when the congestion window on the sender is growing, it effectively doubles the number of packets in flight during the time it takes to send a packet and receive the acknowledgment back.
当发送方的拥塞窗口增大时,它会在发送出一个包和收到应答之间的时间内成倍地增加传输中的包的数目。
during the slow-start stage, the congestion window of tcpw is based on exponential growth mode, which will cause the datagram increases too fast and prompt the probability of congestion.