CWNP CWAP-404 Certified Wireless Analysis Professional Exam Practice Test

The difference between a Data frame and a QoS-Data frame is that QoS Data frames include a QoS control field. A Data frame is a type of data frame that is used to carry user data or upper layer protocol data between STAs and APs. A QoS Data frame is a type of data frame that is used to carry user data or upper layer protocol data between STAs and APs that support QoS (Quality of Service) features. QoS features allow different types of traffic to be prioritized and handled differently according to their QoS requirements, such as delay, jitter, throughput, etc. QoS Data frames include a QoS control field in their MAC header, which contains information such as traffic identifier (TID), queue size (TXOP), acknowledgment policy (ACK), etc., that are used for QoS purposes. The other options are not correct, as they do not describe the difference between Data and QoS Data frames. QoS Data frames do not include a DSCP (Differentiated Services Code Point) control field, which is part of the IP header in the network layer, not the MAC header in the data link layer. QoS Data frames do not include a QoS information element (IE), which is part of some management frames that indicate QoS capabilities or parameters, not data frames. QoS Data frames do not include an 802.1Q VLAN tag, which is part of some Ethernet frames that indicate VLAN membership or priority, not wireless frames. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 118-119

A Reassociation Request frame is sent every time a STA roams from one AP to another within the same ESS. A Reassociation Request frame is similar to an Association Request frame, but it also contains the BSSID of the current AP that the STA is leaving. This allows the new AP to coordinate with the old AP and transfer the STA’s context information, such as security keys, QoS parameters, and buffered frames. This way, the STA can maintain its connectivity and session continuity during roaming . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 195;CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 196.

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

RTS is not a valid acknowledgement frame. RTS stands for Request To Send, and it is a control frame that is used to initiate an RTS/CTS exchange before sending a data frame. The purpose of an RTS/CTS exchange is to reserve the medium for a data transmission and avoid collisions with hidden nodes. An acknowledgement frame is a control frame that is used to confirm the successful reception of a data frame or a block of data frames. The valid acknowledgement frames are CTS (Clear To Send), Ack (Acknowledgement), and Block Ack (Block Acknowledgement) . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 186; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 187; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 189; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 190.

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.

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

An 802.11 wireless adaptor is required for Wi-Fi integration in laptop-based spectrum analyzer software in addition to the spectrum analysis adapter. The spectrum analysis adapter is a hardware device that captures the RF signals in the wireless environment and sends them to the spectrum analyzer software for analysis and display. The 802.11 wireless adapter is a hardware device that connects the laptop to the wireless network and allows the spectrum analyzer software to correlate the RF data with the Wi-Fi data, such as SSID, channel, and BSSID. This enables the spectrum analyzer software to provide more context and insight into the spectrum activity and its impact on the Wi-Fi network. A firmware upgrade for the spectrum analysis adapter is not required for Wi-Fi integration, but it may be needed to fix bugs or add features to the device. A directional antenna is an antenna that focuses the RF energy in a specific direction and has a high gain and a narrow beamwidth. A directional antenna can be used with a spectrum analysis adapter to pinpoint the location or source of interference or noise in the wireless environment, but it is not required for Wi-Fi integration. SNMP read credentials to the WLAN controller or APs are not required for Wi-Fi integration, but they may be useful for obtaining additional information about the wireless network configuration and performance from the network devices.References:

• CWAP-404 Study Guide, Chapter 4: Spectrum Analysis and Troubleshooting, page 123
• CWAP-404 Objectives, Section 4.2: Integrate Wi-Fi data with spectrum analysis data
• CWAP-404 Study Guide, Chapter 4: Spectrum Analysis and Troubleshooting, page 131

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

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

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

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

A hexadecimal value is a value that uses base 16 notation, which means it can have digits from 0 to 9 and letters from A to F. A hexadecimal value is usually preceded by 0x to indicate that it is hexadecimal and not decimal or binary. For example, 0x0A is hexadecimal for 10 in decimal or 00001010 in binary. The other options are not valid prefixes for hexadecimal values.References:

• CWAP-404 Study Guide, Chapter 2: Protocol Analysis, page 35
• CWAP-404 Objectives, Section 2.2: Analyze field values

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

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.

 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.

The To DS and From DS flags should be set to 0 in an Association Response frame. An Association Response frame is a type of management frame that is transmitted by an AP to accept or reject an association request from a STA. The To DS (To Distribution System) and From DS (From Distribution System) flags are two bits in the Frame Control field of the MAC header that indicate whether a frame is destined for or originated from the DS (Distribution System), which is a system that connects multiple BSSs together. The To DS and From DS flags can have four possible combinations: 00, 01, 10, or 11. For an Association Response frame, which is sent from an AP to a STA within a BSS, both flags should be set to 0. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 5: 802.11 MAC Sublayer, page 121-122

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

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