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Questions and Answers
What is the inefficiency of CSMA before the implementation of CSMA/CD?
How does CSMA/CD overcome the inefficiency of CSMA?
In CSMA/CD, what action should a station take if a collision is detected during transmission?
How does a node detect a collision in CSMA/CD?
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What should a station do after sending a jam signal in CSMA/CD?
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What role does the CSMA persistence algorithm play in the CSMA/CD protocol?
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What is the maximum throughput for Pure Aloha according to the text?
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In CSMA, what is considered the vulnerable time that affects protocol performance?
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Which CSMA protocol involves a station waiting a random amount of time after the medium is detected busy to re-attempt transmission?
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What is the impact of longer propagation delay on CSMA protocol performance?
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What factor in local area networks can help reduce the possibility of collisions in CSMA?
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Which type of CSMA protocol specifies that a station should transmit immediately after the medium becomes idle?
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What is the main difference between 1-persistent and p-persistent CSMA protocols?
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How does non-persistent CSMA handle idle medium?
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Why is bandwidth wasted if waiting time (back off) is large in non-persistent CSMA?
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What characteristic describes 1-persistent stations in CSMA?
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In p-persistent CSMA, what does a station do if the medium is idle?
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What does 1-persistent CSMA guarantee when two or more stations become ready to transmit simultaneously?
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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.