Computer Networks · TEE · papers
Q1(a) · Store-and-forward delay
2022-11-16 · AI-only Sem V
Exact historical variant. Current-syllabus questions solved; excluded topics and source limitations stated.
Q1(a). A 1000-bit packet crosses three store-and-forward links. Every link has rate 2 Mbps and propagation delay 1 ms. Ignore other delays. Find the end-to-end delay. [5 marks]
Answer
Given
One packet, L=1000 bits;3 links;rate2000000 bits/s;propagation1ms/link;store-and-forward.
To find
Total time until the final packet bit reaches the destination.
Formula and why
LaTeX: T=\sum_{i=1}^{3}(L/R_i+d_{prop,i})Each router must receive the complete packet before sending it onward, so all three serialization times count.
Solution
Step 1. Calculate serialization on one link
1000/2000000 seconds=0.0005s=0.5ms.
Step 2. Add propagation per link
0.5+1=1.5ms.
Step 3. Add all three links
3×1.5=4.5ms. Queuing/processing are ignored as instructed.