CWS CWS MAC Layer Functions 2

Question 1

What is the primary purpose of the Distributed Coordination Function (DCF) in 802.11 MAC?

Accepted Answer

To provide contention-based channel access using CSMA/CA

Answer

To assign fixed time slots to each station

Answer

To allow the AP to poll stations for data

Answer

To prioritize voice traffic over data traffic

Question 2

In 802.11 CSMA/CA, a station must sense the medium idle for a DIFS period before transmitting. What does DIFS stand for?

Accepted Answer

Distributed Inter-Frame Space

Answer

Dynamic Inter-Frame Spacing

Answer

Data Interval Frame Sequence

Answer

Deferred Inter-Frame Slot

Question 3

After detecting the channel is busy, a station invoking binary exponential backoff selects a random number from the contention window. What happens to the contention window size after each successive collision?

Accepted Answer

It doubles up to a defined maximum

Answer

It resets to its minimum value

Answer

It is halved

Answer

It remains constant

Question 4

Which inter-frame space is the SHORTEST and is used to give priority to ACK and CTS frames?

Accepted Answer

SIFS

Answer

DIFS

Answer

PIFS

Answer

AIFS

Question 5

A station completes a successful data frame exchange. According to DCF, what must happen before the receiving station sends an ACK?

Accepted Answer

Wait a SIFS period

Answer

Wait a DIFS period

Answer

Run a backoff timer

Answer

Send a CTS frame first

Question 6

What mechanism does 802.11 MAC use to detect and discard duplicate frames caused by retransmissions?

Accepted Answer

The Sequence Control field and the Retry bit in the MAC header

Answer

CRC check on the frame body

Answer

Comparing source MAC addresses

Answer

The Duration/ID field value

Question 7

Which MAC frame type is responsible for managing 802.11 association and authentication between a client and an AP?

Accepted Answer

Management frames

Answer

Data frames

Answer

Control frames

Answer

Extension frames