[BitTorrent] Re: IP_TOS setting wrong (patch)

Gregory P. Smith gpsmith at gmail.com
Wed Dec 22 19:51:19 EST 2004

> > Its diffserv "IPTOS_PREC_PRIORITY 0x20"
> >
> > A more appropriate value would be "IPTOS_THROUGHPUT 0x08"
> >
> The value TOS value of 32 equates to the DSCP value of 8, which is used
> by the scavenger service.  Instead of indicating that throughput matters
> more than latency for this application, it indicates that the traffic is
> low priority, but can consume much bandwidth, and thus should be
> throttled unless there is "excess" capacity.  For example, at work I am
> At least, that's my take on it.  See http://qbone.internet2.edu/qbss/
> for general info on the scavenger service and
> http://www.aarnet.edu.au/engineering/networkdesign/qos/ for details on
> the history and use of these fields ("Precedence and DSCP" and "Using
> the Scavenger service").
> Be advised that the default queuing disciplines in linux respect the old
> RFC 791 TOS values IPTOS_THROUGHPUT and IPTOS_LOWDELAY and do not make
> use of newer DSCP values.

IPTOS_THROUGHPUT is a much more traditional value than any of the new
fangled DSCP stuff.  regardless the tos value is configurable in 3.9.0
and defaults to the more traditional value that most everything else
uses for bulk traffic (ftp clients and servers, ssh/scp/sftp, etc).

a great description of the other settings IP_TOS bit settings can be found here:


as "200 bald men fighting over six combs"

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