[137156] in North American Network Operators' Group
Re: Too bigs are sacred, was: Re: IPv6 addressing for core network
daemon@ATHENA.MIT.EDU (Owen DeLong)
Wed Feb 9 17:13:57 2011
From: Owen DeLong <owen@delong.com>
In-Reply-To: <iiuk5b$502$1@dough.gmane.org>
Date: Wed, 9 Feb 2011 14:11:32 -0800
To: David Freedman <david.freedman@uk.clara.net>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Feb 9, 2011, at 9:50 AM, David Freedman wrote:
> Iljitsch van Beijnum wrote:
>> On 9 feb 2011, at 18:30, David Freedman wrote:
>>=20
>>> (yes, even ICMP TOOBIG
>>> can be filtered safely if you have designed things in a sane way)
>>=20
>> NO.
>>=20
>> Even if you run with 1280-byte MTUs everywhere so you'd think path =
MTU discovery wouldn't be needed, this can still cause problems with =
IPv6-to-IPv4 translators.
>>=20
>=20
> Calm down, I think you misunderstand,
>=20
> I'm suggesting that you don't design your infrastructure in such a way
> that your backbone/infrastructure links ever have to receive TOOBIG
> messages from outside your AS and work with these, your backbone links
> are of course free to send TOOBIG out!
>=20
> Dave.
>=20
> --=20
>=20
>=20
> David Freedman
> Group Network Engineering
> Claranet Group
>=20
Unless every packet you emit is =E2=89=A4 the minimum MTU (1280), then, =
you need
to be able to receive TOOBIG messages.
Owen
