Question

Consider a CSMA/CD network that transmits data at a rate of 100 Mbps (108 bits per second) over a 1 km (kilometer) cable with no repeaters. If the minimum frame size required for this network is 1250 bytes, what is the signal speed (km/sec) in the cable?

1. 8000
2. 10000
3. 16000
4. 20000

Answer 1

Correct Answer - Option 4 : 20000

B = 10⁸ bits/sec

d = 1 km

Road trip distance = 2 km

To detect a collision, sender must be transmitting when it receives the collision signal, so that it can transmit again.

\(\begin{array}{l} \therefore \frac{{1250 \times 8}}{{{{10}^8}}} = \frac{2}{{speed}}\\ \therefore speed = \frac{{2 \times {{10}^8}}}{{{{10}^4}}} = 2 \times {10^4} \end{array}\)