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From: Sam Leffler <sam@errno.com>
Organization: Errno Consulting
To: Michal Mertl <mime@traveller.cz>, current@freebsd.org
Date: Thu, 30 Oct 2003 08:04:58 -0800
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Subject: Re: jumbograms (& em) & nfs a no go
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On Thursday 30 October 2003 04:46 am, Michal Mertl wrote:
> I wanted to test gigabit network performance and found out that current
> (from 5.0 to up to date -current) doesn't fully work with jumbograms (MTU
> set to 6000), Intel adapters and nfs (both UDP and TCP).
>
> I checked that the same thing works with 4.9.
>
> I then left one computer at 4.9 and upgraded the other to 5.0. When I
> mount a partition from 5.0 machine I found out, that copying reliably
> works only from 5.0 to 4.9. The other way around I see messages 'em0:
> discard oversize frame (ether type 800 flags 3 len 67582 > max 6014)' on
> 5.0 and the copying stalls. On 4.9 machine I later see 'nfs server
> 10.0.0.2:/usr: not responding'. The interface is stuck for some time - can
> be revived by changing mtu back to 1500 and down/up sequence.

I've ran many jumbogram tests of machines connected with a cross-over cable 
and em devices at each end.  If you've got a swtch in the middle make sure it 
does the right thing.

	Sam