[PLUG] Bit-Torrent

[Galen Seitz]

Charlie Schluting <charlie at schluting.com> wrote:

> On 2/4/2005 7:37 AM, Galen Seitz wrote:
> > I wonder whether this can really be blamed on the DSL hardware.  I think
> > poor throughput in the un-traffic-shaped case may be due to high TCP ACK
> > latency.  It seems that this would be likely to happen with any TCP
> > connection with large buffers and a slow (relative to ethernet) bit
> > rate.  In this case, getting the TCP ACK packets sent in a timely manner
> > is certainly a software issue.
> > An interesting experiment would be two simultaneous UDP transfers.
> > Since UDP packets aren't ack'd, this should show whether the hardware
> > slows down when both directions are utilized.
> 
> 
> Yes, this is likely the cause.
> FreeBSD's ipfw has a way to prioritize ACKs that have little ot no
> payload, and this helps tremendously on cable. (of course, pf+altq can
> do it too)
> 
> I don't know if linux can do the same ... but its much better than
> throttling bandwidth all together!
> 

Assuming it's correct, there is a fairly detailed explanation of
what is happening in this HOWTO:
  http://tldp.org/HOWTO/ADSL-Bandwidth-Management-HOWTO/index.html

galen