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Date: Wed, 8 Sep 2004 21:44:53 +0100
From: David Malone <dwmalone@maths.tcd.ie>
To: Soo-Hyun Choi <shchoi@gmail.com>
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cc: freebsd-hackers@freebsd.org
Subject: Re: TCP RTO
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On Wed, Sep 08, 2004 at 05:43:36PM +0100, Soo-Hyun Choi wrote:
> These variables are used to calculate the TCP RTO. But why do they
> have the two different version of variables?

There are two different variables because they store different
things. One measures the average of the round trip time and the
other measured the variability of the round trip time. The RTO is
calculated as the average plus some constant times the variability.

> The interesting thing is
> the 't_' variables are a fixed-point integer, and the original
> variables are just floating-point values. I assume the reason why they
> have is to avoid the floating-point arithmetic in the kernel. Is this
> really only reason for being two different version of those?

The calculation is designed to be done with fixed point calculations,
but this is not why there are two variables.

	David.