Question $4$

$($a$)$ Apply Dijkstra's algorithm to compute the shortest path from router R$1$ to each other

router in the network shown in Figure $4\mathrm{.}1.$ The number on each line shows the cost of the

line. Based upon these calculations write down the shortest routes from R$1$ to each other

router, the route cost values, and the first$-$hop router. Your answer should be given in form

of the routing table which will show the path to each router and the corresponding cost.

$($b$)$ What are the most important improvements of the IPv$6$ protocol compared with IPv$4.$ Note,

you are not required to compare IPv$6$ and IPv$4,$ but to give at least $5$ main improvements.

$($c$)$ Two IPv$6$ hosts need to communicate over the Internet. The communication route between

the nodes passes through the IPv$4$ network. Design and explain a scheme which enables

communication between the two IPv$6$ hosts.

$($d$)$ Domain Name System $($DNS$)$ is an example of the client$-$server approach to networking.

DNS transfers all messages using UDP packets. It is known that UDP packets have a

maximum length, which potentially can be as low as $576$ bytes. What do you think will

happen when a DNS name to be resolved exceeds this length? Is this possible in principle?

If no$,$ explain why. If yes, can the DNS message be sent in two $($or more$)$ packets?