Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: 1-persistent CSMA provides low delay under low load conditions. Reason R: When the channel is free, stations transmits immediately without any random delay, ensuring quick access and minimal delay. In the light of the above statements, choose the most appropriate answer from the options given below
Assertion A: 1-persistent CSMA Low Delay
The statement asserts that 1-persistent CSMA provides low delay under low load conditions. In a network with low load, collisions between stations transmitting simultaneously are infrequent. Because 1-persistent CSMA transmits immediately upon sensing the channel idle, there is minimal waiting time, leading to low access delay.
Reason R: Immediate Transmission Protocol
The reason explains that when the channel is free, stations transmit immediately without any random delay. This is a defining characteristic of persistent CSMA protocols, including 1-persistent CSMA. This immediate transmission behaviour helps minimize the time stations spend waiting when the network is not congested.
CSMA Explanation: A and R Correctness
Based on the analysis:
- Assertion A is correct: 1-persistent CSMA indeed offers low delay when network traffic (load) is light because the probability of collisions is low.
- Reason R is correct: The protocol's mechanism involves immediate transmission upon sensing an idle channel, bypassing additional random delays.
- Reason R correctly explains Assertion A: The immediate transmission strategy described in R is the direct cause of the low delay mentioned in A, especially under low load where this strategy is most effective.
Therefore, both statements are correct, and Reason R provides the accurate explanation for Assertion A.
Important Questions from Flow Control and Error Control
- Consider the implementation of sliding window protocol over a lossless link, with a window size of $W$ frames, where each frame is of size 1000 bits (including header). The bandwidth of the link is 100 kbps ($1\text{k} = 10^3$) and the one-way propagation delay is 100 milliseconds. Assume that processing times at the sender and receiver are zero and the transmission time of acknowledgements is also zero. Which one of the following options gives the minimum size of $W$ (in number of frames) required to achieve 100% link utilization?
