Wireless LAN Analysis
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What statement in relation to the 802.11g access point
responsibilities in the Basic Service Set is true
when working in an 802.11b/g mixed mode environment
where both 802.11b and 802.11g client stations are
present and transmitting data on the network?
A. The access point may transmit beacons using a short
preamble only if all of the client stations in the
BSS have indicated support for short preambles.
B. If beacons are transmitted using short preambles,
all associated client stations are required to transmit
all data frames using short preambles.
C. The access must transmit beacons using a short
preamble in a mixed mode environment. Client stations
not supporting short preambles will not be able to
D. The access point will alternate transmitting beacons
using long and short preambles so that client stations
using either preamble length can associate.
Which are the two most important mechanisms employed
by an 802.11 BSS to cause stations that are not the
Point Coordinator to defer during a contention-free
period? (Choose two)
A. CF Parameter Set elements in the Beacons
B. Point Coordination Function Interframe Space (PIFS)
C. Contention-Free Polling List broadcasts
D. Null Function data frames using SIFS
E. All frames transmitted during the CFP have a Duration
field value of 32,768
F. The Pseudorandom Backoff Timer in each station
Which is an accurate description of IEEE 802.11 compliant
Power Save mode operation, in a DCF Basic Service
A. 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.
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. 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
D. After waking at a schedule TBTT, client stations
automatically send Null Function frames to the access
point with the Power Management bit cleared.
E. 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.
The 802.11b standard can judge an 802.11b PPDU's preamble
that consists of two fields to be "long"
or "short" collectively. Which two statements
concerning the PLCP preamble are true? (Choose two)
A. A long preamble uses a Sync field of 128 bits,
and both stations and access points may have configurable
B. An 802.11b access point that supports both long
and short preambles may allow stations that are using
different preamble lengths to communicate through
C. When short preambles are being used, the Sync and
SFD fields both consist of 16 bits. Only access points
have configurable preamble lengths.
D. A short preamble uses a Sync field of 40 bits,
and stations and access points must have matching
preamble lengths in order to communicate.
E. 802.11g stations associating to 802.11b access
points must use the DSSS preamble length specified
by the access point.
F. Long and short preamble lengths are both variable
depending on the modulation in use on the network,
and access points always inform stations of the preamble
length in use on the network.
Which of the following is a structural difference
between a MAC Protocol Data Unit (MPDU) and a MAC
Management Protocol Data Unit (MMPDU), according to
the IEEE 802.11 standard?
A. 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.
B. The MPDU frame FCS field is 4 bytes, while the
MMPDU frame FCS field is 8 bytes.
C. The MMPDU frame body is limited to 200 bytes, whereas
the MPDU frame body can carry up to 2312 bytes.
D. An MMPDU header may only contain three address
fields, but an MPDU may have four address fields.
Which are two fixed fields in an 802.11 Authentication
frame? (Choose two)
A. Contention-free parameter set
B. Supported rates
C. Transaction sequence number
D. Algorithm number
E. Challenge text