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

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

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

> But why 1350 and not 1349 or 1351?

Why do you need a precise number? 1350 is low enough.

> > because the brokenness comes from tunnels.
>
> Brokenness comes from people filtering ICMP but still having PMTUD enabled.

That is still not true, at least not at the ISP level. There are NAT/load 
balancers which do not handle PMTUD properly even if all ICMP is allowed, 
and ICMP messages won't be generated when there are MTU mismatches.

Just because people keep blaming stupid admins for blocking ICMP doesn't 
mean it's the whole truth, there are plenty of manufacturers who get it 
wrong, and ISPs that misconfigure their devices (or the devices don't 
handle PMTUD/fragmentation properly at all).

> You confuse "works" with "right". That's exactly how the problem you try 
> to solve started. While I can imagine operators displaying this level of 
> pragmatism, we have to do better in the IETF.

Doing the "right" thing might be "right", but that doesn't mean it'll work 
in real life.

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