Re: [LARTC] HTB classes: is it true that the rate of a parent MUST be exactly equal to the sum of ra

[Stef Coene <stef.coene@docum.org>]

On Sunday 18 May 2003 19:27, Martin A. Brown wrote:
> Miernik,
>
> I'll add a bit to Stef's answer.
:)

>  : When configuring HTB classes, is it true that the rate of a parent
>  : MUST be exactly equal to the sum of rates of it's children?
>
> No.  This is not true.  This is merely a recommendation for how to use
> HTB.  When the parent class ceil matches the total of all of the ceil
> parameters of the children classes, there is no way for bandwidth usage to
> exceed the parent ceil.
It's not the "total of all of the ceil", it's the maximum of all the ceil 
parameters of the children classes.
And you can exceed the parent ceil.  See me other post on this subject.  It 
can because the rate of a class is the minimum the class always gets.  Even 
if it exceeds the parent ceil.

>  : For example let's say I have a 160Kbit link, and two clients. I want
>  : each of them to have equal transfer rate, and ceil each of them to
>  : 70Kbit. I leave 5% of the link idle as suggested on
>  : http://www.docum.org/stef.coene/qos/faq/cache/9.html
>
> I have a clarification to make, which may help you understand all of the
> answers to your questions:
>
>    With HTB, shaping is only performed by the leaf class.  Why
>    bother setting rate and ceil in parent classes?  The ceil is
>    used by the parent class to lend bandwidth to the child
>    classes [1].  In short, all non-leaf classes use ceil to cap how
>    much bandwidth to lend to a child class.
This is true for the ceil.  But not for the rate.  The rate of the parent 
class is used to split the traffic.  See other post on the same subject for 
an example.  And I just realized that I stated before that the parent rate is 
never respected.  That's not true.  It is.  But I don't know how exactly.

> I would disagree with Stef (note, Stef *does* have more experience with
> HTB, so let's see what he says).  These setups are not equivalent.
Thx ;)

> Miernik--I would recommend this type of approach.  In your example,
> though, you are using a rate which is below Devik's recommend minimum rate
> for reliable operation of HTB [2].  Perhaps you could create 25 classes,
> and put two IPs in each class.  That gives you a 6kbit rate for each child
> class.
I think Devik means that this is a minimu rate for active classes.  And he 
states that there are only some of the classes active.  So the real rate will 
always > 6kbit.  As long as quantum is big enough, I don't think there will 
be a problem.

I deleted some parts of Martins answer.  My conclustion : I need to do some 
more tests to find out how the parent settings influence the children.

Stef

-- 

stef.coene@docum.org
 "Using Linux as bandwidth manager"
     http://www.docum.org/
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