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GATE 2014 CS (CS2) – Question 36

Computer Networks · Basics of Switching and Performance Metrics · 2 marks · Multiple choice

A store-and-forward network A—R1—R2—B has bandwidth 10⁶ bytes/s on every link. A 10³-byte file is sent three ways: one packet (time T₁), 10 equal packets (T₂), or 20 equal packets (T₃), back-to-back. Each packet adds a 100-byte header. Consider only transmission time; ignore processing, queueing, propagation and errors. Which is correct?

  1. T₁ < T₂ < T₃
  2. T₁ > T₂ > T₃
  3. T₂ = T₃, T₃ < T₁
  4. T₁ = T₃, T₃ > T₂

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Correct answer: (D) T₁ = T₃, T₃ > T₂

Explanation

For kpackets over3links, total time is(k+2)(1000/k+100)/10⁶seconds. For k=1,10,20 this gives3300μs,2400μs,3300μs. Thus **T1=T3>T2,D**. Packetisation enables pipelining but smaller packets add more100byte headers.