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CWNP CWAP-404 Exam Certification Details:
| Passing Score | 70% |
| Recommended Training | CWAP self-paced training kit, Training Class |
| Duration | 90 minutes |
| Exam Name | Wireless Analysis Professional |
| Exam Price | $275 USD |
| Exam Code | CWAP-404 CWAP |
| Exam Registration | PEARSON VUE |
NEW QUESTION # 32
Which piece of information is not transmitted in an HT PPDU header?
- A. PPDU length
- B. MCS index
- C. Channel number
- D. Number of Spatial Streams
Answer: C
Explanation:
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
NEW QUESTION # 33
In the 2.4 GHZ band, what data rate are Probe Requests usually sent at from an unassociated STA?
- A. The minimum basic rate
- B. MCS 0
- C. 6 Mbps
- D. 1 Mbps
Answer: A
Explanation:
Explanation
In the 2.4 GHz band, probe requests are usually sent at the minimum basic rate from an unassociated STA. A probe request is a type of management frame that is transmitted by a STA to discover available BSSs in its vicinity. A probe request can be sent on one or more channels in either passive or active scanning mode. In passive scanning mode, a STA listens for beacon frames from APs on each channel. In active scanning mode, a STA sends probe requests on each channel and waits for probe responses from APs. A probe request is usually sent at the minimum basic rate, which is the lowest data rate among the supported rates that is required for all STAs to join and communicate with a BSS. The minimum basic rate can vary depending on the configuration of each BSS, but it is typically one of these values: 1 Mbps, 2 Mbps, 5.5 Mbps, or 11 Mbps in the 2.4 GHz band. The other options are not correct, as they do not reflect how probe requests are usually sent in the 2.4 GHz band. MCS 0 is a modulation and coding scheme used by 802.11n/ac devices in either band, but it is not a data rate per se. 6 Mbps is a data rate used by OFDM devices in either band, but it is not usually configured as a minimum basic rate in the 2.4 GHz band. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 123-124
NEW QUESTION # 34
What is an AIFS?
- A. A form of aggregation performed at the PHY layer based on 802.lie UP values interpreted from DSCP values
- B. A variable Interframe Space introduced by 802.lie to help prioritize medium access for different Access Categories
- C. The shortest period of time a STA can sleep
- D. A medium access method introduced by 802.lln, but never implemented
Answer: B
Explanation:
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
NEW QUESTION # 35
Given: The Frame Check Sequence (FCS) is a 32 CRC used for error detection.
The CRC is calculated over what?
- A. Mac Header and Frame Body only
- B. PHY Header and Mac Header only
- C. PHY Header, MAC Header and Frame Body
- D. Frame Body only
Answer: A
Explanation:
Explanation
The CRC is calculated over the MAC Header and Frame Body only. The CRC (Cyclic Redundancy Check) is a 32-bit value that is used for error detection in wireless transmissions. The CRC is calculated over the MAC Header and Frame Body of a PSDU, which are the parts of the data unit that contain information such as source and destination addresses, frame type, frame control, sequence number, payload, etc. The CRC is appended to the end of the PSDU as a FCS (Frame Check Sequence) field. The CRC is not calculated over the PHY Header or PHY Preamble, which are parts of the PPDU that contain information such as modulation, coding, data rate, etc. The PHY Header and PHY Preamble are added or removed by the PHY layer during the conversion between PSDU and PPDU. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 4: 802.11 Physical Layer, page 97-98
NEW QUESTION # 36
The PHY layer provides framing by adding a header to create what type of data unit?
- A. MPDU
- B. PPDU
- C. PSDU
- D. MSDU
Answer: B
Explanation:
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
NEW QUESTION # 37
In which element of a Beacon frame would you look to identity the current HT protection mode in which an AP is operating?
- A. HT Capabilities Element
- B. HT Operations Element
- C. ERP Information Element
- D. HT Protection Element
Answer: B
Explanation:
Explanation
The HT protection mode in which an AP is operating can be identified by looking at the HT Operations element in a Beacon frame. The HT Operations element is a part of the Beacon frame that contains information about the High Throughput (HT) capabilities and operation of an 802.11n BSS. The HT Operations element has a field called HT Protection, which indicates how the BSS protects its HT transmissions from interference or collisions with non-HT devices or BSSs. The HT Protection field can have four values: No Protection, Nonmember Protection, 20 MHz Protection, or Non-HT Mixed Mode. The other options are not correct, as they do not contain information about the HT protection mode. The HT Protection element does not exist, the ERP Information element is used for Extended Rate PHY (ERP) protection mode for 802.11g devices, and the HT Capabilities element is used for indicating the supported HT features of an individual device. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 125-126
NEW QUESTION # 38
Why would a STA that supports 802.11k Radio Measurement send a Neighbor Request to an AP?
- A. To request a list of neighboring APs which the STA can use as roaming candidates
- B. To inform the current AP about the STA's intent to roam to a neighboring AP, ensuring a seamless handover
- C. To learn about neighboring interference sources and tune its RF radio accordingly
- D. To request a list of neighboring STAs which enables the STA to better pick the right protection mechanisms
Answer: A
Explanation:
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.
NEW QUESTION # 39
In a Spectrum Analyzer the Swept Spectrogram plot displays what information?
- A. The RF time domain
- B. Wi-Fi Device information
- C. RF power present at a particular frequency over the course of time
- D. Reductions in frame transmissions
Answer: C
Explanation:
Explanation
The Swept Spectrogram plot is a spectrum analysis plot that shows the RF power present at a particular frequency over the course of time. It can help identify trends and patterns in the RF spectrum over a longer period of time. It can also show how the RF environment changes over time and how different sources of RF signals affect each other. The other options are not correct, as they describe different types of plots or information that are not related to the Swept Spectrogram plot. References: [Wireless Analysis Professional Study Guide], Chapter 3: Spectrum Analysis, page 72-73
NEW QUESTION # 40
You are troubleshooting a client that is experiencing slow WLAN performance. As part of the troubleshooting activity, you start a packet capture on your laptop close to the client device. While analyzing the packets, you suspect that you have not captured all packets transmitted by the client. By analyzing the trace file, how can you confirm if you have missing packets?
- A. The missing packets will be shown as CRC errored packets
- B. Retransmission are an indication of missing packets
- C. Look for gaps in the sequence number in MAC headers.
- D. Protocol Analyzers show the number of missing packets in their statistics view
Answer: C
Explanation:
Explanation
One way to confirm if you have missing packets in your packet capture is to look for gaps in the sequence number in MAC headers. The sequence number is a 12-bit field in the MAC header that is used to identify and order data frames within a traffic stream. The sequence number is incremented by one for each new data frame transmitted by a STA, except for retransmissions, fragments, and control frames. The sequence number can range from 0 to 4095, and then wraps around to 0. If you see a jump or a gap in the sequence number between two consecutive data frames from the same STA, it means that you have missed some packets in between. The other options are not correct, as they do not confirm if you have missing packets in your packet capture. CRC errored packets are packets that have been corrupted during transmission and have failed the error detection check. Protocol analyzers may show the number of CRC errored packets in their statistics view, but not the number of missing packets. Retransmissions are an indication of packet loss or collision, but not necessarily of missing packets in your capture. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 114-115
NEW QUESTION # 41
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. Place one of the London APs into spectrum analyzer mode and monitor the situation over lunch time
- 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. 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
Answer: A
Explanation:
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
NEW QUESTION # 42
How does a VoIP Phone, using WMM Power Save, request data frames buffered at the AP?
- A. The VoIP phone transmits a WMM Action frame
- B. The VoIP phone sets the More Data bit in the MAC Header to 1
- C. The VoIP phone transmits a trigger frame, which is a QoS Null frame or a QoS Data frame
- D. The VoIP phone transmits a PS-Poll frame
Answer: C
Explanation:
Explanation
A VoIP phone, using WMM Power Save, requests data frames buffered at the AP by transmitting a trigger frame, which is a QoS Null frame or a QoS Data frame. WMM Power Save is a power saving mode that allows a STA (station) to conserve battery power by periodically sleeping and waking up. WMM Power Save is based on WMM (Wi-Fi Multimedia), which is a QoS (Quality of Service) enhancement that provides prioritized and differentiated access to the medium fordifferent types of traffic. 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 trigger frame to the AP, indicating its AC (Access Category), which is a logical queue that corresponds to its QoS level. A trigger frame can be either a QoS Null frame or a QoS Data frame, depending on whether it has any payload or not. The AP then responds with one or more data frames from the same AC as the trigger frame, followed by an ACK or BA (Block Acknowledgement) frame from the STA. The other options are not correct, as they are not used by a VoIP phone using WMM Power Save to request data frames buffered at the AP. A PS-Poll (Power Save Poll) frame is used by a STA using legacy power save mode, not WMM Power Save mode, to request data frames buffered at the AP. A PS-Poll frame does not indicate any AC or QoS information. Setting the More Data bit in the MAC header to 1 does not request any data frames from the AP, but indicates that there are more data frames to be sent by the STA or received by the STA.
Transmitting a WMM Action frame does not request any data frames from the AP, but performs various management actions related to WMM features, such as admission control, parameter update, etc. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 7: QoS Analysis, page
198-199
NEW QUESTION # 43
Where would you look in a packet trace file to identify the configured Minimum Basic Rate (MBR) of a BSS?
- A. Supported Rates & Extended Supported Rates elements in a Beacon frame
- B. In the MBR Action frame
- C. In the Minimum Basic Rate Element in a Beacon frame
- D. In the MBR Information Element in an Association Response frame
Answer: A
Explanation:
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
NEW QUESTION # 44
Finish the statement:
It is possible to distinguish between_______22 MHz transmissions and________20 MHz transmissions when looking at an FFT plot.
- A. HR/DSSS and ERP
- B. ERP and VHT
- C. HT and VHT
- D. OFDM and HT
Answer: D
Explanation:
Explanation
It is possible to distinguish between OFDM 20 MHz transmissions and HT 20 MHz transmissions when looking at an FFT plot. OFDM and HT are two different modulation schemes used by 802.11 WLANs. OFDM is used by legacy 802.11a/g devices, while HT is used by newer 802.11n/ac devices. OFDM and HT have different spectral characteristics that can be observed on an FFT plot. OFDM transmissions have a flat spectrum with sharp edges, while HT transmissions have a tapered spectrum with rounded edges. This is because HT uses guard intervals and cyclic prefixes to reduce inter-symbol interference and improve performance. The other options are not correct, as they do not describe different modulation schemes or channel widths that can be distinguished on an FFT plot. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 3: Spectrum Analysis, page 70-71
NEW QUESTION # 45
Which one of the following should be the first step when troubleshooting a WLAN issue?
- A. Identify probable causes
- B. Perform an initial WLAN scan and see if any obvious issues stand out
- C. Identify capture locations
- D. Define the problem
Answer: D
Explanation:
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
NEW QUESTION # 46
When performing protocol analysis, you capture an 802.1 lac data frame on channel 52, transmitted at MCS 8.
At what data rate was the PHY Preamble transmitted?
- A. 78 Mbps
- B. 86.7 Mbps
- C. 54 Mbps
- D. 6 Mbps
Answer: D
Explanation:
Explanation
The data rate at which the PHY preamble was transmitted is 6 Mbps. 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 detect and synchronize with the signal. The PHY preamble is always transmitted at a fixed data rate that depends on the type of PPDU (e.g., OFDM, HT, VHT, HE). For an 802.1 lac data frame on channel 52, which uses VHT PPDUs, the data rate for the PHY preamble is 6 Mbps. This data rate does not depend on MCS (Modulation and Coding Scheme), which only affects the data rate for the PSDU. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 4: 802.11 Physical Layer, page 99-100
NEW QUESTION # 47
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CWNP CWAP-404 Exam Topics:
| Section | Objectives |
|---|---|
Protocol Analysis - 15% | |
| Capture 802.11 frames using the appropriate methods | - Select capture devices
- Install monitor mode drivers |
| Understand and apply the common capture configuration parameters available in protocol analysis tools | - Save to disk - Packet slicing - Event triggers - Buffer options - Channels and channel widths - Capture filters - Channel scanning and dwell time |
| Analyze 802.11 frame captures to discover problems and find solutions | - Use appropriate display filters to view relevant frames and packets - Use colorization to highlight important frames and packets - Configure and display columns for analysis purposes - View frame and packet decodes while understanding the information shown and applying it to the analysis process - Use multiple adapters and channel aggregation to view captures from multiple channels - Implement protocol analyzer decryption procedures - View and use a capture’s statistical information for analysis - Use expert mode for analysis - View and understand peer maps as they relate to communications analysis |
| Utilize additional tools that capture 802.11 frames for analysis and troubleshooting | - WLAN scanners and discovery tools - Protocol capture visualization and analysis tools - Centralized monitoring, alerting, and forensic tools |
| Ensure appropriate troubleshooting methods are used with all analysis types | - Define the problem - Determine the scale of the problem - Identify probable causes - Capture and analyze the data - Observe the problem - Choose appropriate remediation steps - Document the problem and resolution |
Spectrum Analysis - 10% | |
| Capture RF spectrum data and understand the common views available in spectrum analyzers | - Install, configure, and use spectrum analysis software and hardware - Capture RF spectrum data using handheld, laptop-based, and infrastructure spectrum capture solutions - Understand and use spectrum analyzer views
|
| Analyze spectrum captures to identify relevant RF information and issues | - RF noise floor in an environment - Signal-to-Noise Ratio (SNR) for a given signal - Sources of RF interference and their locations - RF channel utilization - Non-Wi-Fi transmitters and their impact on WLAN communications - Overlapping and non-overlapping adjacent channel interference - Poor performing or faulty radios |
| Analyze spectrum captures to identify various device signatures | - Identify various 802.11 PHYs
- Identify non-802.11 devices based on RF behaviors and signatures
|
| Use centralized spectrum analysis solutions | - AP-based spectrum analysis - Sensor-based spectrum analysis |
PHY Layers and Technologies - 10% | |
| Understand and describe the functions of the PHY layer and the PHY protocol data units (PPDUs) | - DSSS (Direct Sequence Spread Spectrum) - HR/DSSS (High Rate/Direct Sequence Spread Spectrum) - OFDM (Orthogonal Frequency Division Multiplexing) - ERP (Extended Rate PHY) - HT (High Throughput) - VHT (Very High Throughput) - HE (High Efficiency)
|
| Apply the understanding of PHY technologies, including PHY headers, preambles, training fields, frame aggregation, and data rates, to captured data | |
| Identify and use PHY information provided within pseudo-headers in protocol analyzers | - Pseudo-Header formats
- Key pseudo-header content
|
| Recognize the limits of protocol analyzers to capture PHY information including NULL data packets and PHY headers | |
| Use appropriate capture devices based on proper understanding of PHY types | - Supported PHYs - Supported spatial streams |
MAC Sublayer and Functions - 25% | |
| Understand frame encapsulation and frame aggregation | - Frame aggregation (A-MSDU and A-MPDU) |
| Identify and use MAC information in captured data for analysis | - Management, Control, and Data frames - MAC frame formats and contents
- 802.11 Management frame formats
- Data and QoS Data frame formats
|
| Validate BSS configuration through protocol analysis | - Country code - Minimum basic rate - Supported rates and coding schemes - Beacon interval - WMM settings - RSN settings - HT/VHT/HE operations - Channel width - Primary channel - Hidden or non-broadcast SSIDs |
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