PW0-270 Online Practice Questions and Answers

Which statement is true regarding the Association Identifier (AID) used in IEEE 802.11 WLANs?

A. The AID has a maximum value of 2048, and is used to uniquely identify a wireless client station associated with an access point.

B. The AID has a maximum value of 2007, and resides in the duration/ID field of a PS-Poll frame.

C. The client station is assigned an AID value in the 802.11 authentication response frame.

D. The AID field is present only in Beacons frames.

E. The AID is used by the access point in EDCA mode to reduce duplicate transmissions when sending multicasts.

The Retry subfield is found in which IEEE 802.11 frame field?

A. Sequence Control field

B. Protocol Order field

C. Data Control field

D. Frame Control field

E. MAC Service Data Unit field

F. QoS Control field

Which statements accurately describe IEEE 802.11 EDCA collision handling in a WMM-compliant infrastructure WLAN? (Choose 2)

A. When frames collide within a QoS STA, data frames from lower priority ACs behave (as it relates to contention) as if there were an external collision on the wireless medium.

B. Collisions between contending EDCAFs within a QoS STA are resolved within the QoS STA

C. When a frame transmission on the wireless medium fails, the transmitter may not transmit another frame from any AC or to any destination until the frame experiencing a failure is successfully transmitted or the max retry count for that frame is reached.

D. The WMM specification requires use of RTS/CTS as part of the EDCAF within each QoS STA to avoid internal collisions between ACs.

E. After frames collide within a QoS STA and the lower priority AC subsequently gains a TXOP, the retry bit in the MAC header must be set to 1 to indicate a retry.

IEEE 802.11-2007 specifies two ERP protection mechanisms: RTS/CTS and CTS-to-Self. Which statement is true regarding these two protection mechanisms? (Choose 2)

A. RTS and CTS frames use Short Interframe Spaces (SIFS), and CTS-to-Self frames use PCF Interframe Spaces (PIFS).

B. Use of RTS/CTS requires more overhead than CTS-to-Self due to a higher number of frames transmitted onto the wireless medium.

C. RTS and CTS frames are relayed through the access point, whereas the CTS-to-Self frames are not.

D. A CTS-to-Self frame sent by a client station may reach fewer nodes than the RTS/CTS frame exchange.

E. By definition, all associated client stations in a BSS can hear RTS, CTS, and CTS-to-Self frames, so RTS/CTS and CTS-to-Self mechanisms have equal effectiveness.

F. Aside from the Subtype subfield of the Frame Control field, the generic MAC header format of RTS and CTS frames are identical.

As it pertains to HT L-SIG TXOP Protection, what statement is true?

A. Support for L-SIG TXOP Protection is indicated by HT stations in the L-SIG field of the PLCP header of HT-mixed format frames.

B. Support for L-SIG TXOP Protection is indicated in the HT Capabilities Info field of (re)association request frames sent by ERP, OFDM, and HT-OFDM stations.

C. An L-SIG TXOP protected frame exchange sequence always begins with an RTS/CTS or a CTS-to- Self.

D. L-SIG TXOP Protection is specified for the purpose of protecting OFDM (802.11a/g) and HT- OFDM (802.11n) transmissions from HR/DSSS stations.

Given: The exhibit shows a small network environment with dual-band APs.

What is true of the network shown in this spectrum analyzer trace?

A. There are at least three APs operating in this environment. They are operating on channels 149, 153, and 161.

B. There are two 40 MHz BSSs in this environment. One AP has some 40 MHz traffic while the other AP has no client traffic.

C. Only one AP in this network is configured to use the upper UNII band (UNII-3). All other APs are in lower 5 GHz channels.

D. Two 802.11a APs are near the spectrum analyzer and are heavily utilized on channels 149 and 153.

Given: Before installing a Wi-Fi network, ABC Company performed a spectrum analysis looking for problems. The 2.4 GHz RF spectrum looked like Image-A. After installing an ERP WLAN, ABC Company performed another spectrum analysis during business hours. The 2.4 GHz RF spectrum then looked like Image-B close to an AP on channel 1.

Now the 2.4 GHz RF spectrum looks like Image-C and access points and clients can no longer communicate on channel 1. What is happening on channel 1?

A. The access point's antenna connectors have been tampered with, causing "spike and shear" RF transmissions that are not compatible with the OFDM PHY format. For that reason, client devices cannot receive the AP's transmissions without error.

B. A high-power, narrowband RF interference source on channel 1 is causing the CCA energydetects(ED) function on 802.11 devices to indicate a busy medium because the signal source is above the ED threshold.

C. Stronger transmissions from licensed 2.4 GHz users, such as HAM operators, are compressing the transmissions from the channel 1 access points into the lower portion of the band.

D. The shape of the signals in images B and C indicates that a licensed user in this frequency range has enabled the "guard bands" in an effort to restrict local interference with other systems.

E. Detection of a DFS radar event has discontinued 802.11 operation on channel 1, but the access point's Channel Switch Announcement frame cannot be sent due to the presence of radar.

As it relates to a spectrum analyzer, complete the following sentence.

The ____________ plot always displays the percentage of time (shown on the Y axis) that the overall RF power is a certain specified threshold (of amplitude) above the noise floor for a given frequency range (shown on the X axis).

A. Real-Time FFT

B. Swept Spectrogram

C. FFT Duty Cycle

D. Interferer Count

E. SNR

When 802.11 standard compliant AES-CCMP security is being used with IPSec/ESP for layered security, what will a WLAN protocol analyzer see as the security mechanism in use when a user browses to an HTTPS secured web page?

A. AES-CCMP

B. IPSec/ESP

C. SSLv3

D. AES-CCMP and IPSec/ESP

E. AES-CCMP, IPSec/ESP, AND SSLv3

Why is a high CRC error rate in L2 protocol analysis software NOT always a valid indicator of network performance? (Choose 3)

A. If protocol analysis software is not properly configured with frame decryption parameters, it can't accurately calculate a CRC, which includes the encrypted frame body contents.

B. If the protocol analysis radio hardware is not located in the same area as intended client devices or APs, its data sampling may not be representative of actual traffic on the network.

C. Radio and antenna hardware used for protocol analysis may not match the receive sensitivity, diversity, MIMO, or antenna gain capabilities of the network WLAN hardware.

D. Layer 2 protocol analysis can only collect and interpret data that is received properly at the MAC layer, and cannot quantify some PHY-layer problems.