CWAP PW0-270 問題集

質問 1：
While at a government-operated facility, you are attempting to troubleshoot a WLAN performance problem using a wireless protocol analyzer. When you start capturing frames, you see a proprietary layer 2 protocol running over the ERP network as shown in this screenshot. The facility's WLAN administrator confirms that this protocol is proprietary and used for both data encryption and compression.

How will this information affect the steps you take to troubleshoot performance problems on this WLAN?
A. In order to troubleshoot performance problems on a network using proprietary encryption protocols like this one, you must use a wireless protocol analyzer that has integrated support for the protocol in use.
B. The proprietary encryption protocol will have no effect on your troubleshooting steps because the wireless protocol analyzer can still decode the PLCP and MAC headers of Data frames. This situation is essentially no different than troubleshooting a WLAN that uses WPA2-Personal.
C. As long as you load the proprietary software codec onto your analyzer computer, you will be able to see all of the Data frame information fully decoded. Loading the proprietary software codec will allow you to troubleshoot the WLAN as though no encryption were in use.
D. Troubleshooting will be somewhat limited because only part of the information needed for performance measurements by the analyzer is encrypted. Each Data frame's MAC header will be encrypted, but the PLCP header can still be decoded successfully.
正解：B

質問 2：
What is the purpose of a PHY preamble?
A. It indicates to the PHY the modulation that shall be used for transmission (and reception) of the PSDU.
B. It provides a cyclic redundancy check (CRC) for the receiving station to validate that the PLCP header was received correctly.
C. It communicates important information about the PSDU's length, rate, and upper layer protocol-related parameters.
D. It provides the receiver(s) with an opportunity for RF channel synchronization prior to the start of the PLCP header.
正解：D

質問 3：
Which statements regarding an IEEE 802.11 Channel Switch Announcement frame are true? (Choose 2)
A. Channel Switch Announcement frames use the Action frame body format.
B. Channel Switch Announcement frames are the only place where the Channel Switch Announcement element is found.
C. In an infrastructure BSS, Channel Switch Announcement frames may be transmitted by either the AP or an associated STA.
D. Channel Switch Announcement elements may be carried in Beacon management frames.
E. Channel Switch Announcement frames are transmitted and retransmitted on a channel until all associated STAs successfully move to the new channel.
正解：A,D

質問 4：
According to the IEEE 802.11 standard, what is one structural difference between a MAC Protocol Data Unit (MPDU) and a MAC Management Protocol Data Unit (MMPDU)?
A. The MPDU frame's FCS field is 4 bytes, while the MMPDU frame's FCS field is 8 bytes.
B. The MMPDU frame body is limited to 300 bytes, whereas the MPDU frame body can carry up to 2304 bytes.
C. Both the MPDU and MMPDU have a QoS Control (QC) field, but all bits of the MMPDU's QC field are always 0.
D. An MMPDU header may only contain three address fields, but an MPDU may have four address fields.
E. The MPDU header always places the BSSID in the first address field, but in the MMPDU the BSSID can be found in any of the address fields.
正解：D

質問 5：
What MAC layer information will a dual-band 802.11n protocol analyzer capture if it is capturing data frames encrypted with WPA2-Enterprise? (Choose 2)
A. Source IP Address
B. Null Data frames
C. Short Interframe Spaces
D. TCP SYN datagram
E. Legacy Signal field
F. Sequence Control fields
正解：B,F

質問 6：
What IEEE 802.11 technology is illustrated by the exhibit?

A. Jumbo frames
B. A-MPDU
C. Fragmentation
D. A-MSDU
E. TCP Fragment Bursting
F. U-APSD
正解：D