Suppose host A reaches host B via routers R1 and R2: A–R1–R2–B.

Fast retransmit is not used, and A calculates TimeOut as 2 × EstimatedRTT. Assume that the A–R1 and R2–B links have infinite bandwidth; the R1−→R2 link, however, introduces a 1-secondper-packet bandwidth delay for data packets (though not ACKs).

Describe a scenario in which the R1–R2 link is not 100% utilized, even though A always has data ready to send. Hint: Suppose A’s CongestionWindow increases from N to N + 1, where N is R1’s queue size.