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From: Don Bowman <don@sandvine.com>
To: "'Peter J. Blok'" <pblok@inter.NL.net>, freebsd-net@freebsd.org
Date: Thu, 9 Oct 2003 11:02:39 -0400 
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Subject: RE: Giga-bit switches
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From: Peter J. Blok [mailto:pblok@inter.NL.net]
> Hi,
> 
> This is just a warning. I am setting up a Giga-bit network 
> trying to use Jumbo 
> frames. For NIC the ability to do larger frames is usually 
> listed, but that 
> doesn't seem to be the case for switches.
> 
> I have bought a Netgear GS104 switch, which does list a 
> buffer per port of 
> 12K. However, according to Netgear support, it is not 
> supported and working. 
> They just say that there is no mentioning of Jumbo frame 
> support, therefore 
> it is not supported. Even on the more expensive Netgear 
> switches it is not 
> listed, so it is trial-on-error policy.
> 
> My understanding is that the Giga-bit definition includes 
> large frame support 
> and if you claim to have a Giga-bit switch you should support 
> large frames, 
> unless specifically excluded.

jumbo frames are not part of the standard, and are in
general poorly supported. For some cisco devices, they
do 'mini giants', e.g. ~1600 mtu. Other cisco devices
will support 9K frames, but @ the expensive of lowering
the overall buffering (all frames are assumed to be 9K
now, so ~1/4 of the packets may be buffered).

for cisco devices, the support will be on a line card
by linecard basis.