Question $9$

$($i$)$ Draw schematically the dependence of the congestion window $W_c($in kilobytes$)$

on the transmission time $t($in the RTT units$)$ for congested internet assuming the

following scenario: At $t=33RTT$ the first three duplicate ACKs have been received

by the sender host before the RTO. After this another three duplicate ACKs were

received at $t=67RTT,$ and then at $t=75RTT$ the first RTO of the sender$\text{'}$s

acknowledgement clock has occurred. Between $t=75RTT$ and $t=85RTT$ the

network operates without disruptions. You need to draw the dependence for a time

interval between $t=0$ and $t=85RTT$ and explain in detail each stage of the

congestion window evolution. Assume that at $t=0$ the first packet loss took place

due to the RTO and the initial window size is set to $W_c=MSS=1$ kilobyte. The

slow$-$start threshold for a fully open congestion window is $SS{T}_0=64$ kilobytes.

$($ii$)$ Consider that in the case from part $($i$)$ at $t=85RTT$ the receiver reports to the

sender that its receive window is $W_r=30$ kilobytes, and $W_r$ is kept at this value in the

following transmissions. Find how long it will take $($beginning from $t=85RTT)$

before the full window will be sent. Your answer should be in units of RTT $.$