// Establish connection
0   socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+0  setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+0  bind(3, ..., ...) = 0
+0  listen(3, 1) = 0

// handshake part

// syn
+0  < S 0:0(0) win 32792 <mss 1000,nop,nop,sackOK,nop,wscale 7>
// syn+ack
+0 > S. 0:0(0) ack 1 win 65535 <...>
// ack
+0  < . 1:1(0) ack 1 win 32792

// application phase
+0 accept(3, ..., ...) = 4

// ---- inflate cwnd to 40 segments via ACKs (slow-start phase) ----
+0 write(4, ..., 20000) = 20000

+0 > . 1:1001(1000) ack 1
+0 > . 1001:2001(1000) ack 1
+0 > . 2001:3001(1000) ack 1
+0 > . 3001:4001(1000) ack 1
+0 > . 4001:5001(1000) ack 1
+0 > . 5001:6001(1000) ack 1
+0 > . 6001:7001(1000) ack 1
+0 > . 7001:8001(1000) ack 1
+0 > . 8001:9001(1000) ack 1
+0 > . 9001:10001(1000) ack 1
+.010 < . 1:1(0) ack 10001 win 65535

+0 > . 10001:11001(1000) ack 1
+0 > . 11001:12001(1000) ack 1
+0 > . 12001:13001(1000) ack 1
+0 > . 13001:14001(1000) ack 1
+0 > . 14001:15001(1000) ack 1
+0 > . 15001:16001(1000) ack 1
+0 > . 16001:17001(1000) ack 1
+0 > . 17001:18001(1000) ack 1
+0 > . 18001:19001(1000) ack 1
+0 > P. 19001:20001(1000) ack 1
+.010 < . 1:1(0) ack 20001 win 65535

// At this point cwnd=40, FlightSize=0 (all ACKed).
+0 write(4, ..., 15000) = 15000

// sender sends all his data (10 seg)
+0 > . 20001:21001(1000) ack 1
+0 > . 21001:22001(1000) ack 1
+0 > . 22001:23001(1000) ack 1
+0 > . 23001:24001(1000) ack 1
+0 > . 24001:25001(1000) ack 1
+0 > . 25001:26001(1000) ack 1
+0 > . 26001:27001(1000) ack 1
+0 > . 27001:28001(1000) ack 1
+0 > . 28001:29001(1000) ack 1
+0 > . 29001:30001(1000) ack 1

// segment 20001:21001 is dropped
+.010 < . 1:1(0) ack 20001 win 65535 <nop,nop,sack 22001:30001>

+0 > . 30001:31001(1000) ack 1
+.010 < . 1:1(0) ack 20001 win 65535 <nop,nop,sack 22001:31001>

+0 > . 31001:32001(1000) ack 1
+.010 < . 1:1(0) ack 20001 win 65535 <nop,nop,sack 22001:32001>

+0 > . 32001:33001(1000) ack 1
+.010 < . 1:1(0) ack 20001 win 65535 <nop,nop,sack 22001:33001>
// 3 dupAck, enter PRR

// ASSERT FAST RETRANSMIT
// The kernel re-sends the exact segment that was officially declared lost. pipe = 8 && ssthresh = 20.
+0 > . 33001:34001(1000) ack 1
+0 > . 20001:21001(1000) ack 1

+.010 < . 1:1(0) ack 21001 win 65535 <nop,nop,sack 22001:34001>