Problem $3(12$ marks$)$: Consider the following exchange of data frames between host systems A

and $B,$ connected via a full$-$duplex link and using sliding$-$window flow control with $3-$bit sequence

numbers and maximum window size of $W=7$ frames:

a$)$ At each one of the times indicated $($i$.$e$.,t_0,$dots,$t_4),$ list the sequence number of the frames

that may be sent by station A$.$ Present your answer in the form of a table:

b$)$ At each one of the times indicated, list the sequence number of the frames that may be

accepted by station B $($again$,$ present your answer as a table$).$

c$)$ Explain the meaning of the different message types listed below. Specifically, for each

message type, indicate the meaning of the message for the station sending it $($say B$),$ as well

as the action taken by the station receiving it $($say A$).$

RRi used in sliding$-$window flow control.

REJi used in go$-$back$-$N ARQ error control.

SREJi used in selective$-$reject ARQ.