Re: [LARTC] How HTB treats priorities?

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

On Saturday 04 January 2003 21:21, ISC Robert Krycza³o wrote:
> Hello Stef,
Hi,

I have 1 big remark.  You results are incorrect and not usable.  The quantum 
of your class is too low.  You have a rate of 1kbit, so quantum is 1kbit / 10 
= 100 bit.  In your case, quantum is important.  Each class may send quantum 
bytes to use all remaining bandwidth from the parent.  Let's say class 21 and 
22 are fighting for bandwidth.  The qauntums are 400 and 300.  So class 21 
may send 400bit and after that class 22 may send 300bit.  But most packets 
are 1500byte !!!   So 1500 byte is sended.  So the internal calulations of 
htb are totally fucked up (sorry for the language :).

If you want to get some good results, use at minimum a rate of 15kbit or 
change the r2q parameter.  If you are curious about the qauntum parameter, I 
have some more info on www.docum.org on the faq page.

I redid some of your test with higher rates.  I multiplied the rates with 16 
(so kbit -> kpbs and x2).  And I added r2q = 1 so lowest quantum is 
2000bytes.

And I toke a wrong conclusion.  The parent ceil is not respected IF the sum of 
the rates of childs exceed the parent ceil.  So if you have 2 childs classes 
with rate = 100 and a parent ceil of 100, the parent ceil is not respected 
and the childs will get each 100.  But if you have 2 class with rate = 2 and 
parent ceil = 100, then the childs to gether will never get more then 100.  
So the parent ceil is respected.

Traffic in class 21 : 127.5 KB/s
Traffic in class 22 : 256.1 KB/s
Traffic in class 21 and 22 : 120.4 KB/s and 137.7 KB/s
	so the parent ceil is respected.  But I still don't know how the traffic is 
divided.  The sum is 258.1 so class 21 gets 46.6%.  I think each class gets 
the configured rate and the remaining traffic is splitted 50-50.

> During the tests I discovered that in case of root class (1:0 in my
> example) only rate matters not ceil. I accidentally changed 1:2 and 1:3 to
> root classes and then 22,23,24 were limited to 8kbit/s.
I did the same.  And indeed.  For a root class, ceil = rate even if you 
specify a higher ceil.  Strange.  On the other hand, it's logic to create 1 
root class that holds all traffic so it has rate = ceil.  It's the 
"bottleneck" within the htb structure.

Stef

-- 

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

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