[adsl-qos] BitTorrent Woes

[Dan Singletary]

The number of open connections does not make a difference.  Also, 
dsl_qos_queue is not tcp-session-aware.. so you can have as many as you 
want and it wont divide bandwidth depending on the number of sessions. 
dsl_qos_queue only divides bandwidth based on fwmark, using a priority 
queuing mechanism that will always empty the highest priority bucket, 
although will occasionally send a packet from every bucket (To prevent 
total starvation of a lower priority band by a higher).

-Dan

Frank Luithle wrote:

> On Saturday 20 March 2004 00:57, Daniel Brown wrote:
> 
> 
>>I've recently installed dsl_qos_queue to try and solve out perennial
>>problem here of the entire internet connection speed slowing down to
>>the speed of cold treacle whenever a BitTorrent is active, or someone
>>is using the Direct Connect service. It's done a fairly good job, but
>>there are still massive slow-downs occasionally. I've tentatively
>>concluded that the slow down is because of the many TCP connections
>>these two protocols open for even just one download. I would like to
> 
> 
> I'm using BT a lot, too, and I've had the exact same thought, but I don't 
> think the number of simultaneously open connections makes any difference.
> 
> What counts in the end is the amount of data leaving your interface, and 
> that proper accounting is done by the queuing device (dsl_qos_queue does 
> that).
> 
> I'm not even using dsl_qos at the moment and I only start to get into 
> trouble when the upstream is saturated (usually mostly always the case 
> with BT) and the peers start sending me data really fast.  But this is 
> just an instantiation of the usual problem that too many small (ie. ACK) 
> packets are generated and the huge overhead generated by them *on the 
> modem line* makes your queue overflow.
> 
> 
>>specify a list or range of ports to squish into, say 15kB/s of
>>bandwidth, leaving some for other services. My theory is that at the
>>moment, dsl_qos_queue is detecting each TCP connection as wanting an
>>equal share of the upstram bandwidth, and because there are so many of
>>the blighters, they just guzzle up nearly all of the bandwidth.
> 
> 
> dsl_qos filters into one of six predefined classes by examining the 
> fw_mark (a number assigned to the packet by iptables, the firewall).
> 
> So what you have to do is make sure that all packets to and from BT 
> clients are going into one class.  You will have to filter ports 6880 
> through 6889, both destination and origin, which will catch almost all of 
> BT traffic (some peers might have a non-standard configuration that is 
> using an entirely different port, but from several netstat lookups I've 
> done on my machine I've learned that this is very rare).
> 
> Mark all packets from/to these ports with a "6", maybe add the 'Direct 
> Connect' traffic also and you will be fine.  Don't use the mark "6" for 
> other traffic.
> 
> Always recall that if your upstream rate becomes to small, BT download 
> rates go down to almost zero in no time (I've found that anything below 
> 7-8 kB/s leads to really bad download rates).
> 
> Again:  I don't think the number of open connections does make a 
> difference here.
> 
> --Sigi