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Date:      Fri, 11 Mar 2005 08:49:04 -0800
From:      Brooks Davis <>
To:        jim song <>
Subject:   Re: why my dummynet queue not work?
Message-ID:  <>
In-Reply-To: <>
References:  <> <> <>

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[Please don't top-post.]

On Fri, Mar 11, 2005 at 01:34:10PM +0800, jim song wrote:
> Brooks,
> Actually I use the freebsd box as an router. I set the tcp window in=20
> another two windows box running iperf (iperf -w 5M).

I'm pretty sure iperf only really sets the socket buffer size, not
the tcp window size.  In fact, that's what the help entry says:

  -w, --window    #[KM]    TCP window size (socket buffer size)
At least on FreeBSD the maximum window size is controlled by a global
variable.  You need to make sure you are setting both.  If you want to
use windows end-hosts, you'll need to ask a windows list what you need
to do there.

> Before I add in the pipes, the throughputs could reach 300M, but after
> I config in the two pipes(200M bandwidth, 25ms delay), the throughput
> degrade to about 5M.=20

That's expected.

> BTW, is there some limitations to tcp connections passing through a=20
> router?

No, dummynet doesn't know anything about TCP.

-- Brooks

> On Thu, 10 Mar 2005 20:39:33 -0800, Brooks Davis
> <> wrote:
> >=20
> > Why are you using the queue parameter at all?  If you just want to
> > emulate a pipe there is usually no need to do that.  Have you adjusted
> > your socket buffers in addition to your max TCP window size?
> >=20
> > -- Brooks
> >
Any statement of the form "X is the one, true Y" is FALSE.
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