Questions#$2$:

Consider the following situation, which involves four separate servers connecting to four different

clients over four three$-$hop paths between servers and clients. The four pairings have a common

intermediate hop with a transmission capacity of $R=200Mbps.$ The four links between the servers and

the shared link have a transmission capacity of $R_S=60Mbps.$ Each of the four links between the shared

middle link and a client has a transmission capacity of $R_C=20Mbps.$

a$)$ What is the maximum attainable end$-$to$-$end throughput $($in Mbps$)$ for each of four client$-$server

pairs, assuming that the intermediate link capacity is shared fairly among all the pairs?

b$)$ Which link in the above scenario forms the bottleneck $(R_s,R,$ or $R_s)?$ What does this mean?

c$)$ Assuming that the servers are sending at a rate of $20$ Mbps $,$ what are the link utilizations for the

server links $(R_s)?$

d$)$ Assuming that the servers are sending at a rate of $20,$ what are the link utilizations for the client

links $(R_s)?$

e$)$ Assuming that the servers are sending at the maximum rate possible, what is the link

utilizations for the shared link $(R)?$

f$)$ Assume a file of $2$ Gbits is being sent from one of the servers at one end of the connection to

the client at the other end of the connection. What is the estimated time taken to send the file?

g$)$ Why is it important to avoid having the Internet link at the network core as a bottleneck?