Calculate the total time required to transfer a $1000-$KB file in the following cases, assuming an RTT of $50$ ms$,$ a packet size of $1$ KB data, and an initial $2\backslash$times RTT of $$handshaking$$ before data is sent:

$($a$)$ The bandwidth is $1\mathrm{.}5$ Mbps$,$ and data packets can be sent continuously.

$($b$)$ The bandwidth is $1\mathrm{.}5$ Mbps$,$ but after we finish sending each data packet we must wait one RTT before sending the next.

$($c$)$ The bandwidth is $$infinite$,$ meaning that we take transmit time to be zero, and up to $20$ packets can be sent per RTT$.$

$($d$)$ The bandwidth is infinite, and during the first RTT we can send one packet $(211),$ during the second RTT we can send two packets $(221),$ during the third we can send four $(231),$ and so on$.($A justification for such an exponential increase will be given in Chapter $6.)$

$7.$ What properties of postal addresses would be likely to be shared by a network addressing scheme? What differences might you expect to find? What properties of telephone numbering might be shared by a network addressing scheme?

$8.$ One property of addresses is that they are unique; if two nodes had the same address, it would be impossible to distinguish between them. What other properties might be useful for network addresses to have? Can you think of any situations in which network $($or postal or telephone$)$ addresses might not be unique?

$9.$ Give an example of a situation in which multicast addresses might be beneficial.

$14.$ Suppose a $128-$kbps point$-$to$-$point link is set up between the Earth and a rover on Mars. The distance from the Earth to Mars $($when they are closest together$)$ is approximately $55$Gm$,$ and data travels over the link at the speed of light$3\backslash$times $108$ m$/$s$.$

$($a$)$ Calculate the minimum RTT for the link.

$($b$)$ Calculate the delay $\backslash$times bandwidth product for the link.

$($c$)$ A camera on the rover takes pictures of its surroundings and sends these to Earth. How quickly after a picture is taken can it reach Mission Control on Earth? Assume that each image is $5$Mb in size.