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Date:	Wed, 09 Apr 2014 14:41:05 -0700
From:	Eric Dumazet <>
To:	Francois WELLENREITER <>
Subject: Re: Does IPv6 support Jumbograms ?

On Wed, 2014-04-09 at 21:42 +0200, Francois WELLENREITER wrote:
> Hi there,
> I've been recently running performance tests with the loopback interface
> increasing the MTU over the 65535 byte limit.
> I was really surprised to see that a simple scp onto the ::1 address
> systematically blocked after transferring about 2,4 MB.
> My interpretation of this behavior is that the current IPv6 kernel layer
> does not support Jumbograms at all. Am I wrong ?
> If that's not the case, what could then the right interpretation of this
> issue ?
> And whenever I'm right, is there any plan to support this feature in a
> near future ?

What do you mean by blocked ?

Please give more details (kernel version, exact mtu...), because it
should not happen !

# ifconfig lo mtu 100000
# scp -6 vmlinux edumazet@...-localhost:/tmp
100%   24MB  23.5MB/s   00:00    
# ls -l /tmp/vmlinux
-rwxr-xr-x 1 edumazet eng 24668915 Apr  9 14:37 /tmp/vmlinux

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