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To: Julian Elischer <julian@elischer.org>
From: Mike Karels <karels@karels.net>
In-reply-to: Your message of Sat, 15 Sep 2007 10:40:57 -0700.
	<46EC1929.5020706@elischer.org> 
Date: Sat, 15 Sep 2007 13:50:00 -0500
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Cc: FreeBSD Net <freebsd-net@freebsd.org>,
	David Christensen <davidch@broadcom.com>, Jack Vogel <jfvogel@gmail.com>
Subject: Re: BCE on FreeBSD and oversized packet acceptance. 
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> > Secure Computing (my employer) has a modification that seems reasonable
> > to me (well, I guess I wouldn't have done it otherwise).  We adopted the
> > existing but unused JUMBO_MTU capability flag, and, if enabled, instructs
> > the driver to receive jumbo frames according to the hardware limits.  With
> > that flag, the MTU may be 1500, but the driver is still instructed to
> > receive jumbo frames even without sending them.  The reason for this
> > is the lack of a way to negotiate the use of jumbo frames per host
> > (as far as I know; such a thing would certainly be useful, though).

> certainly the adoption of that flag is reasonable.
> is it settable from ifconfig?
> it's probably better than saying "enable jumbo reception 
> if mtu is greater than 1600 bytes" or whatever.. 

Yes, the flag is settable with ifconfig.  It expands the "accept
what is convenient" to "and also accept whatever is reasonable
for jumbo" (for this NIC).

		Mike