Question

Consider a point-to-point link 10 km in length. At what bandwidth would propagation delay (at the speed of 2×108m/s) equal transmit delay for 125-byte packets? What about 640-byte packets?

Answer 1

For 125-byte packets:

Transmission delay = Packet size/ Bandwidth

Propagation delay = Distance/Propagation speed

Propagation speed = 2 × 10^8 m/s

Let's assume that the transmission delay is equal to the propagation delay:

Packet size/Bandwidth = Distance/Propagation speed

Bandwidth = Packet size * Propagation speed / Distance

Bandwidth = 125 * 2 × 10^8 / 10,000 = 2.5 × 10^6 bps or 2.5 Mbps

For 640-byte packets:

Bandwidth = Packet size * Propagation speed / Distance

Bandwidth = 640 * 2 × 10^8 / 10,000 = 12.8 × 10^6 bps or 12.8 Mbps.