PW0-270 Online Practice Questions and Answers

What is the purpose of a PHY preamble?

A. It provides the receiver(s) with an opportunity for RF channel synchronization prior to the start of the PLCP header.

B. It communicates important information about the PSDU's length, rate, and upper layer protocol- related parameters.

C. It provides a cyclic redundancy check (CRC) for the receiving station to validate that the PLCP header was received correctly.

D. It indicates to the PHY the modulation that shall be used for transmission (and reception) of the PSDU.

According to 802.11-2007, in what frame type(s) might you find the PMK Count and PMKID List fields?

A. All frames that include the RSN IE

B. Only (Re)Association Request frames

C. Beacon and Probe Response frames

D. EAPoL 4-Way Handshake frames

E. Authentication and Association Request and Response frames

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.

In which 802.11 frames is the SSID present, provided the SSID is not removed through proprietary software configuration by an administrator? (Choose 3)

A. Association Request

B. Reassociation Request

C. Probe Response

D. Disassociation

E. Authentication

F. Association Response

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

The IEEE 802.11 Dynamic Frequency Selection (DFS) service is capable of performing what functions? (Choose 2)

A. Establishing an interference baseline on all 2.4 GHz channels

B. Using modulation switching techniques to avoid interfering with radar systems

C. Testing channels for radar before using a channel and while operating in a channel

D. Suspending operations on a channel with high IEEE 802.11 co-channel interference

E. Requesting and reporting of measurements in the current and other channels

An HT STA does not receive an ACK for a first-attempt data frame that it transmitted. Assuming this STA is not using BlockAcks in this case, what happens to the HT STA's EDCA contention window?

A. The slot time within the contention window decreases by 50%.

B. It varies because the backoff algorithm is random.

C. The contention window approximately doubles in size.

D. The contention window is not affected by failed Data frame delivery.

E. The contention window is immediately closed, and the frame is retransmitted.

What two IEEE 802.11 entities may be used to separate successful transmissions within an EDCA TXOP? (Choose 2)

A. SIFS

B. AIFS

C. ACK

D. CAP

E. PIFS

F. EIFS

G. RIFS

What must occur before an HT STA operating in an EDCA BSS can transmit a data frame over the wireless medium? (Choose 3) A. Its NAV must be equal to one.

B. The STA must receive a BlockAck, resetting the NAV to zero.

C. The appropriate interframe space must expire.

D. The backoff timer for the AC must equal zero.

E. Its CCA must report that the medium is idle.

F. The AP must issue the STA a TXOP.

Which statement accurately describes IEEE 802.11 Power Save operation in a Basic Service Set that does not support the QoS facility?

A. Following a period of time in a low power state, client stations wake themselves and automatically poll the access point for traffic using a PS-Poll frame.

B. When the access point's buffer is full, the access point wakes all client stations using a PS-Poll frame so that they can receive the data.

C. Upon receiving traffic for a dozing station, the access point wakes the client station using a PS-Poll frame so that the client station can receive the data.

D. After waking from a low power state, client stations listen for the next Beacon to determine if sending a PS-Poll frame to the access point is necessary.

E. After waking at a scheduled TBTT, client stations send Null Function frames to the access point with the Power Management bit set back to zero.

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.

Your wireless network troubleshooting kit includes an antenna with the following specifications:

Gain: 5 dBi Azimuth Beamwidth: 55 degrees Elevation Beamwidth: 50 degrees Frequency Range: 2.4 - 2.5 GHz and 4.9 - 5.9 GHz Polarization: Linear Impedance: 50 Ohms

For what aspect of network troubleshooting would this antenna be most useful?

A. Capturing BSS-wide CRC error and retry statistics in most indoor WLAN environments

B. Identifying problems with Fresnel zone clearance in long range (10+ miles / 16+ km) point-to-point links

C. Finding the physical location of an interfering transmitter to identify and remove the source

D. Increasing resolution bandwidth (RBW) on a spectrum analyzer to improve signature identification features

E. Matching transmit and receive capabilities for most client stations to reproduce client reception issues

Given: The graphic is taken from a spectrum analyzer.

What types of RF transmitters are illustrated?

A. An IEEE 802.11 HR/DSSS security camera on channel 6 and an RFID tag

B. A Bluetooth headset and a narrowband RF jamming device

C. A 2.4 GHz cordless phone and an OpenAir FHSS system

D. A 20 MHz HT IEEE 802.11 system using channel 1 and a microwave oven

Using the exhibit as a reference,

which spectrum plots display, in real time, the value of RF amplitude as a function of radio frequency?

A. 1 and 2

B. 1 and 3

C. All of the plots

D. 1, 3, and 4

E. 3 and 4

Shown is a screenshot of a wireless protocol analyzer displaying the decode information for a single 802.11 encrypted data + CF-Poll frame. The infrastructure BSS on which this information was captured is using WEP and this particular frame was sent from a client station (STA) to an access point (AP).

As a protocol analyst, how would you explain the existence of this frame on the wireless medium given the information in the decode?

A. The IEEE 802.11 network is using both version 1 and version 2 protocols simultaneously. This unexpected frame is from the version 2 protocol set.

B. The frame was sent by a client station that does not comply with IEEE HR/DSSS standard to an access point that is Wi-Fi certified.

C. The access point is operating as a repeater, and clients must poll repeater access points in order to transmit data frames through them.

D. The frame was misinterpreted because of insufficient information received by the analyzer due to frame corruption.