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From: Giorgos Keramidas <keramida@freebsd.org>
To: perryh@pluto.rain.com
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Date: Wed, 30 Jul 2008 07:36:34 +0300
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	(perryh@pluto.rain.com's message of "Tue, 29 Jul 2008 21:04:53 -0700")
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Cc: freebsd-questions@freebsd.org
Subject: Re: setting the other end's TCP segment size
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On Tue, 29 Jul 2008 21:04:53 -0700, perryh@pluto.rain.com wrote:
>> [TCP] splits traffic to 'segments' using its own logic ...
>
> Is there a simple way for a FreeBSD system to cause its peer
> to use a transmit segment size of, say, 640 bytes -- so that
> the peer will never try to send a packet larger than that?
>
> I'm trying to get around a network packet-size problem.  In
> case it matters, the other end is SunOS 4.1.1 on a sun3, and
> I've been unable to find a way to limit its packet size
> directly.

Setting the interface MTU should do it, i.e.:

    ifconfig re0 mtu 640

Not all interfaces support setting the MTU and some may have
range restrictions though.