Computer Networks · TEE · papers
Q1(b) · Store-and-forward delay
2024-12-06 · AI-only Sem V variant
Exact historical variant. Current-syllabus questions solved; excluded topics and source limitations stated.
Q1(b). A 2000-bit packet crosses three store-and-forward links, each 1 Mbps with propagation delay 2 ms. Ignore other delays. Find end-to-end delay. [5 marks]
Answer
Given
One packet, L=2000 bits;3 links;rate1000000 bits/s;propagation2ms/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
2000/1000000 seconds=0.002s=2ms.
Step 2. Add propagation per link
2+2=4ms.
Step 3. Add all three links
3×4=12ms. Queuing/processing are ignored as instructed.