Re: [LARTC] HTB: quantum vs. burst

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

On Thursday 16 January 2003 20:48, Pavel Mores wrote:
> On Thu, Jan 16, 2003 at 08:05:24PM +0100, Stef Coene wrote:
> > No.  I did some tests my self witb burst and cburst.  The problem is that
> > it's very difficult to measuer and explain it.  You have to believe Devik
> > that it works :)
>
> I'm not saying that I don't believe him. ;)  However, bursting within
> complex multilevel hierarchies can bring about a number of rather opaque
> interactions.  If you need to be able to understand this (in other
> words, to know what you are doing), the basic info from the docs is just
> not enough.

> > It also helps if you disable HTB_HYSTERESIS in the htb qdisc.  See faq
> > page for more info.
>
> Take a look at the 1:76's graph if you care - see that depression
> between 140.  and 170. second?  It's not there because of lack of demand
> - 1:77 is still asking for bandwidth.  It's probably 1:76 retaliating
> for being pushed above its ceil between 10. and 40. second.  If I
> understand the docs correctly, the depression should not be there since
> I *did* set 1:76's burst, too.  I was thinking about disabling
> HTB_HYSTERESIS in hope that doing so would remove this problem but I
> haven't tried it yet.
If you want to undestand what's going on, you also have to graph the tokens 
and ctokens.  I use the ethloop from Devik.  It's a very nice think ones you 
understand how it works.  I can send you my scripts and config files if you 
are intersed (and I think you are :)

> > No.  If you have a 10kbyte/s link and you have a class with ceil = rate > > 5kbyte/s and a big burst/cburst (100.000byte or so), you can measure the
> > burst.  The first 100.000 byte will be sended by the burst so it will be
> > sended in 10 second.
>
> I just repeated the experiment with the exception that only 1:78 (the
> one with burst set) was asking for bandwidth (the competing 1:77 was
> silent) and I'm afraid that I'm not able to see any burst anyway.  In my
> view, burst won't let me break my ceil. However, cburst will.
Indeed.  I think I need some sleep :)  Indeed, the ceil is respected if you 
use the burst parameter.  It's the parent ceil that's broken.

> > I have some very detailed information about how the burst and cburst from
> > parent and child classes are interacting, but I still have to create a
> > page for it.  It also explains how burst and cburst can exists and how
> > the tokens and ctokens are changing when you are using the burst.  Maybe
> > something I can do tonight.  I will keep you informed.
>
> That would be *great*. :-)
I had a hard time finding the directory where I stored my files :)
But I found it.  Now I have to figure out what I wanted to document :)

Stef

-- 

stef.coene@docum.org
 "Using Linux as bandwidth manager"
     http://www.docum.org/
     #lartc @ irc.oftc.net

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