Final answer:
In a CSMA/CD network, the frame length should be at least equal to the time it takes for the signal to travel from the sender to the farthest point on the network and back.
Step-by-step explanation:
In a CSMA/CD network, the sender needs to be able to detect collisions in order to avoid data corruption. To detect a collision, the sender needs to be able to detect the collision signal before the entire frame has been transmitted. The length of the frame should be at least equal to the time it takes for the signal to travel from the sender to the farthest point on the network and back. The formula for calculating the minimum frame length is 2 * L / speed of light, where L is the length of the network. In this case, the minimum length of the frame should be approximately 30 meters.
In this case, the collision occurred 20 µs after the first bit of the frame left the sender, which means the sender needs to be able to detect the collision within this time. The time it takes for the signal to travel from one end of the network to the other and back can be calculated using the propagation delay formula:
Propagation delay = 2 * length / speed of light
Since the length of the network is unknown, let's assume the length as 'L'. Therefore, the propagation delay can be written as:
Propagation delay = 2 * L / speed of light
From the given information, we know that the speed of light is approximately 3 × 10^8 meters per second. Setting the propagation delay to be less than or equal to 20 µs, we can solve for the minimum length of the frame:
2 * L / (3 × 10^8 m/s) ≤ 20 µs
Simplifying, we get:
L ≤ (20 µs) * (3 × 10^8 m/s) / 2
Plugging in the values, we find that the minimum length of the frame should be approximately 30 meters.