The IPv4 Internet MTU (was Re: Teredo MTU logic)

[Rémi Denis-Courmont <rdenis@simphalempin.com>]

Le Monday 24 September 2007 11:57:00 Arnaud Ebalard, vous avez écrit :
> At the moment, my conclusion is that you have 2 solutions to
> solve the issue:
>
> 1) setting up a relay at the edge of the site with a higher MTU value
>    and statically configure clients
> 2) setting up a relay at the edge of the site _and_ a server that the
>    clients will use to acquire an higher MTU from.

After some more not-so-long thinking, what about:
3) get rough consensus that there are no paths on the IPv4 Internet with a MTU 
larger or equal to 1308 bytes (the current "outer" Teredo MTU), but smaller 
than 1348 bytes (or any slightly bigger value)? Then, it is safe to update 
everything to a bigger inner MTU of 1320 bytes (or more); it will not cause 
any extra on-path fragmentation. In fact, it will even diminish the overhead.

So my naive question of the day is:
Does anyone have any practical case for an IPv4 path MTU within [1308;1348[ ?

-- 
Rémi Denis-Courmont
http://www.remlab.net/