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Date: Fri, 04 Apr 2008 15:07:17 -0500
From: Wenji Wu <wenji@...l.gov>
To: Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
Cc: 'John Heffner' <johnwheffner@...il.com>,
Netdev <netdev@...r.kernel.org>
Subject: Re: RE: A Linux TCP SACK Question
> On Fri, 4 Apr 2008, Wenji Wu wrote:
>
> > Every system runs Linux 2.6.24.
>
> You should have reported kernel version right from the beginning. It
> may
> have a huge effect... ;-)
>
> > When sack is on, the throughput is around 180Mbps
> > When sack is off, the throughput is around 260Mbps
>
> Not a surprise, once some reordering is detected, SACK TCP switches
> away
> from FACK to something that's not what you'd expect (in 2.6.24), you
> should try 2.6.25-rcs first in which the non-FACK is very close to
> RFC3517.
>
> > I was thinking that if the reordered ACKs/SACKs cause cjavascript:parent.send('smtp')
Send Message
Sendonfusion in the
> > sender, and sender will unnecessarily reduce either the CWND or the
> > TCP_REORDERING threshold. I might need to take a serious look at the
>
> > SACK implementation.
>
> I'd suggest that you don't waste too much effort for 2.6.24. ...Most
> of it
> is recoded/updated since then.
Thanks, i would try it on the latest version and report the results.
wenji
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