Re: [LARTC] Making tcp start transfers slow

[Andy Furniss <andy.furniss@dsl.pipex.com>]

Roy wrote:
> I just had one idea, about this.
> 
> what if  make iptables module which will make something like enlarged copy
> of syn packet and send it back to the sender?
> (another option would be to kill 1 or 2 ack packets for one syn packet this
> whould force server to reduce speed)
> 
> 
> that way htb could count upcoming packet and prepare by reducing other
> connetions speed?
> of course that synthetic packet will have higest possible priority since it
> supposed to be appear in future so  cant be shaped anyway
> 

I don't really get this :-)


> 
> I will try to add this functionality to my imq module next week probably.
> ------------------------
> connbytes solution is not good for this, it slows down small picture loading
> in web pages very much, and big downloads get even more "unused" bandwitch.
> so effect is not good. expecialy that looks bad on network, when pages
> become incredibly slow, but big downloads fast.

Depends on lots of things I suppose - the way I have it set new 
connections get 256kbit - not that bad for browsing. ISTR seeing one of 
your scripts that did similar, IIRC using sfq with low rates. I don't 
quite do it like that - for a start sfq 128 queue length is too much and 
if you use it on ingress sfq will hash the ~4 simoultaneous connections 
your browser makes into one slot. I guess yours simulated a drop with 
the reordering when they swapped queues rather than really dropping with 
a short queue to get out of slowstart.

SFQ causes instability every time it rehashes on ingress because of this 
- there is a todo in the code somewhere. I like to set perturb high.

This ingress shaping with stuff made for egress is a bit tricky - but it 
can be tweaked a bit.

Andy.



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