Question

1. Host A and Host B are connected by a network with 2 store-and-forward switches. Each link has a bandwidth of 5 megabits/second and is 1,000 kilometers long. The network propagation speed is 200,000 kilometers/second. Host A sends 10,000-bit packets to Host B. Give proper units on each answer. (For these and other numerical problems it is required that you give a formula, using numbers from the problem, that can be evaluated to give the numerical answer.)

a) What is the round-trip propagation delay between A and B?

b) What is the transmission delay of a single packet from A to B?

c) What is the bandwidth-delay product between A and B (RTT)?

Answer 1

Sol.

Host A and Host B

Given that bandwidth B = 5 megabits/sec

= 5 * 10⁶ bits/sec

that means host A a transmit 5000000 bits per second to Host B

In 1 second transmitted bits = 5000000

so 1 bit transmission time = 1/5000000

= 0.2 * 10^-6 = 2 Microsecond

given packets size = 10,000

so to transnsmit 10,000 the time will be = 0.2 * 10^-6 * 10,000

= 2 * 10^-3 = 2mili sec

so Trasmission Delay = T_t = 2ms

Propogation Delay = T_p = d/v = 1000/200000

= 5 milisec

Now, RTT = Round Trip Time = 2*T_p + T_t

= 2 * 5ms + 2ms

= 12 ms

RTT = 12 milisec

Trasmission Delay = T_t = 2milisec

Propogation Delay = T_p = 5 milisec

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