TCP Round Trip Time and Timeout

EstimatedRTT = (1-x)*EstimatedRTT + x*SampleRTT

• Exponential weighted moving average

• influence of given sample decreases exponentially fast

• typical value of x: 0.1

Setting the timeout

• EstimtedRTT plus “safety margin”

• large variation in EstimatedRTT -> larger safety margin

Timeout = EstimatedRTT + 4*Deviation

Deviation = (1-x)*Deviation +

x*|SampleRTT-EstimatedRTT|

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