Module05_-_deck_1

What is the main purpose of Medium Access Control (MAC)?

To provide controlled and efficient access to the network medium.

What are the two forms of contention commonly used in networks?

CSMA/CD (Carrier Sense Multiple Access with Collision Detection) and CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance).

What is CSMA/CD primarily used for?

It is used for 802.3 Ethernet networks.

How does a CSMA/CD node handle a collision?

It calculates a random amount of time to wait before attempting to transmit again.

Why do 802.11 wireless networks use CSMA/CA instead of CSMA/CD?

Because 802.11 wireless radios cannot detect collisions since they cannot transmit and receive simultaneously.

What is the Distributed Coordination Function (DCF)?

The fundamental access method of 802.11 communications based on the CSMA/CA process.

List the four main components of the CSMA/CA process in DCF.

Physical carrier sense, virtual carrier sense, pseudo-random backoff timer, and interframe spaces.

What are the two purposes of physical carrier sense?

To detect inbound frames and to check if the medium is busy before transmission.

What does the Duration/ID field in the MAC header signify?

It represents the time required to transmit an active frame exchange process.

What is the role of the Network Allocation Vector (NAV)?

To maintain a prediction of future traffic on the medium based on previous frame information.

What is pseudorandom backoff time?

The time a station waits before attempting to transmit again, selected randomly from a contention window.

What happens to the contention window (CW) size after unsuccessful transmissions?

It increases exponentially up to a maximum value.

What is the difference between SIFS and DIFS?

SIFS is shorter and used for higher priority frames like ACK, while DIFS is longer and used for most other frames.

What does the Hybrid Coordination Function (HCF) enhance?

It enhances DCF with quality-of-service (QoS) capabilities.

What does the Enhanced Distributed Channel Access (EDCA) define?

Four access categories based on priority for different types of data traffic.

What is the purpose of the Wi-Fi Multimedia (WMM) certification?

To prioritize different classes of application traffic during the medium contention process.

How does airtime fairness differ from equal opportunity allocation?

It allocates equal time to devices rather than equal opportunity to access the medium.

What technique does CSMA/CA use to avoid collisions?

Carrier sense to check if the medium is busy and collision avoidance strategies.

What is the correlation of the Energy Detect (ED) threshold in relation to Signal Detect (SD)?

ED is set to 20 dB above the SD threshold.

What happens when the NAV timer is not zero for a station?

The station cannot contend for the medium or transmit.

Why is the backoff timer crucial in wireless transmission?

To ensure that multiple radios take turns in accessing the RF medium.

What is an example of how EDCA prioritizes access categories?

Frames with the highest-priority access category have the lowest backoff values.