1. EE 122 Discussion Section XI 17 th November Sameer Agarwal

2. 2 1a. Vanilla TCP segment 1 SS:cwnd = 1 ACK 2 SS:cwnd = 2 segment 2 segment 3 ACK 4 SS:cwnd = 4 segment 4 segment 5 segment 6 segment 7 ACK 4 ACK 3ACK 4 segment 4 Timeout! Set SS thresh SS:cwnd = 1 ACK 8 SS:cwnd = 2 segment 8 segment 9 ACK 10 AIMD:cwnd = 3 ACK 9 segment 10 segment 11 segment 12

3. 3 1b. TCP+ Fast Retransmission segment 1 SS:cwnd = 1 ACK 2 SS:cwnd = 2 segment 2 segment 3 ACK 4 SS:cwnd = 4 segment 4 segment 5 segment 6 segment 7 ACK 4 ACK 3ACK 4 segment 4 3 Dup ACKs! Set SS thresh SS:cwnd = 1 ACK 8 SS:cwnd = 2 segment 8 segment 9 ACK 10 AIMD:cwnd = 3 ACK 9 segment 10 segment 12 segment 11

4. 4 1c. TCP+ Fast Retransmission & Fast Recovery segment 1 SS:cwnd = 1 ACK 2 SS:cwnd = 2 segment 2 segment 3 ACK 4 SS:cwnd = 4 segment 4 segment 5 segment 6 segment 7 ACK 4 ACK 3ACK 4 segment 4 3 Dup ACKs! Set SS thresh AIMD:cwnd = 2 ACK 8 AIMD:cwnd = 3 segment 8 segment 9 ACK 10 AIMD:cwnd = 4 ACK 9 segment 10 segment 12 segment 11 ACK 11

5. 5 Repeating Slow Start After Timeout t Window Slow-start restart: Go back to CWND of 1 MSS, but take advantage of knowing the previous value of CWND. Slow start in operation until it reaches half of previous CWND, I.e., SSTHRESH Timeout Fast Retransmission SSThresh Set to Here