Re: draft-wbeebee-ipv6-cpe-router-04 comments

[Mikael Abrahamsson <swmike@swm.pp.se>]

On Mon, 20 Jul 2009, Iljitsch van Beijnum wrote:

> > I have actually set the MTU of this tunnel to 1350 which means this is the 
> > lowest common denominator for PMTUD (is my guess anyway)
>
> Why do you guess this?

Because the people who mess up usually have larger packet sizes than 1350, 
because the brokenness comes from tunnels. If I have a tunnel with 1350, 
the only likely even less MTU subnet I might come across is much more 
likely to get it right than the guys who try to run 1500 and get it wrong.

I do realise this isn't the right thing to do, but it works much better 
than doing nothing. So the question is, do we try to work around the 
brokenness or do we just do the right thing ourselves and call everybody 
else "broken" and sit there with a less working IPv6 than we could have.

> There are people who set their MTU to 576 in IPv4 (not too many anymore, I 
> hope) while the IPv6 minimum MTU is 1280. You can't win this by guessing.

I "win" more than if I stick to 1500 and experience all the brokenness.

So I think the question is, is this document about doing it right or 
getting it to work to the largest extent as possible?

--
Mikael Abrahamsson    email: swmike@swm.pp.se