Consider a CSMA/CD network that transmits data at the rate of 100 Mbps over a…
2024
Consider a CSMA/CD network that transmits data at the rate of 100 Mbps over a 1 Kilometre cable with no repeater. If the minimum frame size required for this network is 1250 bytes, what is the signal speed (km/sec) in the cable.
- A.
8000
- B.
16000
- C.
12000
- D.
20000
Attempted by 130 students.
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Correct answer: D
Solution:
Convert the minimum frame size to bits: 1250 bytes × 8 = 10000 bits.
Compute the transmission time at 100 Mbps: 10000 bits / 100,000,000 bps = 0.0001 s = 100 μs.
For CSMA/CD the transmission time must be at least the round-trip propagation time, so one-way propagation time ≤ 100 μs / 2 = 50 μs.
Signal speed = distance / one-way_time = 1 km / 50×10⁻⁶ s = 20,000 km/s.
Answer: 20000 km/s.
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