20. How big is a physical PDU? The answer to this question determines the number of simultaneous transmissions for many network architectures.

If a signal propagates through copper wire at a rate of 2 × 108m/s, then on a carrier running at 10Mbps the length of each bit pulse is given by:
If a data frame is 512 bits long, then the entire frame occupies:
(Length of one bit) × (Frame size) = 20 × 512 = 10,240 meters.

a) How big is a 1,024-bit packet if the network runs at 100Mbps?

b) How big is it if the network speed is increased to 155Mbps?

c) At 100Mbps, how much time elapses as one of these frames passes a particular point in the network?

Transcribed Image Text:

Speed of propagation 2 10m/s Speed of bus 20m/bit 10 x 10 b/s