RTO calculation (2)


Problem of the old calculation algorithm
According to Queuing theory, RTT delay is proportional to 1/(1-L) 
(where L = network load)
If network usage is 50%, RTT becomes twice as much.

New calculation algorithm 
            Err = measured RTT - SRTT
            SRTT = SRTT + g * Err    (g is usually set to 0.125)
            D = D + h * (|Err| - D)  (h is usually set to 0.25)
            RTO = SRTT + 4 * D

"D" represents smoothed Mean Deviation
Mean Deviation is good approximation to the Standard Deviation
Avoid to compute a square root.