Re: mech-v2: static MTU scope; feedback sought

[Pekka Savola <pekkas@netcore.fi>]

On Fri, 30 Jan 2004, Jun-ichiro itojun Hagino wrote:
> > On the other hand, there have been comments on the contrary, that 
> > mismatching MTU/MRU is a bad thing, like pointed out by itojun.  I 
> > remember the message but have been unable to find the message referred 
> > to in:
> > 
> > http://ops.ietf.org/lists/v6ops/v6ops.2003/msg01718.html

Thanks for getting back at this.
 
> 	the operational problem we have experienced was between KAME and
> 	Juniper.  Juniper (JunOS) sets tunnel MTU to infinity by default, and
> 	KAME defaults to 1280.  with this setup ICMPv6 "need fragment" was
> 	not generated (don't remember from which end), and tunnel between
> 	Juniper and KAME did not work well too.  setting Juniper's MTU to
> 	1280 solved the problem.

Well, not anymore at least.  The default MTU is 1480 (I think it has
been that for at least a year, but we don't do a lot of tunneling, so
I don't know), so this should not be a problem as long as the other
end has large enough MRU to receive packets of this size.

Needs to be spelled out though.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings