合格できるCWNP CWAP-404のPDF問題集！最近更新された62問あります [Q31-Q52]

合格できるCWNP CWAP-404のPDF問題集！最近更新された62問あります

更新されたテストエンジンCWAP-404練習問題集と練習試験合格させます

質問 # 31
Which one of the following is not an 802.11 Management frame?

A. Action
B. Beacon
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 # 32
An RTS frame should be acknowledged by which frame?

A. Ack
B. RTS-Ack
C. Block Ack
D. CTS

正解：D

解説：
Explanation
An RTS (Request to Send) frame should be acknowledged by a CTS (Clear to Send) frame. An RTS and CTS frame are types of control frames that are used to implement a virtual carrier sense mechanism called RTS/CTS. RTS/CTS is a technique that helps 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, followed by an ACK (Acknowledgement) frame from the receiver. The other options are not correct, as they are not used to acknowledge an RTS frame. An ACK frame is used to acknowledge a data frame, not an RTS frame. An RTS-Ack frame does not exist, as there is no such type of control frame in 802.11. A Block Ack (BA) frame is used to acknowledge multiple data frames in a single frame, not an RTS frame. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 6: 802.11 Frame Exchanges, page 166-167

質問 # 33
802.11k Neighbor Requests and Neighbor Reports are sent in what type of Management Frames?

A. Reassociation Request and Reassociation Response
B. Beacon
C. RRM
D. Action

正解：D

解説：
Explanation
802.11k Neighbor Requests and Neighbor Reports are sent in Action frames. An Action frame is a Management frame that is used to perform various operations or functions related to the operation or maintenance of a wireless network. An Action frame consists of a Category field that indicates the type of action being performed, and a variable-length Action Details field that contains specific information related to the action. For example, an Action frame with a Category field value of 5 indicates a Radio Measurement action, and the Action Details field may contain a Neighbor Request or a Neighbor Report subelement .
References: CWAP-404 CertifiedWireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 207; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 208; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 12: 802.11k/v/r/u/w/ai Amendments, page 434.

質問 # 34
You have installed a new 802.1 lac WLAN configured with 80 MHz channels. Users in one area are complaining about poor performance. This area is currently served by a single AP. You take a spectrum analysis capture in the poor performing area. While examining the waterfall plot you notice the airtime utilization is higher on the first 20 MHz of the 80 MHz channel when compared to the rest of the channel.
What do you conclude?

A. The first 20 MHz is the AP's primary channel and higher airtime utilization on the primary channel is normal when an AP is configured for 80 MHz operation
B. Non-Wi-Fi interference is preventing the APs 80 MHz operation
C. RRM is enabled and has dynamically picked a 20 MHz channel
D. The AP is misconfigured and needs to be reconfigured to 80 MHz operation

正解：B

解説：
Explanation
The most likely cause of higher airtime utilization on the first 20 MHz of the 80 MHz channel is non-Wi-Fi interference. Non-Wi-Fi interference can prevent an AP from using its full channel width, as it will degrade the signal quality and increase the noise floor on some parts of the channel. This will force the AP to fall back to a narrower channel width, such as 20 MHz or 40 MHz, to maintain communication with its clients. The waterfall plot can help identify non-Wi-Fi interference by showing spikes or bursts of RF energy on specific frequencies or sub-channels. The other options are not correct, as they do not explain why only the first 20 MHz of the channel has higher airtime utilization. References: [Wireless Analysis Professional Study Guide], Chapter 3: Spectrum Analysis, page 74-75

質問 # 35
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. Do the ZigBee channels used by the lighting system overlap with the WLAN channels?
B. Is the ZigBee system using more than 50% of the available airtime?
C. Is the ZigBee system causing an increase in WLAN retries?
D. Is the WLAN corrupting ZigBee system messages?

正解：A

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 # 36
What is an AIFS?

A. The shortest period of time a STA can sleep
B. A medium access method introduced by 802.lln, but never implemented
C. A form of aggregation performed at the PHY layer based on 802.lie UP values interpreted from DSCP values
D. A variable Interframe Space introduced by 802.lie to help prioritize medium access for different Access Categories

正解：D

解説：
Explanation
An AIFS is a variable interframe space introduced by 802.11e to help prioritize medium access for different Access Categories (ACs). An interframe space is a period of time that a STA (station) has to wait before attempting to access the medium. An AIFS is a type of interframe space that varies depending on the AC of the traffic. An AC is a logical queue that corresponds to a QoS (Quality of Service) level for different types of traffic. There are four ACs defined by 802.11e: AC_VO (Voice), AC_VI (Video), AC_BE (Best Effort), and AC_BK (Background). Each AC has a different AIFSN (Arbitration Interframe Space Number) value, which determines how long it has to wait before attempting to access the medium. A lower AIFSN value means a higher priority and a shorter waiting time. The other options are not correct, as they do not describe what an AIFS is. An AIFS is not a medium access method introduced by 802.11n, but never implemented, as it is part of the 802.11e standard and widely used in QoS-enabled WLANs. An AIFS is not a form of aggregation performed at the PHY layer based on 802.11e UP values interpreted from DSCP values, as aggregation is a technique that combines multiple frames into one larger frame to improve efficiency and throughput, not prioritization or medium access. An AIFS is not the shortest period of time a STA can sleep, as sleeping is a power saving mode that allows a STA to conserve battery power by periodically turning off its radio, not accessing the medium. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 7: QoS Analysis, page 194-195

質問 # 37
The PHY layer provides framing by adding a header to create what type of data unit?

A. MSDU
B. PPDU
C. PSDU
D. MPDU

正解：B

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 # 38
In what scenario is Open Authentication without encryption not allowed based on the 802.11 standard?

A. When operating a BS5 in the CBRS band
B. When operating a BSS in the 6 GHz band
C. When operating a BSS in FIPS mode
D. When operating a BSS in a government facility

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 # 39
What is used to respond with an uplink transmission to an MU-RTS trigger frame in the 802.11ax PHY?

A. HE MU PPDU
B. HE SU PPDU
C. VHT PPDU
D. HE TB PPDU

正解：D

解説：
Explanation
An HE TB PPDU (High Efficiency Trigger-Based Packet Data Unit) is used to respond with an uplink transmission to an MU-RTS trigger frame in the 802.11ax PHY (Physical Layer). An MU-RTS trigger frame is a frame that initiates a multi-user transmission opportunity (MU-TXOP) by requesting multiple stations (STAs) to send clear-to-send (CTS) frames on different spatial streams or resource units (RUs). An HE TB PPDU is a frame that contains data from multiple STAs that have been allocated RUs by an MU-RTS trigger frame or another type of trigger frame. An HE SU PPDU (High Efficiency Single User Packet Data Unit) is a frame that contains data from a single STA using all available spatial streams or RUs. An HE MU PPDU (High Efficiency Multi User Packet Data Unit) is a frame that contains data from multiple STAs using different spatial streams or RUs without being triggered by another frame. A VHT PPDU (Very High Throughput Packet Data Unit) is a frame that uses the 802.11ac PHY and does not support multi-user transmissions.References:
CWAP-404 Study Guide, Chapter 3: 802.11 MAC Layer Frame Formats and Technologies, page 101 CWAP-404 Objectives, Section 3.4: Analyze multi-user transmissions CWAP-404 Study Guide, Chapter 3: 802.11 MAC Layer Frame Formats and Technologies, page 99

質問 # 40
Where would you look in a packet trace file to identify the configured Minimum Basic Rate (MBR) of a BSS?

A. In the Minimum Basic Rate Element in a Beacon 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 MBR Action 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 # 41
Which one of the following should be the first step when troubleshooting a WLAN issue?

A. Perform an initial WLAN scan and see if any obvious issues stand out
B. Define the problem
C. Identify probable causes
D. Identify capture locations

正解：B

解説：
Explanation
The first step in any troubleshooting process is to define the problem. This involves gathering information from various sources, such as users, network administrators, network documentation, and network monitoring tools. Defining the problem helps to narrow down the scope of the issue and identify the symptoms, causes, and effects of the problem12 References:
CWAP-403 Study Guide, Chapter 1: Troubleshooting Methodology, page 7
CWAP-403 Objectives, Section 1.1: Define the problem

質問 # 42
You are performing a multiple adapter channel aggregation capture to troubleshoot a VoIP roaming problem and would like to measure the roaming time from the last VoIP packet sent on the old AP's channel to the first VoIP packet sent on the new AP's channel. Which timing column in the packet view would measure this for you?

A. Relative
B. Roaming
C. Delta
D. Absolute

正解：C

解説：
Explanation
Delta is the timing column in the packet view that measures the time difference between two consecutive packets in a capture file. Delta can be used to measure the roaming time from the last VoIP packet sent on the old AP's channel to the first VoIP packet sent on the new AP's channel by selecting these two packets and looking at their delta values. The other timing columns are not suitable for this measurement because they do not show the time difference between two specific packets. Roaming is a column that shows whether a packet belongs to a roaming event or not. Relative is a column that shows the time elapsed since the beginning of the capture file. Absolute is a column that shows the date and time when a packet was captured5 References:
CWAP-404 Study Guide, Chapter 2: Protocol Analysis, page 57
CWAP-404 Objectives, Section 2.4: Analyze timing values

質問 # 43
What is the function of 802.11 Management frames?

A. Prioritize network administration traffic
B. Communicate configuration changes between WLAN controller and APs
C. Manage the BSS
D. Manage the flow of data

正解：C

解説：
Explanation
The function of 802.11 management frames is to manage the BSS. A BSS (Basic Service Set) is a group of STAs (stations) that share a common SSID (Service Set Identifier) and communicate with each other through an AP (access point) or directly in an ad hoc mode. Management frames are one of the three types of 802.11 frames, along with control and data frames. Management frames are used to establish, maintain, and terminate associations between STAs and APs, as well as to advertise and discover BSSs, exchange security information, report errors, and perform other management functions. The other options are not correct, as they are not functions of 802.11 management frames. Prioritizing network administration traffic, communicating configuration changes between WLAN controller and APs, and managing the flow of data are functions of other types of frames or protocols. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 120-121

質問 # 44
What is the function of the PHY Preamble?

A. Carries the NDP used in Transmit Beamforming and MU-MIMO
B. To set the modulation method for the MPDU
C. Allows the receiver to detect and synchronize with the signal
D. To terminate a conversation between transmitter and receiver

正解：C

解説：
Explanation
The function of the PHY preamble is to allow the receiver to detect and synchronize with the signal. The PHY preamble is a part of the PPDU that is transmitted before the PHY header and the PSDU. The PHY preamble consists of a series of training fields that help the receiver to adjust its parameters, such as frequency, timing, and gain, to match the incoming signal. The PHY preamble also helps the receiver to estimate the channel conditions and noise level. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 4:
802.11 Physical Layer, page 99-100

質問 # 45
Which one of the statements regarding the Frame Control field in an 802.11 MAC header is true?

A. The Frame Control field is always set to 0
B. The Frame Control field is used to communicate the duration value
C. The Frame Control field contains subfields, and soma in 1-bit flags
D. Only Control frames have a Frame Control field

正解：C

解説：
Explanation
The statement that the Frame Control field contains subfields, and some 1-bit flags is true. The Frame Control field is a 2-byte field in the MAC header that contains information about the type, subtype, and characteristics of a frame. The Frame Control field is divided into several subfields, each with a specific function and length.
Some of these subfields are 1-bit flags, which can be set to 0 or 1 to indicate a certain condition or status. For example, the To DS and From DS subfields are 1-bit flags that indicate whether a frame is destined for or originated from the DS (Distribution System). The other statements are not true, as they do not describe the Frame Control field correctly. All types of frames (management, control, and data) have a Frame Control field, not just control frames. The Frame Control field is not used to communicate the duration value, which is a separate field in the MAC header. The Frame Control field is not always set to 0, as it varies depending on the type, subtype, and characteristics of each frame. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 113-114

質問 # 46
The network administrator at ABC Engineering has taken a large packet capture from one of their APs running in monitor mode. She has very little knowledge of 802.11 protocols but would like to use the capture file to evaluate the overall health and performance of their wireless network. When she asks your advice, which tool do you recommend she opens the packet capture file with?

A. Spectrum analyzer
B. Capture visualization tool
C. Python
D. WLAN scanner

正解：B

解説：
Explanation
A capture visualization tool is a software application that can open a packet capture file and display various graphs, charts, tables, and statistics that illustrate the characteristics and behavior of the wireless network. A capture visualization tool can help a network administrator with little knowledge of 802.11 protocols to evaluate the overall health and performance of their wireless network by providing a visual and intuitive representation of the captured data. A spectrum analyzer is a hardware device that measures the radio frequency signals in a given frequency range and displays their amplitude, frequency, and modulation. A spectrum analyzer can help identify sources of interference and noise in the wireless environment, but it cannot open a packet capture file. Python is a programming language that can be used to write scripts or applications that manipulate or analyze packet capture files, but it requires coding skills and knowledge of
802.11 protocols. A WLAN scanner is a software application that scans for available wireless networks and displays information such as SSID, BSSID, channel, signal strength, security type, and vendor. A WLAN scanner can help discover wireless networks and their basic parameters, but it cannot open a packet capture file345 References:
CWAP-404 Study Guide, Chapter 2: Protocol Analysis, page 63
CWAP-404 Objectives, Section 2.5: Use capture visualization tools
CWAP-404 Study Guide, Chapter 4: Spectrum Analysis and Troubleshooting, page 117 CWAP-404 Objectives, Section 4.1: Use spectrum analysis tools CWAP-404 Study Guide, Chapter 2: Protocol Analysis, page 33 CWAP-404 Objectives, Section 2.2: Analyze field values

質問 # 47
A manufacturing facility has installed a new automation system which incorporates an 802.11 wireless network. The automation system is controlled from tablet computers connected via the WLAN. However, the automation system has not gone live due to problem with the tablets connecting to the WLAN. The WLAN vendor has been onsite to perform a survey and confirmed good primary and secondary coverage across the facility. As a CWAP you are called in to perform Spectrum Analysis to identify any interference sources.
From the spectrum analysis, you did not identify any interference sources but were able to correctly identify the issue. Which of the following issues did you identify from the spectrum analysis?

A. The tablets are entering power save mode and failing to wake up to receive the access points transmissions
B. There is a power mismatch between the APs and the clients
C. A high noise floor has resulted in a SNR of less than 20dB
D. The tablets are connecting to the wrong SSID

正解：B

解説：
Explanation
The most likely issue that can be identified from the spectrum analysis is a power mismatch between the APs and the clients. A power mismatch occurs when the APs transmit at a higher power level than the clients, or vice versa. This can cause asymmetric communication, where one side can hear the other, but not vice versa.
This can result in poor performance, disconnections, or packet loss. A spectrum analysis can reveal a power mismatch by showing different signal amplitudes or RSSI values for the APs and the clients on the same channel or frequency. The other options are not correct, as they cannot be identified from the spectrum analysis alone. The tablets' SSID, power save mode, and noise floor can be determined by using other tools or methods, such as protocol analysis, site survey, or device configuration. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 3: Spectrum Analysis, page 79-80

質問 # 48
The PHY layer provides framing by adding a header to create what type of data unit?

A. MSDU
B. PPDU
C. PSDU
D. MPDU

正解：B

質問 # 49
Which piece of information is not transmitted in an HT PPDU header?

A. PPDU length
B. Number of Spatial Streams
C. MCS index
D. Channel number

正解：D

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 # 50
What interframe space would be expected between a CIS and a Data frame?

A. PIFS
B. SIFS
C. AIFS
D. DIFS

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 # 51
When performing protocol analysis, you notice a high number of RTS/CTS frames being transmitted on an HT network. You suspect this may be due to HT protection mechanisms. Where in the Beacon frame would you look to determine which one of the four HT protection modes the AP is operating in?

A. HT Operation Element
B. HT Protection Element
C. Non-HT Present Element
D. HT Information Element

正解：D

解説：
Explanation
When performing protocol analysis, you would look at the HT Information Element in the Beacon frame to determine which one of the four HT protection modes the AP is operating in. The HT Information Element contains various subfields that provide information about the HT network configuration and operation. One of these subfields is the HT Protection field, which indicates whether any protection mechanisms are required for mixed-mode operation with non-HT STAs. The four possible values for this field are:
No Protection: No protection mechanisms are required.
Non-member Protection: RTS/CTS or CTS-to-self protection is required for all HT transmissions.
20 MHz Protection: RTS/CTS or CTS-to-self protection is required for all HT transmissions using a 40 MHz channel.
Non-HT Mixed Mode: All HT transmissions must use a non-HT preamble and header . References:
CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 11:
802.11n/ac/ax PHYsical Layer Frame Exchanges, page 378; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 11: 802.11n/ac/ax PHYsical Layer Frame Exchanges, page 379.

質問 # 52
......

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