Smooth Round-Trip Timer (SRTT) - This is the average time that it takes to send and receive packets from a neighbor. This timer is used to determine the retransmit interval (RTO).

• 平顺往返计时器(SRTT)-这是传送并接收来自一个邻居的封包，平均所花费的时间。这只计时器用来决定重送间隔(RTO)。