Suppose two nodes, A and B, are attached to opposite ends of an 800 m cable, and that they each have one frame of 1, 500 bits (including all headers and preambles) to send to each other.

Both nodes attempt to transmit at time t = 0. Suppose there are four repeaters between A and B, each inserting a 20-bit delay.

Assume the transmission rate is 100 Mbps, and CSMA/CD with backoff intervals of multiples of 512 bits is used.

After the first collision, A draws K = 0 and B draws K = 1 in the exponential backoff protocol. Ignore the jam signal and the 96-bit time delay.

What is the one-way propagation delay (including repeater delays) between A and B in seconds?

Assume that the signal propagation speed is 2.10⁸ m/sec.

At what time (in seconds) is A's packet completely delivered at B?

Now suppose that only A has a packet to send and that the repeaters are replaced with switches.

Suppose that each switch has a 20-bit processing delay in addition to a store-and-forward delay. At what time, in seconds, is A's packet delivered at B?