[ih] TCP RTT Estimator

[touch at strayalpha.com]

> On Mar 11, 2025, at 11:07 AM, Michael Greenwald via Internet-history <internet-history at elists.isoc.org> wrote:
> 
> If I am remembering correctly (I'm on the move, and don't have access to anything other than email to checkup anything at the moment), the RTT estimator is not exactly the standard algorithm for computing moving average. I think it separately estimated RTT average and RTT variance, and added the 2 together (which meant the estimate actually increased, briefly, if the RTT was dropping rapidly.)
> Also, wasn't there some variation (Craig and MRose? or Van? or Lixia?) to eliminate individual round-trips that may have been computed by a duplicate or missing packet?

It’s an inverse exponential decay, similar to how a capacitor discharges over time. Each time measurement contributes (exponentially) less over time.

A true moving average typically as a finite window and computes a mean over that window, in which each element counts the same until it doesn’t count at all.

Joe

—
Dr. Joe Touch, temporal epistemologist
www.strayalpha.com