The network using CSMA/CD has a bandwidth of 20 mbps. If the maximum propagation time is 25μ sec (microsecond), what is the minimum size of the frame?

The correct answer is 2) 1000 bits.

Key Points

• The network uses CSMA/CD, which stands for Carrier Sense Multiple Access with Collision Detection.
• To determine the minimum frame size in a CSMA/CD network, we need to ensure that the transmission time is at least twice the maximum propagation delay. This is to detect collisions before the entire frame is transmitted.
• Given:
  • Bandwidth (B) = 20 Mbps
  • Maximum Propagation Time (T) = 25 μs
• The minimum frame size (S) can be calculated using the formula: S = 2 * B * T
• Calculating the minimum frame size:
  • S = 2 * 20 Mbps * 25 μs
  • Converting units: 1 Mbps = 10^6 bits per second and 1 μs = 10^-6 seconds
  • S = 2 * 20 * 10^6 bits/second * 25 * 10^-6 seconds
  • S = 2 * 20 * 25 bits
  • S = 1000 bits
• However, the actual minimum frame size to avoid collision detection issues is often standardized, and in this case, it is 1000 bits.

Additional Information

• CSMA/CD is used in Ethernet networks to manage the transmission of data and avoid collisions. The calculation ensures that the round-trip time for a signal to propagate across the network and back is taken into account.
• Understanding frame size calculations is crucial for network design and ensuring efficient data transmission.