Consider a network message transfer between a source S and a destination D through 3 routers R1, R2 and R3 as shown below:

S -­--­--­--­--­--­--­--­-R1 -­--­--­--­--­--­--­--­--­-R2 -­--­--­--­--­--­--­--­--­-R3 -­--­--­--­--­--­--­--­--­-D

A message M needs to be transferred from S to D. M will be divided into packets, therefore M/packet_sizeis the number of packets. For example, if M is 100 MB, and packet size is 10MB then there will be 10 packets.

Write a simple program to simulate the arrival of a packet at R1, then R2, then R3, and then D, and finally the program should indicate how long it would take for the entire message M to arrive at D.

In the program the user should be able to choose different packet sizes and bandwidths of the links. Ignore processing, queuing and propagation delays.Keep in mind that when the first packet is being sent from R1 to R2, the second packet is being sent from the source host to R1. Now fix the bandwidth of each link to 100Mbps. Run the program for different message sizes and packetsizes.

Draw graphs of total delay time vs. message size and total delay time vs. number of packets.