Re: [LARTC] Is this possible?

[Andreas Klauer <Andreas.Klauer@metamorpher.de>]

On Thu, Feb 23, 2006 at 06:38:09PM +1000, Russell Stuart wrote:
> For example, lets say we have a 1000kbit link, and two
> classes sharing that link:
> 
>   - Voip - ie high prio real time, and
>   - Web - background traffic.

Have you measured this link, i.e. when there is no activity 
and you start some Voip sessions, do they get a constant 
downstream of 1000kbit?

It may very well be that you have to measure the real throughput 
and then go a little lower (since you have to be the bottleneck), 
however having to throw 30% of bandwidth away sounds a bit too 
harsh to me.

>             Guaranteed Rate    Ceiling    Prio
>   Link       700kbit           700kbit
>    |--Voip   200kbit           700kbit     1
>    \--Web    300kbit           700kbit     2

Are there other classes as well, because the sum of Voip + Web rate 
is just 500kbit, where the parent class offers 700kbit? You should 
make sure that the sum of child class rates equals the parent class 
rate. HTB results get more predictable that way.
 
> To be more precise, I want to create some "headroom" that
> VOIP can use, but Web traffic can't.

Usually, this "headroom" is the rate. In your example, Voip has 
200kbit of bandwidth guaranteed. Web traffic can't use it unless 
of course there is no Voip traffic at all.

Another way of indirect headroom would be to hard limit the Web class, 
i.e. give the Web class a lower ceil than the other classes. This way, 
there is bandwidth that the Web class can't use no matter what, even 
if the link is completely empty.

Regards
Andreas Klauer
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