We are sending a file of $500,000$ bits from a source host to a destination

host. All links in the path between source and destination have a

bandwidth of $1Mbps.$ Assume that the propagation speed is $2\mathrm{.}0**{10}^8$

meters$/$sec$,$ and the distance between source and destination is $10,000$

$km.$

a$)$ Initially suppose there is only one link between source and

destination. Suppose the file is sent as one message, what is the

transmit time? $(6)$

b$)$ What is the total transfer time $($transmit time plus propagation delay$)?|$How many bits will the source have transmitted when the first bit

arrives at the destination? $(7$ points$)$

Now suppose there are two links between source and destination, with

one switch connecting the two links. Each link is $5,000$ km long.

Again, suppose the same file is sent as one message. Suppose there is

no congestion, so that the message is transmitted onto the second link

as soon as the router receives the entire message. What is the total

transfer time? $(6$ points$)$