GATE | GATE IT 2005 | Question 71

A network with CSMA/CD protocol in the MAC layer is running at 1 Gbps over a 1 km cable with no repeaters. The signal speed in the cable is 2 x 10⁸ m/sec. The minimum frame size for this network should be

 
(A) 10000 bits
(B) 10000 bytes
(C) 5000 bits
(D) 5000 bytes


Answer: (A)

Explanation:

Frame Size S >= 2BL/P

Where,

Cable Length L = 1KM = 1000M 
Propogation Speed P = 2 x 10^8 m/sec
Bandwidth = 1 Gbps = 10^9 bps

See this for details of above formula.

S >= (2 *  10^9 * 1000) / (2 x 10^8)
  >= 10000 bits

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