[149801] in North American Network Operators' Group
Re: Common operational misconceptions
daemon@ATHENA.MIT.EDU (Mark Andrews)
Wed Feb 15 23:30:28 2012
To: Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp>
From: Mark Andrews <marka@isc.org>
In-reply-to: Your message of "Thu, 16 Feb 2012 12:24:05 +0900."
<4F3C76D5.9040603@necom830.hpcl.titech.ac.jp>
Date: Thu, 16 Feb 2012 15:27:39 +1100
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
In message <4F3C76D5.9040603@necom830.hpcl.titech.ac.jp>, Masataka Ohta writes:
> Mark Andrews wrote:
>
> > This doesn't prove that IPv6 is not operational. All it proves is
> > people can misconfigure things.
>
> How do operators configure their equipments to treat
> ICMP packet too big generated against multicast and
> unicast?
Well you need to go out of your way to get a ICMP PTB for IPv6
multicast as the default is to fragment multicast packets at the
source at network minimum mtu (RFC3542 - May 2003). That's not to
say it won't happen.
As for generation of PTB you rate limit them the way you do for
IPv4.
> Note that, even if they do not enable inter-subnet
> multicast in their domains, the ICMP packets may
> still transit over or implode within their domains.
>
> Note also that some network processors can't efficiently
> distinguish ICMP packets generated against multicast and
> unicast.
And why do you need to distingish them? You look at the inner
packet not the ICMP source if you want to rate limit return traffic.
> Masataka Ohta
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: marka@isc.org
