[e2e] An alternative algorithm of calculating RTO
touch at ISI.EDU
Mon Jun 3 14:40:02 PDT 2002
jaglee at peoplemail.com.cn wrote:
> The algorithm in a nutshell:
> (1) Calculate mean measured round-trip time and measured round-trip time variation: Suppose mrtt, mrtt, ..., mrtt[N-1] are the measured round trip time of the N most recently acknowledged packets without re-sending,
> let mmrtt <- (mrtt + mrtt + ... + mrtt[N-1]) / N;
> mrttvar <- (abs(mrtt - mmrtt) + abs(mrtt - mmrtt) + ... + abs(mrtt[N-1) - mmrtt) / N;
This is known as a "rolling average" and "rolling variance", and have
been tried in a number of contexts before, in particular, for a ECG
"An Experimental ECG Scanning System," (extended abstract)
K.P. Birman and J.D. Touch, Proc. Of the Ninth Annual Conf. Of the IEEE
Engineering in Medicine and Biology, Boston, Nov. 13-16, 1987. The note
on which this extended abstract is based is available at
The use of 'calibrating factors' was used in that work to describe the
difference between signal and noise - literally, signal was when the
data exceeded the average by more than some multiple of the variance.
It has been raised as an alternative to TCP's capacitive decay model
several times, notably at several IETF TCPIMPL meetings. Whether it is
strictly more stable or useful than the current 'capacitative decay'
model has not yet been proven.
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