[111291] in North American Network Operators' Group
Re: can I ask mtu question
daemon@ATHENA.MIT.EDU (Sam Stickland)
Tue Feb 3 07:04:28 2009
Date: Tue, 03 Feb 2009 12:04:22 +0000
From: Sam Stickland <sam_mailinglists@spacething.org>
To: Ricky Beam <jfbeam@gmail.com>
In-Reply-To: <op.uolf6zfjtfhldh@rbeam.xactional.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces@nanog.org
Ricky Beam wrote:
> On Fri, 30 Jan 2009 17:00:00 -0500, Saku Ytti <saku+nanog@ytti.fi> wrote:
>> Which standard are you referring to? AFAIK, nothing above 1500 is
>> standardised
>
> None that have ever been accepted. From a quick google for
> manufacturer support, 9216 looks like the most popular number. But,
> as I said, it boils down to the largest frame *every* device on the
> LAN will accept. If there is a single device that only supports
> "9000", then that's your limit. And if there's a single non-JF device
> in the LAN, it throws a wrench into the whole thing. (This appears to
> be one of the sticking points as to why IEEE won't accept the addition
> of JF to any specs.)
>
> --Ricky
>
> PS: The topic pops up again with super-jumbo frames in 10G networks.
>
For what it's worth, TCP will negiogate MSS and will work with
mismatched MTU in a single LAN segment. Other protocols (e.g. UDP) will
be borked though.
S
