Subject: comment to draft-draves-ipngwg-router-selection-00.txt

From: Jun-ichiro itojun Hagino <[email-masked]>
Date: Tue, 20 Mar 2001 01:09:36 +0900

RA preference is very useful in the following very simple situations.
	your slide did not cover this, i believe this scenario is the most
	popular case.

itojun

a host is on a non-leaf network.
- if we throw RA from router A only, we will lose connectivity to "leaf"
  if router A goes down.
- if we throw RA from both router A and B, we have lots of icmp6 redirect
  if router B is picked as the default outgoing router for host C.

so what you will want to do is:
- set RA preference as router A > router B, advert from both.

upstream
  |
router A
  |
==+===============+==
  |		  |
router B	host C
  |
leaf

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From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Wed, 21 Mar 2001 08:17:15 +0900

>>>>> On Tue, 20 Mar 2001 01:09:36 +0900, 
>>>>> Jun-ichiro itojun Hagino <[email-masked]> said:

> 	your slide did not cover this, i believe this scenario is the most

It could also be used for a protection against misconfigured RAs.  For
example, even if a user mistakenly sends unauthorized RAs (and
administrators cannot easily detect where the source of the RAs is
located), the RAs could be overriden by authorized RAs with a higher
preference.

Note that I don't argue this story can be applied for DoS attacks,
where the attacker would set the preference field to the highest
value.  However, if the unauthorized RAs are just a result of
misconfiguration, we can expect that the preference value is the
default value, which can be overriden by a higher value (according to
the draft).

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					[email-masked]
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