RTO calculation (2)
- Problem of the old calculation algorithm
- RTT fluctuates widely in large scale networks.
- Since old algorithm uses "Average", it can't keep up with fluctuation.
- 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
- Based on "Deviation"
- "D" represents smoothed Mean Deviation
- Mean Deviation is good approximation of the Standard Deviation
- By using Mean Deviation, we can avoid computing square root.