TCP/IP 详解 卷1 ch21 TCP的超时与重传

1. TCP超时与重传

指数避让（exponential backoff）

2. Round-Trip Time Measurement
R <- aR + (1-a)M    a = 0.9

RTO ： Retransmission Timeout
RTO = Rb                b = 2

3. TCP的4个定时器

1） A retransmission timer is used when expecting an acknowledgment from the other end. 重传定时器
2） A persist timer keeps window size information flowing even if the other end closes its receive window.
3） A keepalive timer detects when the other end on an otherwise idle connection crashes or reboots. 保活定时器
4） A 2MSL timer measures the time a connection has been in the TIME_WAIT state.