spatial streams than the potable analyzer can support
- C. The portable analyzer is too close to the AP causing CCI, blinding the AP to the clients packets
- D. The portable analyzer has a lower receive sensitivity than the AP and while it can't capture the packets from the client STA, the AP can receive them OK
正解:D
解説:
Explanation
Receive sensitivity is the minimum signal level that a receiver can detect and decode. Different devices may have different receive sensitivity levels depending on their hardware specifications and antenna configurations.
In this scenario, the portable analyzer has a lower receive sensitivity than the AP, meaning that it requires a stronger signal to capture the packets from the client STA. The AP, on the other hand, has a higher receive sensitivity and can receive the packets from the client STA even if they have a weaker signal. This explains why the portable analyzer can only see unidirectional traffic from the AP to the client when capturing near the AP5 References:
CWAP-403 Study Guide, Chapter 4: PHY Layer Analysis, page 121
CWAP-403 Objectives, Section 4.3: Analyze PHY layer metrics
質問 # 31
How many frames are exchanged for 802.11 authentication in the 6 GHz band when WPA3-Enterprise is not used, and a passphrase is used instead?
- A. 0
- B. 1
- C. 2
- D. 3
正解:B
解説:
Explanation
Two frames are exchanged for 802.11 authentication in the 6 GHz band when WPA3-Enterprise is not used, and a passphrase is used instead. Authentication is a process that establishes an identity relationship between a STA (station) and an AP (access point) before joining a BSS (Basic Service Set). There are two types of authentication methods defined by 802.11: Open System Authentication and Shared Key Authentication. Open System Authentication does not require any credentials or security information from a STA to join a BSS, and it consists of two frames: an Authentication Request frame sent by the STA to the AP, and an Authentication Response frame sent by the AP to the STA. Shared Key Authentication requires a shared secret key from a STA to join a BSS, and it consists of four frames: two challenge-response frames in addition to the request-response frames. However, Shared Key Authentication uses WEP (Wired Equivalent Privacy) as its encryption algorithm, which is insecure and deprecated. In the 6 GHz band, which is a newly available frequency band for WLANs, Shared Key Authentication is prohibited by the 802.11 standard, as it poses security and interference risks for other users and services in the band. The 6 GHz band requires all WLANs to use WPA3-Personal or WPA3-Enterprise encryption methods, which are more secure and robust than previous encryption methods such as WPA2 or WEP. WPA3-Personal uses a passphrase to derive a PMK (Pairwise Master Key), while WPA3-Enterprise uses an authentication server to obtain a PMK. Both methods use SAE (Simultaneous Authentication of Equals) as their authentication protocol, which replaces PSK (Pre-Shared Key) or EAP (Extensible Authentication Protocol). SAE consists of two frames: an SAE Commit frame sent by both parties to exchange elliptic curve parameters and nonces, and an SAE Confirm frame sent by both parties to verify each other's identities and generate a PMK. Therefore, when WPA3-Enterprise is not used, and a passphrase is used instead in the 6 GHz band, only two frames are exchanged for 802.11 authentication:
an SAECommit frame and an SAE Confirm frame. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 8: Security Analysis, page 220-221
質問 # 32
Where would you look in a packet trace file to identify the configured Minimum Basic Rate (MBR) of a BSS?
- A. In the MBR Action frame
- B. In the MBR Information Element in an Association Response frame
- C. Supported Rates & Extended Supported Rates elements in a Beacon frame
- D. In the Minimum Basic Rate Element in a Beacon frame
正解:C
解説:
Explanation
The configured Minimum Basic Rate (MBR) of a BSS can be identified by looking at the Supported Rates and Extended Supported Rates elements in a Beacon frame. A Beacon frame is a type of management frame that is transmitted by an AP to advertise its presence and capabilities to potential clients. A Beacon frame contains various information elements (IEs) that provide details about the BSS configuration and operation. The Supported Rates andExtended Supported Rates IEs list the data rates that are supported by the AP for data transmission. The MBR is the lowest data rate among these supported rates that is required for all clients to join and communicate with the BSS. The MBR is usually marked with a flag bit in these IEs to indicate its mandatory status. The other options are not correct, as they do not exist or do not indicate the MBR of a BSS. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 123-124
質問 # 33
A client is operating in an unstable RF environment. Out of five data frames transmitted to the client it only receives four. The client sends a Block Ack to acknowledge the receipt of these four frames but due to frame corruption the Block Ack is not received by the AP. Which frames will be retransmitted'
- A. Only the data frame which was corrupted
- B. Only the Block Ack
- C. Both the corrupted data and Block Ack
- D. All data frames
正解:D
解説:
Explanation
All data frames will be retransmitted in this scenario. This is because the AP uses a Block Ack (BA) mechanism to acknowledge the receipt of multiple data frames from a client in a single frame. The BA contains a bitmap that indicates which data frames were received correctly and which were not. If the BA is not received by the AP due to frame corruption, the AP will assume that none of the data frames were received by the client and will retransmit all of them. The other options are not correct, as they do not account for the loss of the BA or the use of the bitmap. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 6: 802.11 Frame Exchanges, page 167-168
質問 # 34
As a wireless network consultant you have been called in to troubleshoot a high-priority issue for one of your customers. The customer's office is based on two floors within a multi-tenant office block. On one of these floors (floor 5) users cannot connect to the wireless network. During their own testing the customer has discovered that users can connect on floor 6 but not when they move to the floor 5. This issue is affecting all users on floor 5 and having a negative effect on productivity.
To troubleshoot this issue, you perform both Spectrum and Protocol Analysis. The Spectrum Analysis shows the presence of Bluetooth signals which you have identified as coming from wireless mice. In the protocol analyzer you see the top frame on the network is Deauthentication frames. On closer investigation you see that the Deauthentication frames' source addresses match the BSSIDs of your customers APs and the destination address is FF:FF:FF:FF:FF:FF:FF.
What do you conclude from this troubleshooting exercise?
- A. The customer should replace all their Bluetooth wireless mice as they are stopping the users on floor 5 from connecting to the wireless network
- B. The customers APs are misbehaving and a technical support case should be open with the vendor
- C. The users on floor 5 are being subjected to a denial of service attack, as this is happening across the entire floor it is likely to be a misconfigured WIPS solution belonging to the tenants on the floor below
- D. The CCI from the APs on the floor 4 is the problem and you need to ask the tenant below to turn down their APs Tx power
正解:C
解説:
Explanation
The users on floor 5 are being subjected to a denial of service attack, as this is happening across the entire floor it is likely to be a misconfigured WIPS solution belonging to the tenants on the floor below. This is because the Deauthentication frames have a source address that matches the BSSIDs of the customer's APs and a destination address that is a broadcast address (FF:FF:FF:FF:FF:FF). This indicates that someone is sending spoofed Deauthentication frames to all STAs associated with the customer's APs, causing them to disconnect from the wireless network. This is a common type of DoS attack on wireless networks, and it could be caused by a rogue device or a WIPS solution that is configured to protect the wireless network of another tenant on the floor below12. References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 13: Troubleshooting Common Wi-Fi Issues, page 4961; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 14: Troubleshooting Tools, page 5272.
質問 # 35
You're the WLAN administrator for a large retailer based at the HQ in New York. The London-based office has been complaining about WLAN disconnections around lunch time each day. You suspect this might be interference from the staff microwave, how might you test your theory from the New York office?
- A. Ask a local member of staff to take some pictures of the microwave, including some close-ups of the door seal so that you can assess it
- B. Access the microwave remotely and run a diagnostic check
- C. Ask a local member of staff to change the frequency of the microwave and see if the disconnections stop
- D. Place one of the London APs into spectrum analyzer mode and monitor the situation over lunch time
正解:D
解説:
Explanation
The best way to test the theory of microwave interference from the New York office is to use a remote spectrum analyzer. By placing one of the London APs into spectrum analyzer mode, you can capture and analyze the RF spectrum in the London office over lunch time. You can then look for any signs of microwave interference, such as high duty cycle, high amplitude, or frequency hopping on the 2.4 GHz band. This method does not require any physical access tothe microwave or any changes to its frequency. References: [Wireless Analysis Professional Study Guide], Chapter 3: Spectrum Analysis, page 64
質問 # 36
What does the value of the Listen Interval field in an Association Request frame indicate?
- A. How often a STA will go off channel to look for other BSSs
- B. How long a STA performing active scanning will listen for Probe Responses before changing channels
- C. How often a STA in power save mode wakes up to listen to Beacon frames
- D. How long a STA waits for an Ack before retransmitting the frame
正解:C
解説:
Explanation
The value of the Listen Interval field in an Association Request frame indicates how often a STA in power save mode wakes up to listen to Beacon frames. The Listen Interval is expressed in units of Beacon Intervals (typically 100 TU or 102.4 ms). For example, if the Listen Interval is set to 10, it means that the STA will wake up every 10 Beacon Intervals (or about 1 second) to check for buffered frames at the AP. The Listen Interval is used by the AP to determine how long it can hold frames for a STA in power save mode before discarding them . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 197; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 198.
質問 # 37
When a data frame is encrypted with WPA2, to which portion of the frame is the encryption applied?
- A. Frame body including the LLCPDU
- B. Frame body excluding the LLCPDU
- C. Frame body and MAC Header
- D. The whole MPDU
正解:A
解説:
Explanation
When a data frame is encrypted with WPA2, the encryption is applied to the frame body including the LLCPDU. The LLCPDU (Logical Link Control Protocol Data Unit) is a part of the frame body that contains information such as protocol type, source and destination service access points (SAPs), and control fields. The LLCPDU is added by the LLC (Logical Link Control) sublayer to provide multiplexing and flow control functions for different upper layer protocols. When a data frame is encrypted with WPA2, which uses AES-CCMP as its encryption algorithm, both the payload and the LLCPDU are encrypted as a single unit. The MAC header and FCS are not encrypted, as they are needed for addressing and error detection purposes. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 115-116
質問 # 38
Given a protocol analyzer can decrypt WPA2-PSK data packets providing the PSK and SSID are configured in the analyzer software. When performing packet capture (in a non-FT environment) which frames are required in order for PSK frame decryption to be possible?
- A. 4-Way Handshake
- B. Probe Response
- C. Reassociation
- D. Authentication
正解:A
解説:
Explanation
The 4-way handshake is the process that establishes the pairwise transient key (PTK) between the client and the AP in WPA2-PSK. The PTK is derived from the PSK, the SSID, and some random numbers exchanged in the handshake frames. The PTK is used to encrypt and decrypt the data frames between the client and the AP. Therefore, in order to decrypt WPA2-PSK data packets, a protocol analyzer needs to capture the 4-way handshake frames and have the PSK and SSID configured in the analyzer software12 References:
CWAP-404 Study Guide, Chapter 3: 802.11 MAC Layer Frame Formats and Technologies, page 87 CWAP-404 Objectives, Section 3.5: Analyze security exchanges
質問 # 39
Which piece of information is not transmitted in an HT PPDU header?
- A. Channel number
- B. Number of Spatial Streams
- C. MCS index
- D. PPDU length
正解:A
解説:
Explanation
The channel number is not transmitted in an HT PPDU header. An HT PPDU header is a part of the PPDU that contains information such as modulation, coding, data rate, and number of spatial streams for an 802.11n transmission. The channel number is not included in the HT PPDU header, as it is determined by the frequency band and channel width that are used by the transmitter and receiver. The channel number can be inferred from the frequency band and channel width, which are indicated by bits in different fields of the HT PPDU header, such as HT-SIG and HT-LTF. The other options are not correct, as they are transmitted in an HT PPDU header. The number of spatial streams, PPDU length, and MCS index are indicated by bits in the HT-SIG field of the HT PPDU header. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 4: 802.11 Physical Layer, page 108-109
質問 # 40
The PHY layer provides framing by adding a header to create what type of data unit?
- A. PSDU
- B. MPDU
- C. PPDU
- D. MSDU
正解:C
解説:
Explanation
The PHY layer provides framing by adding a header to create a PPDU. A PPDU (PHY Protocol Data Unit) is the data unit that is transmitted or received over the wireless medium by the PHY layer. A PPDU consists of a PSDU (PHY Service Data Unit) and a PHY header, which contains information such as modulation, coding, and data rate. The PHY layer adds the PHY header to the PSDU to create a PPDU for transmission, or removes the PHY header from the PPDU to extract the PSDU for reception. The other options are not correct, as they are not created by adding a header at the PHY layer. An MPDU (MAC Protocol Data Unit) is created by adding a MAC header and FCS to an MSDU (MAC Service Data Unit) at the MAC layer. An MSDU is the data unit that is passed from the LLC sublayer to the MAC sublayer or vice versa. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 4: 802.11 Physical Layer, page 97-98
質問 # 41
Which one of the following is not an 802.11 Management frame?
- A. Beacon
- B. Action
- C. Authentication
- D. PS-Poll
正解:D
解説:
Explanation
A PS-Poll (Power Save Poll) frame is not an 802.11 management frame. A PS-Poll frame is a type of control frame that is used by a STA in power save mode to request data frames from an AP. A STA in power save mode can conserve battery power by periodically sleeping and waking up. When a STA sleeps, it cannot receive any data frames from the AP, so it informs the AP of its power save status by setting a bit in its MAC header. The AP then buffers any data frames destined for the sleeping STA until it wakes up. When a STA wakes up, it sends a PS-Poll frame to the AP, indicating its association ID and requesting any buffered data frames. The AP thenresponds with one or more data frames, followed by an ACK or BA frame from the STA.
The other options are not correct, as they are types of 802.11 management frames. An Action frame is used to perform various management actions, such as spectrum management, QoS management, radio measurement, etc. A Beacon frame is used to advertise the presence and capabilities of an AP or BSS. An Authentication frame is used to establish or terminate an authentication relationship between a STA and an AP. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 6: 802.11 Frame Exchanges, page 169-170
質問 # 42
ABC International has installed a new smart ZigBee controlled lighting system. However, the network team is concerned that this new system will interfere with the existing WLAN and has asked you to investigate the impact of the two systems operating simultaneously in the 2.4 GHz band. When performing Spectrum Analysis, which question could you answer by looking at the FFT plot?
- A. Is the WLAN corrupting ZigBee system messages?
- B. Is the ZigBee system causing an increase in WLAN retries?
- C. Do the ZigBee channels used by the lighting system overlap with the WLAN channels?
- D. Is the ZigBee system using more than 50% of the available airtime?
正解:C
解説:
Explanation
The FFT plot is a spectrum analysis plot that shows the RF power present at a particular frequency over a short period of time. It can help identify the sources and characteristics of RF signals in the spectrum. By looking at the FFT plot, you can determine which ZigBee channels are used by the lighting system and whether they overlap with the WLAN channels in the 2.4 GHz band. ZigBee channels are 5 MHz wide and WLAN channels are 20 MHz or 40 MHz wide, so there is a possibility of overlap and interference between them. The other questions cannot be answered by looking at the FFT plot alone, as they require other types of plots or analysis tools, such as duty cycle plot, airtime utilization plot, or protocol analyzer. References: [Wireless Analysis Professional Study Guide], Chapter 3: Spectrum Analysis, page 69-70
質問 # 43
When configuring a long-term, forensic packet capture and saving all packets to disk which of the following is not a consideration?
- A. Individual trace file size
- B. Real-time packet decodes
- C. Total capture storage space
- D. Analyzer location
正解:B
解説:
Explanation
Real-time packet decodes are not a consideration when configuring a long-term, forensic packet capture and saving all packets to disk. Real-time packet decodes are useful for live analysis and troubleshooting, but they consume CPU and memory resources that could affect the performance of the capture process. For a long-term, forensic packet capture, it is more important to consider the analyzer location, the total capture storage space, and the individual trace file size. These factors affect the quality and quantity of the captured packets and the ease of post-capture analysis34 References:
CWAP-404 Study Guide, Chapter 2: Protocol Analysis, page 49
CWAP-404 Objectives, Section 2.1: Configure protocol analyzers
質問 # 44
In what scenario is Open Authentication without encryption not allowed based on the 802.11 standard?
- A. When operating a BSS in FIPS mode
- B. When operating a BSS in the 6 GHz band
- C. When operating a BSS in a government facility
- D. When operating a BS5 in the CBRS band
正解:B
解説:
Explanation
Open Authentication without encryption is not allowed when operating a BSS in the 6 GHz band, according to the 802.11 standard. Open Authentication is a type of authentication method that does not require any credentials or security information from a STA (station) to join a BSS (Basic Service Set). Open Authentication can be used with or without encryption, depending on the configuration of the BSS and the STA. Encryption is a technique that scrambles the data frames using an algorithm and a key to prevent unauthorized access or eavesdropping. However, in the 6 GHz band, which is a newly available frequency band for WLANs, OpenAuthentication without encryption is prohibited by the 802.11 standard, as it poses security and interference risks for other users and services in the band. The 6 GHz band requires all WLANs to use WPA3-Personal or WPA3-Enterprise encryption methods, which are more secure and robust than previous encryption methods such as WPA2 or WEP. The other options are not correct, as they do not describe scenarios where Open Authentication without encryption is not allowed by the 802.11 standard. When operating a BSS in the CBRS band, which is another newly available frequency band for WLANs, Open Authentication without encryption is allowed, but not recommended, as it also poses security and interference risks for other users and services in the band. When operating a BSS in FIPS mode, which is a mode that complies with the Federal Information Processing Standards for cryptographic security, Open Authentication without encryption is allowed, but not compliant, as it does not meet the FIPS requirements for encryption algorithms and keys. When operating a BSS in a government facility, Open Authentication without encryption is allowed, but not advisable, as it may violate the government policies or regulations for wireless security. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 8: Security Analysis, page 220-221
質問 # 45
What interframe space would be expected between a CIS and a Data frame?
- A. PIFS
- B. SIFS
- C. DIFS
- D. AIFS
正解:B
解説:
Explanation
The interframe space that would be expected between a CTS (Clear to Send) and a Data frame is SIFS (Short Interframe Space). A SIFS is the shortest interframe space that is used for high-priority transmissions, such as ACKs (Acknowledgements), CTSs, or data frames that are part of a fragmentation or aggregation process. A SIFS is a fixed value that depends on the PHY type and channel width. A CTS and a Data frame are part of a virtual carrier sense mechanism called RTS/CTS (Request to Send/Clear to Send), which is used to avoid collisions and hidden node problems in wireless transmissions. When a STA (station) wants to send a data frame, it first sends an RTS frame to the intended receiver, indicating the duration of the transmission. The receiver then responds with a CTS frame, also indicating the duration of the transmission. The other STAs in the vicinity hear either the RTS or the CTS frame and update their NAV (Network Allocation Vector) timers accordingly, deferring their access to the medium until the transmission is over. The sender then sends the data frame after waiting for a SIFS, followed by an ACK frame from the receiver after another SIFS. The other options are not correct, as they are not used between a CTS and a Data frame. A PIFS (PCF Interframe Space) is used for medium access by the PCF (Point Coordination Function), which is an optional and rarely implemented polling-based mechanism that provides contention-free service for time-sensitive traffic. An AIFS (Arbitration Interframe Space) is used for medium access by different ACs (Access Categories), which are logical queues that correspond to different QoS (Quality of Service) levels for different types of traffic. An AIFS is a variable interframe space that depends on the AIFSN (Arbitration Interframe Space Number) value of each AC. A DIFS (Distributed Interframe Space) is used for medium access by the DCF (Distributed Coordination Function), which is the default and mandatory contention-based mechanism that provides best-effort service for normal traffic. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 6: 802.11 Frame Exchanges, page 166-167; Chapter 7: QoS Analysis, page 194-195
質問 # 46
After examining a Beacon frame decode you see the SSID Element has a length of 0. What do you conclude about this frame?
- A. The beacon is from a BSS configured to hide the SSID
- B. The frame is corrupted
- C. SSID elements always have a length of 0
- D. This is a common attack on WISP backend SQL databases
正解:A
解説:
Explanation
If the SSID element has a length of 0 in a Beacon frame decode, it means that the beacon is from a BSS configured to hide the SSID. The SSID element is a part of the Beacon frame that contains the name or identifier of the BSS. The SSID element has two fields: length and value. The length field indicates how many bytes are used for the value field, which contains the actual SSID string. If the length field is 0, it means that there is no value field or SSID string in the element. This is a common technique used by some APs to hide their SSID from passive scanning clients or potential attackers. However, this technique does not provide much security, as there are other ways to discover or reveal the hidden SSID, such as active scanning or capturing probe response or association frames. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 122-123
質問 # 47
Where would you look in a packet trace file to identify the configured Minimum Basic Rate (MBR) of a BSS?
- A. In the MBR Action frame
- B. In the MBR Information Element in an Association Response frame
- C. Supported Rates & Extended Supported Rates elements in a Beacon frame
- D. In the Minimum Basic Rate Element in a Beacon frame
正解:C
解説:
Explanation
The configured Minimum Basic Rate (MBR) of a BSS can be identified by looking at the Supported Rates and Extended Supported Rates elements in a Beacon frame. A Beacon frame is a type of management frame that is transmitted by an AP to advertise its presence and capabilities to potential clients. A Beacon frame contains various information elements (IEs) that provide details about the BSS configuration and operation. The Supported Rates andExtended Supported Rates IEs list the data rates that are supported by the AP for data transmission. The MBR is the lowest data rate among these supported rates that is required for all clients to join and communicate with the BSS. The MBR is usually marked with a flag bit in these IEs to indicate its mandatory status. The other options are not correct, as they do not exist or do not indicate the MBR of a BSS. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 123-124
質問 # 48
......
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