Fig. $3$ shows a plot of TCP Reno window size as a function of time $($transmission

round$).$A$.$ Identify the interval$($s$)$ of time when TOP slow start is operating. $(5$ marks$)$

B$.$ Identify the interval$($s$)$ of time when TOP congestion avoidance is operating.

$(5$ marks$)$

C$.$ Explain why TOP behaves in this manner at the $4$th transmission round. $(5$ marks$)$

D$.$ What is the value of the TOP slow start Threshold at the $6$th transmission round?