Consider the implementation of sliding window protocol over a lossless link,…
2026
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 (1k = 103) 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?
- A.
10
- B.
21
- C.
20
- D.
11
Attempted by 81 students.
Show answer & explanation
Correct answer: B
Solution
Given:
Frame size = 1000 bits
Bandwidth = 100 kbps
Propagation delay = 100 ms
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Step 1: Transmission Time
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Transmission time:
Tt = Frame Size / Bandwidth
= 1000 / (100 x 10^3)
= 0.01 s
= 10 ms
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Step 2: Propagation Delay Ratio
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Propagation delay:
Tp = 100 ms
Compute:
a = Tp / Tt
= 100 / 10
= 10
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Step 3: Window Size Formula
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For 100% utilization in sliding window protocol:
W >= 1 + 2a
Substitute value of a:
W >= 1 + 2(10)
W >= 21
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Final Answer
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Minimum window size required:
W = 21 frames
Correct Option: 21
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