CWAP-404 Certified Wireless Analysis Professional Question and Answers

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

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

Every Beacon frame must contain a DTIM is not a true statement concerning DTIMs. DTIM stands for Delivery Traffic Indication Message, and it is a subfield within the TIM (Traffic Indication Map) element in a Beacon frame. The DTIM indicates how many Beacon frames (including the current one) will appear before the next DTIM. For example, if the DTIM interval is set to 3, it means that every third Beacon frame will contain a DTIM. Buffered broadcast and multicast traffic will be transmitted following a DTIM, so that STAs in power save mode can wake up and receive them. The DTIM interval can also dictate when an STA will wake up to listen to Beacon frames, as some STAs may choose to only listen to Beacon frames that contain a DTIM . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 200; CWAP-404 CertifiedWireless Analysis Professional Study and Reference Guide, Chapter 6: MAC Sublayer Frame Exchanges, page 201.

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 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

The Group Key Handshake consists of two frames excluding any Ack frames that may be required. The Group Key Handshake is used to distribute and update the Group Temporal Key (GTK) for encrypting broadcast and multicast traffic. The AP initiates the Group Key Handshake by sending a Group Key Message 1 frame to a STA, which contains the new GTK and other information. The STA responds with a Group Key Message 2 frame to the AP, which confirms the receipt of the GTK and other information. After this, both the AP and the STA can use the new GTK for encryption and decryption of broadcast and multicast traffic . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 7: 802.11 Security, page 246; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 7: 802.11 Security, page 247.

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

A PHY header is added to the PSDU at the PHY layer. A PHY header is a part of the PPDU that contains information such as modulation, coding, and data rate. The PHY header is added by the PHY layer when it converts a PSDU to a PPDU for transmission, or removed by the PHY layer when it converts a PPDU to a PSDU for reception. The other layers do not add or remove a PHY header. References: [Wireless Analysis Professional Study Guide CWAP-404], Chapter 4: 802.11 Physical Layer, page 97-98

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

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

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

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

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

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

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