L16. Describe CSMA/CD and how it differs from CSMA/CA.

Question 1

What is CSMA/CD?

Answer 1

Carrier Sense Multiple Access with Collision Detection is a link layer protocol that controls how data packets are transmitted over a shared medium

Question 2

What is CSMA/CA?

Answer 2

Carrier Sense Multiple Access with Collision Avoidance is a link layer protocol that controls how data packets are transmitted over a shared medium

Question 3

What are common properties of CSMA/CD and CSMA/CA?

Answer 3

They both control how data packets are transmitted over a shared medium in order to minimize collisions and improve network efficiency

Question 4

What is the main difference between CSMA/CD and CSMA/CA?

Answer 4

They operate in different network environments

Question 5

What type of network is CSMA/CD typically used in?

Answer 5

CSMA/CD is primarily used in wired Ethernet networks

Question 6

What is Carrier Sensing?

Answer 6

A device listens to the network to check if it is currently free (i.e., no other device is transmitting) before transmitting data.

Question 7

What is Multiple Access?

Answer 7

The device beginning transmission if the network is idle or waiting and retrying after a random backoff period if it’s busy.

Question 8

What is Collision Detection?

Answer 8

The device monitoring the network to detect collisions. A collision occurs when two devices transmit simultaneously, causing the signals to interfere.

Question 9

How does CSMA/CD handle collisions?

Answer 9

Upon detecting a collision, the device immediately stops transmitting and sends a jamming signal to inform all devices of the collision. Both devices involved in the collision then wait for a random backoff time before attempting to retransmit.

Question 10

What type of network is CSMA/CA typically used in?

Answer 10

CSMA/CA is used in wireless networks, such as Wi-Fi.

Question 11

How does CSMA/CA handle collision, in contrast to CSMA/CD?

Answer 11

Unlike CSMA/CD, CSMA/CA aims to avoid collisions before they happen

Question 12

Why is Collision Avoidance important in wireless networks?

Answer 12

Detecting collisions is difficult due to the hidden node problem and signal attenuation.

Question 13

What is Collision Avoidance?

Answer 13

The device waiting for an additional, randomized period called the Inter-Frame Space (IFS) before transmitting even if the medium is free. This reduces the chance that multiple devices will start transmitting simultaneously.

Question 14

What does CSMA/CA do to further avoid collisions?

Answer 14

It uses Request to Send/Clear to Send (RTS/CTS) frames. The device sends an RTS frame to the intended receiver, which responds with a CTS frame if the medium is clear. Other devices that hear these frames defer their transmissions.

Question 15

How does CSMA/CA detect and handle collisions?

Answer 15

After successfully receiving data, the receiver sends an acknowledgment (ACK) to the sender. If no ACK is received, the sender assumes a collision occurred and retries transmission.

Question 16

Name the four main differences between CSMA/CD and CSMA/CA

Answer 16

1. Collision Handling: CSMA/CD detects collisions during transmission and handles them post-facto, while CSMA/CA attempts to avoid collisions before they occur.
2. Environment: CSMA/CD is used in wired Ethernet networks where collision detection is feasible, while CSMA/CA is used in wireless networks where collision detection is difficult or impractical.
3. Mechanisms: CSMA/CD relies on collision detection and jamming signals to manage network access, while CSMA/CA uses random backoff intervals and optional RTS/CTS frames to prevent collisions.
4. Efficiency: CSMA/CD becomes less efficient as network load increases, while CSMA/CA is better suited for environments with higher potential for collisions due to multiple access points and mobile devices.