Chapter 8

Question 1

Which mechanism listens to the wireless medium to check if another station is currently transmitting? This process is called a clear channel assesment.

Answer 1

Physical Carrier Sense

Question 2

Which type of IFS is used in between data frames during a TXOP?

Answer 2

SIFS

Question 3

This IEEE standard describes the wireless QoS standard used in current QoS compliant 802.11 devices.

Answer 3

802.11e

Question 4

What information that comes from the wired side network is used to assign traffic into 802.11e access categories on a WLAN controller?

Answer 4

802.1D priority tags

Question 5

Which field in the MAC header of an 802.11 frame resets the NAV timer for all listening 802.11 stations?

Answer 5

Duration / ID

Question 6

What is the main reason that stations need a virtual carrier sense in addition to the physical carrier sense?

Answer 6

Hidden Nodes

Question 7

802.11 uses which method for media access

Answer 7

CSMA/CA

Question 8

The carrier sense portion of CSMA/CA is performed by using which of the following methods? (Choose Two)

Answer 8

Physical Carrier Sense

Virtual Carrier Sense

Question 9

The timer used by Virtual Carrier-Sense is called what?

Answer 9

Network Allocation Vector

Question 10

This timer used by CSMA/CA ensures that control frames will have faster access to the medium then data frames.

Answer 10

Interframe Spacing

Question 11

This random back-off time period occurs after the interframe spacing timer expires.

Answer 11

Contention Window

Question 12

Which of these is the process which uses carrier sense and a series of timers to perform collision avoidance in current 802.11 equipment?

Answer 12

DCF

Question 13

HCF defines what allotted period of time in which a station can transmit multiple frames known as a frame burst?

Answer 13

TXOP

Question 14

In an 802.11 wireless transmission, collision detection is handled using which technology?

Answer 14

Positive collision detection cannot be determined

Question 15

In 802.11, ACKs are required for which of the following frames?

Answer 15

Unicast

Question 16

Wireless QoS categorizes traffic based on the priority tags assigned from the Ethernet segment. These categories include: (Choose FOUR)

Answer 16

WMM Background
WMM Video
WMM Best Effort
WMM Voice

Question 17

Control Frames such as ACK frames use this type of interframe spacing.

Answer 17

SIFS

Question 18

Two stations are waiting to transmit ACK frames and their NAV and SIFS timers both expired at the same time. What mechanism will prevent these stations from transmitting at the same time?

Answer 18

Random Backoff Timer

Question 19

Two stations are contending for the wireless media. Station A is trying to send an ACK frame and Station B is trying to send a Data Frame. Which station will transmit first?

Answer 19

Station A because the ACK frame uses SIFS and the data frame uses DIFS

Question 20

What CSMA/CA mechanism is used for medium contention? (Choose Two)

Answer 20

Contention Window

Random back-off timer

Question 21

Which of the following terms are affiliated with the virtual carrier sense mechanism? (Choose Two)

Answer 21

Network Allocation Vector

Duration / ID Field

Question 22

In regards to IEEE 802.11, DCF is also known as what?

Answer 22

Distributed Coordination Function

Question 23

Frames transmitted during a TXOP are acknowledged using?

Answer 23

Block Acknowledgements

Question 24

This is the Wi-Fi alliance certification that a wireless device is wireless QoS compatible.

Answer 24

WMM

Question 25

Normal data frames use this type of interframe spacing.

Answer 25

DIFS