Networking:

Suppose two hosts A and B are directly connected. The propagation speed through the direct connection is 2.2*108 meters per second. The distance between the two hosts is 4500 m. The transmission rate supported by the direct connection is 16 Mbps (1 Mbit = 220 bits). A user has a 4.5 Gb (4.5*230 bits) file to transfer across the connection.

a) What is the propagation delay?

b) What is the maximum number of bits that have left A before the first bit arrives at B? This number of bits is called the bandwidth delay product.

c) We can think of each bit occupying a piece of the link. If the bandwidth delay product tells us that there are 100 bits in the transmission medium then we can think of each bit occupying 1/100 of the length of the transmission media. What is the width of each bit (the length of the transmission medium it fills)?

d) Assume that the file is sent as a single message (not broken into packets). What is the transmission time of the file?

Now consider that the connection between A and B is through a packet switched network. Message segmentation is the process of our file (or any other message) into smaller sections and sending each of those sections in a separate packet. Assume that each link in the packet switched network has a capacity of 100Mbps, the propagation delay on each link is 0.002s, the processing delay on each link is 0.003s, there are no queuing delays, and the packet is transmitted by A and by 9 additional hosts as it travels through the packet switched network to B.

e) Consider sending the file through the packet switched network without message segmentation (as a single packet). Assume that each of the intermediate hosts is store and forward nodes. How long does it take to send the file from A to B?

f) Assume that the file is segmented into packets containing 12000 bits of data each. Each packet has a header of 200 bits. If a packet is partially full of data the remainder of the data field is filled with zeros before the resulting full-size packet is transmitted. How long does it take for the file to be transmitted through the network (assume no queuing delays)?

g) What is the optimal packet size to transmit this file through this network.