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CSMA/CD and Channel Persistence Methods Quiz
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CSMA/CD and Channel Persistence Methods Quiz

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Questions and Answers

What is the inefficiency of CSMA before the implementation of CSMA/CD?

  • Unstable channel until all packets are transmitted (correct)
  • Channel congestion due to multiple access
  • Constant channel idle time
  • Low data transmission rate
  • How does CSMA/CD overcome the inefficiency of CSMA?

  • By increasing the data transmission rate
  • By listening to the medium continuously
  • By reducing channel wastage during collisions
  • By aborting transmission after a collision (correct)
  • In CSMA/CD, what action should a station take if a collision is detected during transmission?

  • Abort transmission and send a jam signal (correct)
  • Broadcast a retransmission request to other stations
  • Continue transmission at a higher power
  • Increase the data packet size
  • How does a node detect a collision in CSMA/CD?

    <p>By listening to the medium for its own signal</p> Signup and view all the answers

    What should a station do after sending a jam signal in CSMA/CD?

    <p>Back off and wait for a random amount of time</p> Signup and view all the answers

    What role does the CSMA persistence algorithm play in the CSMA/CD protocol?

    <p>Manages the detection and handling of collisions</p> Signup and view all the answers

    What is the maximum throughput for Pure Aloha according to the text?

    <p>1.5</p> Signup and view all the answers

    In CSMA, what is considered the vulnerable time that affects protocol performance?

    <p>Maximum propagation time</p> Signup and view all the answers

    Which CSMA protocol involves a station waiting a random amount of time after the medium is detected busy to re-attempt transmission?

    <p>Non-Persistent CSMA</p> Signup and view all the answers

    What is the impact of longer propagation delay on CSMA protocol performance?

    <p>Worse performance</p> Signup and view all the answers

    What factor in local area networks can help reduce the possibility of collisions in CSMA?

    <p>Immediate knowledge of frame transmission</p> Signup and view all the answers

    Which type of CSMA protocol specifies that a station should transmit immediately after the medium becomes idle?

    <p>1-Persistent CSMA</p> Signup and view all the answers

    What is the main difference between 1-persistent and p-persistent CSMA protocols?

    <p>1-persistent protocol waits until the medium becomes idle, while p-persistent protocol transmits immediately with a probability of p.</p> Signup and view all the answers

    How does non-persistent CSMA handle idle medium?

    <p>Back off and wait a random amount of time</p> Signup and view all the answers

    Why is bandwidth wasted if waiting time (back off) is large in non-persistent CSMA?

    <p>Medium remains idle following the end of transmission</p> Signup and view all the answers

    What characteristic describes 1-persistent stations in CSMA?

    <p>Transmit immediately with probability 1</p> Signup and view all the answers

    In p-persistent CSMA, what does a station do if the medium is idle?

    <p>Transmit immediately</p> Signup and view all the answers

    What does 1-persistent CSMA guarantee when two or more stations become ready to transmit simultaneously?

    <p>Collision will occur</p> Signup and view all the answers

    Study Notes

    CSMA Inefficiencies

    • CSMA (Carrier Sense Multiple Access) can lead to collisions when multiple stations transmit simultaneously without coordination.
    • Before CSMA/CD, collisions resulted in packet loss without any mechanism to manage or detect them.

    CSMA/CD Improvements

    • CSMA/CD (Carrier Sense Multiple Access with Collision Detection) introduces a method for detecting collisions during transmission.
    • It allows stations to recognize when a collision occurs and stop transmitting, reducing wasted bandwidth.

    Actions During Collision in CSMA/CD

    • Upon detecting a collision, a station should immediately cease transmission and send a jam signal to inform all other stations of the collision.

    Collision Detection in CSMA/CD

    • Nodes detect collisions by monitoring the channel while transmitting. If the signal observed differs from the transmitted signal, a collision is confirmed.

    Post-Jam Signal Actions in CSMA/CD

    • After sending a jam signal, stations enter a back-off period, during which they wait before attempting to retransmit.

    Role of CSMA Persistence Algorithm

    • The CSMA persistence algorithm determines how stations behave when the medium is busy, influencing the timing of retransmissions following a back-off.

    Maximum Throughput of Pure Aloha

    • Pure Aloha achieves a maximum throughput of about 18.4%, which is significantly lower than more efficient protocols due to its high collision rates.

    Vulnerable Time in CSMA

    • The vulnerable time in CSMA refers to the duration during which collisions can occur, significantly affecting protocol performance, especially during busy network conditions.

    Random Wait in CSMA Protocols

    • Non-persistent CSMA involves stations waiting a random period before reattempting transmission once the medium is busy, reducing collision chances.

    Impact of Longer Propagation Delay

    • Longer propagation delays can degrade CSMA performance by increasing the likelihood of collisions since stations may not detect transmissions in time.

    Reducing Collisions in Local Area Networks

    • Implementing techniques like segmenting networks or introducing switches can reduce collision occurrences in local area networks using CSMA protocols.

    Immediate Transmission in CSMA Protocol

    • In 1-persistent CSMA, a station transmits instantaneously when the medium becomes idle, prioritizing immediacy over consideration for ongoing traffic.

    1-Persistent vs. P-Persistent CSMA

    • The main difference is that 1-persistent CSMA guarantees immediate transmission upon the medium's availability, while p-persistent CSMA has a probability-based approach for transmission, introducing delays.

    Non-Persistent CSMA Idle Medium Handling

    • Non-persistent CSMA requires stations to sense the medium and, if busy, wait a random duration before checking again, improving efficiency but possibly wasting time.

    Bandwidth Wastage in Non-Persistent CSMA

    • Large waiting times in back-off periods can lead to significant bandwidth wastage, as stations spend extended periods not transmitting while waiting for the medium to become free.

    Characteristics of 1-Persistent CSMA Stations

    • 1-persistent CSMA stations always attempt to transmit immediately upon detecting an idle medium, which can lead to increased collisions when multiple stations act simultaneously.

    Actions in P-Persistent CSMA

    • In p-persistent CSMA, if the medium is idle, a station transmits with a predefined probability, introducing randomness into the process to mitigate collisions.

    Guarantee of 1-Persistent CSMA during Simultaneous Ready States

    • 1-persistent CSMA guarantees that when multiple stations are ready to transmit, at least one will successfully get through, potentially resulting in collisions.

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    Description

    Test your knowledge on CSMA/CD (Carrier Sense Multiple Access with Collision Detection) and different channel persistence methods in networking. Topics include reducing collisions, channel idle time, and the inefficiencies of CSMA.

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