Suppose that host A is connected to host B via an intermediate router R. The link between A and R is instantaneous, but the link between R and B transmits only one packet each second, one at a time. All links are full-duplex so that the two directions transmit independently. Hosts A and B run an ARQ protocol to control the exchange of packets between them. Assume that at time t = 0 host A has 7 frames to send to host B. Assume that the router has a queue size of 1; that is, it can hold one packet in addition to the one it is sending (in each direction). Let As timeout be 6 seconds.

(a) Assume the sliding window protocol with SWS=RWS=3 is utilized between host A and B. Using a diagram show the times that the first 7 frames are transmitted (or retransmitted) and when they are correctly received at host B. Also show what ACKs are sent. (Hint: to check your work the ACK for frame 7 is received at time 11).

(b) Now repeat the same scenario as in part (a) but instead use 3 concurrent logical channels. Provide a diagram like for part (a). (Hint: to check your work the final ACK is received at time 8, and it is not for frame 7!