In stop-and-wait transmission, suppose that both sender and receiver retransmit their last frame immediately on receipt of a duplicate ACK or data frame; such a strategy is superficially reasonable because receipt of such a duplicate is most likely to mean the other side has experienced a timeout.

(a) Draw a timeline showing what will happen if the first data frame is somehow duplicated but no frame is lost. How long will the duplications continue? This situation is known as the Sorcerer’s Apprentice bug.

(b) Suppose that, like data, ACKs are retransmitted if there is no response within the timeout period. Suppose also that both sides use the same timeout interval. Identify a reasonably likely scenario for triggering the Sorcerer’s Apprentice bug.