- #1
alman9898
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Homework Statement
For a given TCP connection, suppose 4 acknowledgments have been returned with RTTs: SampleRTT(4), SampleRTT(3), SampleRTT(2), SampleRTT(1). SampleRTT(1) is the most recent, SampleRTT(2) is the second most recent, etc.
Calculate EstimatedRTT...
Homework Equations
Initialize EstimatedRTT to SampleRTT(4), the first sample.
EstimatedRTT = [tex](1-\alpha)\times EstimatedRTT[/tex] + [tex]\alpha\times SampleRTT[/tex]
The Attempt at a Solution
Plugging in I get...
[tex](1-\alpha)^{3}\times SampleRTT(4) + \alpha\times(1-\alpha)^{2}\times SampleRTT(3) + \alpha\times(1-\alpha)\times SampleRTT(2) + \alpha\times SampleRTT(1)[/tex]
But, EWMA is supposed to put less emphasis on older values...this seems to work for SampleRTT(3) and SampleRTT(2) but SampleRTT(4) will have a larger coefficient. I believe it's supposed to be multiplied by a factor of alpha as well, but I can't seem to find any arithmetic error and it's very annoying...am I doing it wrong or what?
For reference, alpha = .1 in this problem, but that's not exactly important, the calculations should be the same.