[132204] in North American Network Operators' Group
Re: mtu question
daemon@ATHENA.MIT.EDU (Mark Smith)
Wed Nov 17 16:48:24 2010
Date: Thu, 18 Nov 2010 08:18:10 +1030
From: Mark Smith <nanog@85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org>
To: Brandon Kim <brandon.kim@brandontek.com>
In-Reply-To: <BLU158-w6113843F4430EF815567C8DC380@phx.gbl>
Cc: nanog group <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Wed, 17 Nov 2010 16:23:54 -0500
Brandon Kim <brandon.kim@brandontek.com> wrote:
>
> Jack brings up a good point. MTU is basically pointless since packets never traverse any real interface.......
> So in theory the size can be anything...
>
>
Not quite. You hit packet length field limits. IPv4 packets can't be
larger than 65535, and IPv6 packets also can't be larger than 65 576
(40 byte IPv6 header + 2^16 payload), unless the jumbograms and the
jumbo payload extension header is supported. Last time I checked, by
setting the loopback MTU > 65 576, Linux, for example, doesn't support
the jumbo payload extension header (or if it does, I didn't spend
enough time finding out how to switch it on - a very large MTU didn't
trigger it).
That being said, with a 64K MTU on loopback, you can legitimately claim
to get >10Gbps at home, as long as you don't mention how you're doing
it ;-)
Regards,
Mark.
