CSMA/CD and Channel Persistence Methods Quiz

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.

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.