Smoothed Round Trip Time

We mentioned in other tutorials that TCP uses a timer to decide when to retransmit the data. The question we should ask is 'how long should TCP wait before retransmitting?'. In more professional jargon the retransmission timer is referred to as RTO (retransmission timeout). To compute the current RTO, TCP sample the round trip time to compute a smoothed round-trip time.

RFC 2988 explains in details the algorithm behind RTO computing

The smoothed sound trip time video explains the algorithm