Re: [LARTC] htb3 & imq

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

> i have acheived restrictinng both in&out trafic using imq0.. i have
> marked the packets on different ineterface, hence sending them to the
> rules i want & then used **FORWARD** to imq .!.. it works pretty good,
> though done in a test bed of 4 ip.. i want to scale it to our running
> linux box handling about 250 ip's with 1.5mbps link..
> the question now i have start thinking, after Tobias Geiger'smail is -->
> what will be the cpu overhead when the linix box also runs squid in it..
>   withh htb3 & imq show the same result as shown in the test ?
> i hope & feel it will .. :)
I think the CPU is not so important.  I think there are other problems with 
shaping incoming bandwidth with imq.  First of all, you can create an extra 
queue and so extra delays.  But using a "shared" structure to manage incoming 
problems can also be a problem.  Imagine a setup where 100 kbps is split in 2 
parts of 50 and they can borrow from each other.  One class is empty and one 
class is filled.  When there is suddenly a burst in the empty class of 50 
kbps, it will take some time before the traffic in the full class will 
throttle down to 50kbps.  And don't forget the extra delay introduced by the 
imq device, so the response will even be slower.  It's better to be sure the 
50kbps is available for the bursty traffic.  Of cours, you waste some 
bandwidth, but a few kbps is enough to make telnet more responsive.
So you can do some shaping on incoming traffic, but bursty traffic is not so 
easy to mange.

To be honest, I just start reading and thinking about shaping incoming 
traffic, so any suggestions are welcome.

Stef
 
-- 

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