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

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.

In a protocol analyzer, you would find an indication that a frame was transmitted as part of an A-MPDU by looking at the Aggregation flag in the Radio Tap Header. The Radio Tap Header is a pseudo-header that is added by some wireless capture devices to provide additional information about the physical layer characteristics of a frame. The Aggregation flag is one of the fields in this header, and it indicates whether the frame belongs to an A-MPDU or not. If the flag is set to 1, it means that the frame is part of an A-MPDU; if it is set to 0, it means that the frame is not part of an A-MPDU . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 9: PHY Layer Frame Formats and Technologies, page 303; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 9: PHY Layer Frame Formats and Technologies, page 304.

The function of the PHY layer is to convert PSDUs to PPDUs for transmissions and PPDUs to PSDUs for receptions. A PSDU (PHY Service Data Unit) is the data unit that is passed from the MAC layer to the PHY layer for transmission, or from the PHY layer to the MAC layer for reception. 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 and a PHY header, which contains information such as modulation, coding, and data rate. The PHY layer adds or removes the PHY header to or from the PSDU during the conversion process.  References:  [Wireless Analysis Professional Study Guide CWAP-404], Chapter 4: 802.11 Physical Layer, page 97-98

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 below 1 2 . References: CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 13: Troubleshooting Common Wi-Fi Issues, page 496 1 ; CWAP-404 Certified Wireless Analysis Professional Study and Reference Guide, Chapter 14: Troubleshooting Tools, page 527 2 .

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 strength are 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

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