[LARTC] How to calculate HTB quantum

[Radu CUGUT]

Hello all,


I have a question about the quantum parameter of a HTB class:

Is there a formula to calculate the quantum parameter of a class,
having the rate and ceil as parameters?


Sometimes, if I omit putting the quantum parameter for a class, I get
a message like "HTB: quantum of class ..... is big/small. Consider r2q
change" and shaping doesn't work very smooth sometimes. This is a
common warning and I saw on lartc mailinglist that there are multiple
ways to fix it.
But, I found a shaper script one on an linux box that had a formula
for calculating the quantum. I have no idea where the guy that wrote
that formula came up with it, but when I use it, it seems to work.
What I ask if someone can explain to me why?

The formula I found is this:

quantum = rate*8/5
if quantum>24000 then
   quantum = 24000
if quantum<1500
   quantum = 1500

on the root class, there is no r2q parameter set, so I guess HTB puts
the default value for it.

This works for me. But I don't like that I don't know why?



Thanks very much for any answer.





-- 
Radu Cugut