Subject: RE: Enforcing unreachability of site local addresses

From: "Michel Py" <[email-masked]>
Date: Sat, 15 Feb 2003 20:57:21 -0800

Alan,

> Alan E. Beard wrote:
> No wonder we're at an impasse:  we have a blind-men-and-the-elephant
> problem here!

No. We know what the elephant looks like. This is not the issue. The
issue is that for the last eight years we have been trying to design an
animal that carries as much as an elephant, at the speed of a cheetah,
drinks as little as a camel, an possibly poops only in the toilet and
flushes when done.

> The common, underlying issue, as I see it, is:
> The use of PA space in end-user networks has the effect of imposing
> upon those networks functional burdens and restrictions in multiple
> areas which the managers of commercial end-user networks may be
> unwilling to tolerate. In consequence, we may need to reconsider
> our current address allocation practice, which relies principally
> on the PA model, in light of current user expectations, current
> state of the routing protocols and standards, and anticipated
> developments in routing and switching code.

Given the rest of your postings, this appears to be a rather
black-and-white view from the enterprise point of view. For the same
reason multi6 has failed by limiting the scope to site multihoming, this
approach is equally doomed to fail because it ignores the issues of
large operators.

There is some quality work that has been done in the field of PA
multihoming solutions as well, such as:
http://www.ietf.org/internet-drafts/draft-huitema-multi6-hosts-01.txt

Although the current IPv6 architecture indeed favors the large operator
over the enterprise to the point that the enterprise network manager's
feet feel the IPv6 water too cold to put more than the tip of the toe in
(and this needs more balance), the other side of this coin is that if
one wants to make a buck out of IPv6 today one has to look at Asia and
to a lesser extent Europe for markets that involves a large percentage
of mobile devices that are a good fit for the PA model.

No bucks, no Buck Rogers.

Michel.

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From: "Alan E. Beard" <[email-masked]>
Date: Sun, 16 Feb 2003 13:46:04 -0500 (EST)

Michel:

> drinks as little as a camel, an possibly poops only in the toilet and
In the context of the overall architecture and design of the protocol, you
are, of course, right. It seems a bit hyperbolic to suggest that we don't
have a reasonable conception of the overall architecture of IPv6. The
blind-men-and-the-elephant metaphor was advanced in the context of the
address allocation practices discussion. It does seem, at least to this
observer, that we have a number of groups working on discrete issues
which, in aggregate, may arise from a common root cause, and that an
acknowlegment of that common root cause has so far been, at best, tacit.

> approach is equally doomed to fail because it ignores the issues of
This criticism would be both valid and compelling if the proposal cited
above had been worded more narrowly than the text shows.  In fact, the
call for reconsideration does not ignore the interests of the large
operators: the specific text is :"in light of current user expectations".
Last time I looked, the class "user" subsumed the class of large
operators, as well as privately operated networks (commercial and
otherwise), academic networks, retail ISPs, and others.

Granted, the problem statement does include a specific reference to
commercial operators of private networks.  We have been dealing with a
number of technical issues which have adverse impact on that class of
network.  However, the deleterious effects are not limited to
privately-operated commercial end-user networks.  Perhaps a broader
problem statement is in order, but the fundamental issue remains.

If the call for reconsideration had been worded to exclude any one or more
of the classes of network users, or to be so narrowly specific as to
admit _only_ the interests of selected classes of network users, the
criticism of "black-and-white view from the enterprise point of view"
would be irrefutable; however, such is not the case, and the criticism
fails on that ground.

> http://www.ietf.org/internet-drafts/draft-huitema-multi6-hosts-01.txt
There is no suggestion (at least to my memory) that the work cited above,
and others of like character, should not be part of the solution space.
The specific work cited would be rendered inapplicable only if use of PA
space were abandoned entirely for all or most classes of users; since no
proposal to abandon PA exists (nor is any such proposal anticipated - more
on this below), we should reasonably expect work such as that cited above
to continue and, wherever shown technically sound, to see actual service
in production networks.

The general tenor of the comments above (and to some extent, of that
below)  appears to proceed from an assumption that the writer of the
original call for discussion (and, before the question is raised, I did
indeed write the text of the call for discussion) presupposes an outcome
similar to:  "abandon PA (largely or entirely); use PI as the preferred
addressing model; and leave the transport and service providers to deal
with the consequences, whatever they may be".  I can state from direct and
authoritative knowledge that the writer of the call for discussion
presupposes no particular outcome whatsoever. Furthermore, the writer of
the text of the call for discussion would be very likely to oppose any
outcome of sort suggested above as signally irresponsible, and unworkable
in practice, given the present state of our technologies. Given the way
the IESG, the IETF, and this working group opreate, it would be grossly
presumptous of any person to presuppose any particular outcome, or even to
hold expectations concerning the character or the outline of any such
outcome.

> of mobile devices that are a good fit for the PA model.
The statement immediately above seems a good summary of the general state
of our current address allocation philosophy and the technical issues
attendant thereunto. Yes, it would appear that PA space is probably
appropriate for several classes of use, and that use of PA space probably
should not be abandoned.  However, as pointed out above, more balance is
indeed needed with regard to address allocation policy for some classes of
users: it may not be desirable to continue to prefer PA allocations (to
the nearly total exclusion of other models) for at least some user
groups.

Let's talk the matter over, shall we?

> No bucks, no Buck Rogers.
Personal note:  Michel, your last paragraph above indicates, at least by
my interpretation, that you and I are really after the same objective: a
technically sound and balanced policy which will faciltate the widest
possible acceptance and implementation IPv6 in both pubic and private
networks.  Thank you for your comments, and for providing this opportunity
to correct any misapprehensions which may have arisen concerning the
nature and intent of the call for discussion.

Regards,

Alan

-- 
Alan E. Beard <[email-masked]>
AEBeard Consulting; 4109 Chelsa Ln; Lakeland FL 33809
863.815.2529