Draw a timeline diagram for the sliding window algorithm with SWS = RWS = 4 frames in the following two situations. Assume the receiver sends a duplicate acknowledgment if it does not receive the expected frame. For example, it sends DUPACK[2] when it expects to see Frame[2] but receives Frame[3] instead. Also, the receiver sends a cumulative acknowledgment after it receives all the outstanding frames. For example, it sends ACK[5] when it receives the lost frame Frame[2] after it already received Frame[3], Frame[4], and Frame[5].

Use a timeout interval of about 2 × RTT.

(a) Frame 2 is lost. Retransmission takes place upon timeout (as usual).

(b) Frame 2 is lost. Retransmission takes place either upon receipt of the first DUPACK or upon timeout. Does this scheme reduce the transaction time? (Note that some end-to-end protocol

[e.g., variant of TCP] uses a similar scheme for fast retransmission.)