Re: [LARTC] Best way to limit the rate

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

On Friday 29 November 2002 14:10, Mathieu Deziel wrote:
> Suppose you need to limit the rate of the traffic that flows in an HTB
> leaf class to 32kbits/sec
>
> I can think of three ways to do it:
>
> 1.
> make rate = ceil = 32kbit when creating this HTB leaf class.  A pfifo
> qdisc can then be attached to this HTB leaf class to reduce the queue
> size, and therefore reduce the latency of the packets.
>
> 2.
> Attach a TBF qdisc to this HTB leaf class, and configure it properly.
HTB _is_ TBF.  So the first idea is better.  A ceiled htb class = tbf qdisc.

> 3.
> Have a policing filter before the HTB leaf class that will limit the
> rate of the traffic before it enters the HTB leaf class.
>
> Which one of these methods is the best?
> My tests have shown that the latency of the packets is dramatically
> better with method 3.  Anybody has an idea why this is the case?
Solution 3 has the advantage that you limit the packet at a rate, but you 
don't have a queue.  The policer uses a small tbf queue to limit the packets.  
The packets are simply dropped if they exceed a certain rate.  It's also not 
possible to share bandwidth like you can do with cbq/htb.

Stef


-- 

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