Project ForgeComputer Networks
OSI/TCP-IP Layers & Routing
GATE 2013
Hard
Determine the maximum length of the cable (in km) for transmitting data at a rate of 500 Mbps in an Ethernet LAN with frames of size 10,000 bits. Assume the signal speed in the cable to be 2,00,000 km/s.
- A1
- 2
- C2.5
- D5
Explanation
Transmission time Tt = frame size / rate = 10000/(500×10⁶) = 20 μs. For reliable collision detection (CSMA/CD), we need Tt ≥ 2×Tp, so max propagation delay Tp = Tt/2 = 10 μs. Max distance = speed × Tp = 200,000 km/s × 10×10⁻⁶ s = 2 km.
Source: GATE CS 2013 (2013)
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