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 * 10^8 m/s. The minimum frame size for this network should be: A. 10000 bits B. 10000 bytes C. 5000 bits D. 5000 bytes

GATE 2005 · Computer Networks · CSMA CD · medium

Answer: Minimum frame size = 10000 bits. Answer: A.

  1. Compute one-way propagation delay: t_p = 1000 m / (2 * 10^8 m/s) = 5 * 10^-6 s = 5 microseconds
  2. Compute round-trip propagation delay: RTT = 2 * 5 * 10^-6 = 10 * 10^-6 s = 10 microseconds
  3. Compute minimum frame size: min_frame_size = 10^9 bits/s * 10^-5 s = 10^4 bits = 10000 bits