Sharing resources¶
Multiple choice questions¶
- Which of the following affirmations are valid for the ALOHA Medium Access Control scheme ? Select all the valid ones.
ALOHA uses acknowledgements to confirm the correct reception of frames.
In ALOHA, a collision can occur when several hosts transmit almost at the same time.
With ALOHA, a host always listens before transmitting its frame.
- Which of the following affirmations are valid for the CSMA Medium Access Control scheme ? Select all the valid ones.
When using CSMA, a host always listens to the communication channel while transmitting to detect collisions
With CSMA, collisions are detected thanks to the expiration of a retransmission timer.
With non-persistent CSMA, a host checks at random times whether the communication channel when it needs to transmit.
- Which of the following affirmations are valid for CSMA/CD ? Select the correct ones.
To be able to detect all collisions, CSMA/CD must enforce a minimum size for all transmitted frames.
With CSMA/CD, there is no need to use acknowledgements to detect collisions.
CSMA/CD relies on explicit acknowledgements to detect collisions.
- Which of these Medium Access Control algorithms rely on explicit acknowledgements to detect collisions ? Select all the valid answers.
CSMA/CD
CSMA/CA
slotted ALOHA
CSMA
- Consider a network that is using CSMA/CD. An important parameter in such networks is the minimum frame size. Which of the following affirmations is true ?
If the shared medium has a bandwidth of 10 Mbps and a length of 2 kilometers, then the minimum frame size is 200 bits.
The minimum frame size is always set to 512 bits or 64 bytes.
If the shared medium has a bandwidth of 100 Mbps and a length of 1 kilometer, then the minimum frame size is 10000 bits.
- CSMA/CA is a Medium Access Control scheme used in wireless networks. Only a few of the affirmations below concerning CSMA/CA are correct. Which ones ?
CSMA/CA uses explicit acknowledgements to ensure that the frames are correctly received by their destination.
The CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) enables the hosts to prevent all collisions.
CSMA/CA hosts must listen to the communication channel before transmitting.