Networking
10 seconds
10-Second Challenge: Undersea Cable Delay
Ten seconds. Go. How long does a bit take to cross 3000 km?
Quick check · tap an answer to continue
Lesson notes
Calculate transmission and propagation delay and distinguish bandwidth from throughput
Key points
- Propagation delay equals distance divided by speed: 3×10⁶ m ÷ 2×10⁸ m/s.
- That gives 0.015 seconds, which is 15 milliseconds, whatever the bandwidth is.
Takeaway: Propagation delay = distance ÷ speed; bandwidth doesn't affect it.
Quick check: A cable from Accra is 3000 km long; signal speed is 2×10⁸ m/s. What is the propagation delay?
- 15 ms
- 1.5 ms
- 150 ms
Distance over speed, not size over bandwidth; bandwidth never changes propagation delay.
bandwidthlatencythroughputpropagation delay
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