Subject: RE: "Default Address Selection for IPv6"

From: "Richard Draves" <[email-masked]>
Date: Sun, 9 Dec 2001 21:17:28 -0800

> - The longest matching algorithm is not so meaningful in the
>   destination address ordering.

Well, I think it is quite meaningful. It can certainly go awry (per your earlier example), but I think more commonly it will be helpful. For example, if node A is part of a multihomed site and so has two global address P::a and Q::a (from ISP's P and Q) and node B is connected via ISP P and so has the global address P::b, then when node B connects to node A the longest-matching prefix heuristic in the destination address ordering will cause node B to first try P::a and then Q::a.
 
Rich
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From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Tue, 11 Dec 2001 05:03:36 +0900

>>>>> On Sun, 9 Dec 2001 21:17:28 -0800, 
>>>>> "Richard Draves" <[email-masked]> said:

> Well, I think it is quite meaningful. It can certainly go awry (per
> your earlier example), but I think more commonly it will be
> helpful. For example, if node A is part of a multihomed site and so
> has two global address P::a and Q::a (from ISP's P and Q) and node B
> is connected via ISP P and so has the global address P::b, then when
> node B connects to node A the longest-matching prefix heuristic in
> the destination address ordering will cause node B to first try P::a
> and then Q::a.

Ah, yes, you're right.  I just missed the symmetric story of the
source address selection among multiple candidates.

So, IMO, the point is

  do we need the explicit longest matching while the generic policy
  table can do this and the effective prefix length can vary even
  today?

I myself do not have a strong opinion on this, but if I need to vote,
I'll be for leaving the current spec.

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