ITPEC FE Morning April 2021 Question 30

Network Response Time Calculation — compute round-trip response time from transmission parameters.

Given:
- Line speed: 8 Mbit/s, efficiency: 60%
- Upload: 1 MB, Download: 2 MB (1 MB = 10⁶ bytes)
- Client processing: 0.4 s total, Server processing: 0.4 s total
- Propagation delay: ignored

Step 1 — Effective throughput:
- 8 × 0.6 = 4.8 Mbit/s
- In bytes: 4.8 × 10⁶ / 8 = 0.6 × 10⁶ bytes/s = 0.6 MB/s

Step 2 — Transmission times:
- Upload: 1 MB ÷ 0.6 MB/s = 5/3 ≈ 1.667 s
- Download: 2 MB ÷ 0.6 MB/s = 10/3 ≈ 3.333 s

Step 3 — Total response time:
- Transmission: 5/3 + 10/3 = 15/3 = 5.0 s
- Processing: 0.4 + 0.4 = 0.8 s
- Total: `5.0 + 0.8 = 5.8 s`

Answer: `d) 5.8`

Why not others:
- (a) 1.4 — only accounts for partial transmission
- (b) 3.8 — likely miscalculates efficiency or ignores one direction
- (c) 5.0 — includes only transmission time, forgetting processing times

Key rule: Response time = upload_time + download_time + client_processing + server_processing. Processing times are sequential (not overlapping with transmission).

AI-generated — may contain errors