Date: Wed, 30 Sep 2009 14:22:33 +0800 From: Eugene Grosbein <eugen@kuzbass.ru> To: Brett Glass <brett@lariat.net> Cc: net@freebsd.org Subject: Re: ipfw gred parameters Message-ID: <20090930062233.GA28758@svzserv.kemerovo.su> In-Reply-To: <200909291855.MAA21423@lariat.net> References: <200909291855.MAA21423@lariat.net>
next in thread | previous in thread | raw e-mail | index | archive | help
On Tue, Sep 29, 2009 at 12:54:53PM -0600, Brett Glass wrote:
> I've been trying to determine the best parameters for gred ("gentle
> RED") to allow graceful bandwidth limiting in ipfw, but have found
> precious little guidance on the Web as to what the parameters mean.
> The code gives some hints, but I'm still uncertain: what parameters
> work best in a typical system? And how do the parameters submitted
> to "dummynet" correspond to the ones usually seen in descriptions
> of the algorithm?
I use the following schema:
ipfw add pipe $pipeno config bw ${group_bw}Kbit/s queue $qslots \
gred $w_q/$q_min/$q_max/$max_p
pipeno: number of pipe
group_bw: total pipe bandwidth
qslots: length of GRED queue
w_q: constantly equals to 0.002 (0 < w_q < 1),
exponential factor
max_p: constantly equals to 0.1, the probability of packet
drop lineary grows from zero upto $max_p
while GRED queue occupancy grows upto $q_min.
q_min: see max_p
q_max the probability of packet drop lineary
grows from max_p to 1 while GRED queue occupancy grows
from q_min to q_max
I choose q_min = 0.9*qslots, q_max = qslots.
For narrow pipes qslots should be small if short ping delays
are more preferable, e.g. qslots=50 for 256Kbit/s
or qslots=30 for 64Kbit/s.
For large bandwidth it's suitable to increase qslots;
for example, I use qslots=1000 for 10-15Mbit/s.
Eugene Grosbein
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20090930062233.GA28758>