$(20$ points$)$ Consider a local network consisting of a source computer connected to an edge router that connects to

a wide area network which routes packets through one backbone router to the destination edge router to the

destination local area network and destination computer.

Assume

Data rate is R$=100$Mbps

Distance from computer to edge router $=1$km

Distance from edge router to backbone router $=15$km

Signal Propagation speed is $2\mathrm{.}8*10^8$ m$/$s

ACK packet size $=54$Bytes

There are no queueing delays and packet$-$processing delays are negligible $($zero$).$

a$.$ Sketch the network topology.

b$.$ Calculate the latency to successfully deliver one VoIP packet with $640$Byte payload $($as described in

Problem $3.$b$.$ above$)$ from the source to the source$$s edge router, where a successful delivery is indicated

by the successful return of an ACK packet.

c$.$ Suppose the probability that a packet is successfully delivered on one link is $50\%.$ Re$-$calculate the latency

and link efficiency from a$.$ and b$.$

d$.$ Calculate the latency to successfully deliver one VoIP packet with $640$Byte payload $($as described in

Problem $3.$b above$)$ from the source all the way to the destination, where a successful delivery is

indicated by the successful return of all ACK packets. Assume the acknowledgements are hop$-$by$-$hop, I.e$.,$

each device that receives a packet returns an ACK packet.

$5.(20$ points$)$ Assuming the network topology and parameters are the same as provided in problem $4$ above...

a$.$ Calculate the link efficiency for the link between the source and the source$$s edge router.

b$.$ Calculate the link efficiency for the end$-$to$-$end link from the source computer to destination computer.

c$.$ Suppose the probability that a packet is successfully delivered on one link is $50\%.$

i$.$ Re$-$calculate the latency from part d$.$

ii$.$ Re$-$calculate the link efficiency from part d$.$