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Date:      Mon, 7 May 2001 15:38:02 -0600
From:      "Kenneth D. Merry" <ken@kdm.org>
To:        Bob Willcox <bob@immure.com>
Cc:        hackers list <freebsd-hackers@FreeBSD.ORG>
Subject:   Re: Realy LARGE TCP/IP Window Size?
Message-ID:  <20010507153802.A2669@panzer.kdm.org>
In-Reply-To: <20010507162005.C55671@luke.immure.com>; from bob@immure.com on Mon, May 07, 2001 at 04:20:05PM -0500
References:  <20010507162005.C55671@luke.immure.com>

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On Mon, May 07, 2001 at 16:20:05 -0500, Bob Willcox wrote:
> 
> I am working on a FreeBSD device driver for my Co's GSN adapter and need
> to be able to set my TCP/IP window size to 512KB (or perhaps more). I
> have tried doing this with sysctl:
> 
> root@sebulba:p0 /root> sysctl -w net.inet.tcp.recvspace=524288
> net.inet.tcp.recvspace: 131072 -> 524288
> root@sebulba:p0 /root> sysctl -w net.inet.tcp.sendspace=524288
> net.inet.tcp.sendspace: 131072 -> 524288
> 
> and although the sysctl happily takes the specification, when I attempt
> an ftp command I get:
> 
> root@sebulba:p0 /root> ftp 192.168.1.2
> ftp: socket: No buffer space available
> 
> This is on a FreeBSD 4.0-stable system:
> 
> FreeBSD sebulba.vieo.com 4.0-STABLE FreeBSD 4.0-STABLE #202: Mon May  7 15:09:46 CDT 2001     bob@sebulba.vieo.com:/usr/src/sys/compile/GPXTEST  i386
> 
> Anybody have any ideas what I need to do to get this to work?

sysctl -w net.inet.tcp.rfc1323=1

You need that to be able to set your window size to anything over 64K.  I
think there's an rc.conf knob to do that so you don't have to tweak it
manually every time.

You really don't want to use ftp to test bandwidth.  Use netperf instead.
It is located in ports/benchmarks.

You might also be interested in the zero copy patches.  See:

http://people.FreeBSD.org/~ken/zero_copy/

The latest patches aren't linked off the page, they're available here:

http://people.FreeBSD.org/~ken/zero_copy/zero_copy.diffs.20010124

Ken
-- 
Kenneth Merry
ken@kdm.org

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