That is one of the problems here - in the RFC such problems do not arise, but the implementation needs
to address these correctly.
The RFC's solution to this problem, which involves t_gran, EXACTLY addresses this
| Your token bucket math, incidentally, is wrong. The easiest way to see this
| is to note that, according to your math, ANY token bucket filter attempting to
| limit the average output rate would have to have n = 0, making TBFs useless.
| The critical error is in assuming that a TBF allows "s * (n + R * rho)" bytes
| to be sent in a period R. This is not right; a TBF allows a maximum of s * R
| * rho per longer-term period R; that's the point. A token bucket filter
| allows only SHORT-term bursts to compensate for earlier slow periods. Which
| is exactly what we need.
Please take another look. The formula is correct (you will find the same one e.g in Andrew
Tanenbaum's book).
So I assume what you are referring to is the clause "average rate OVER ONE
RTT"? Sorry I missed that. I missed it because it is not TFRC's goal. Can
you point to the section in RFC3448 or RFC4342 that prohibits a TFRC sender
from ever sending a (transient) rate more than X over one RTT? RFC3448 4.6
allows burstiness much more than a single packet, and the intro allows
fluctuations of up to a factor of 2 relative to the fair rate
I think (with regard to the paragraph below) that your perspective is an entirely different one,
namely to solve the question "which kind of token bucket do we need to obtain an a rate which
is on average consistent with X".
That is *TFRC's* perspective: finding packet sends that on average are
consistent with X. As demonstrated by 4.6 and elsewhere
How much above X may an application transiently send? The intro would argue 2x.
But until this is truly resolved I want this patch in.
Fine, I disagree, Ian disagrees (as far as I read its messages). You are
fixing one problem and creating another: artificially low send rates
Eddie
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