LastByteSent - LastByteAcked = min{cwnd, rwnd}
cwnd++
,即每经过一个 RTT,总的 cwnd 就加倍。ssthresh = 2^16 = 65535 byte
。当超过这个值的时,每收到一个ACK:cwnd += 1/cwnd
,所以总 cwnd 增加 1,这样就变成了线性增加。ssthresh = cwnd/2, cwnd = 1
。cwnd = cwnd/2, ssthresh = cwnd
;然后每返回一个包:cwnd++
。