Re: [sig-policy] [Sig-policy] prop-062-v001: Use of final /8
On Jul 31, 2008, at 5:33 AM, David Woodgate wrote:
Tom,
I appreciated your feedback - thank you for some well-reasoned points.
Your response highlighted for me that while we as an industry are
giving some attention as to how to get networks *onto* IPv6, I'm not
sure that much thought has been given as to how we will ultimately
get them *off* IPv4. What will be the criteria identifying when a
network can be connected to the Internet only using IPv6, without
any IPv4, and be confident of at least > 95% connectivity? In what
year will this point be reached?
Hi David,
That's a good question, one that merits more thought by the broader
community. That said, it seems like a more fruitful way to approach
the question would be to identify a set of tools which which one might
track the evolving share of IPv4 hosts or ASNs (or more ambitiously,
"important" IPv4 hosts/ASNs) that are reachable by some "meaningful"
sample of IPv6 hosts over time. Something like the Routeviews Archive
with additional functions maybe...
Given the likelihood that Internet access providers will wish to adapt
their access services to the evolving connectivity landscape, it
wouldn't be surprising if many chose to set up the equivalent of
"wardialers" to regularly evaluate reachability and performance
conditions between their own IPv6 end sites and a sampling of popular
online destinations. If an archive of data like this generated by
commercial operators (or barring that, perhaps a similar collection of
results generated by multiple RIRs and/or other neutral, noncommercial
entities) could be collected in some public repository, it should be
possible to compare reachability from IPv6 hosts to reachability from
IPv4 hosts, and thus to develop a kind of "substitutability metric" to
illuminate how close IPv6 is to being "as good as" IPv4 as a means of
attachment to the Internet over time.
One danger that I see in reserving a lot of IPv4 addresses to enable
IPv6 network connectivity without a clear exhaustion or sunset date
is that it may in fact remove industry incentive to move off IPv4 -
and I don't think we should be encouraging perpetual dual-stacking
in the Internet.
I agree, but the only alternative that I can imagine is a gradual but
absolutely certain globally coordinated phase-out of IPv4 entirely. I
can imagine ways to engineer incentives in order to promote an outcome
like this, and I can even imagine reasons why such an approach might
be attractive, even to most incumbent IPv4 operators, over the long
term -- but my imagination fails when trying to come up with
incentives that might be sufficient to overcome near-term discomfort
that such an approach would inevitably create, especially among the
largest IPv4 holders.
[For example, we seem to be assuming that the responsibility IPv6-
>IPv4 translation lies with a new edge or stub network that is
otherwise IPv6. However, if IPv4 is ultimately to be removed, it
seems to me that there needs to come a point (when the deployment of
IPv6 is substantial) where it becomes the implied responsibility of
the legacy IPv4 networks (or their transit providers) to do IPv4-
>IPv6 translation. Otherwise, the IPv4 networks would be able to sit
there for ever and just say "well, *we* don't need to change - we've
been here for all these years and everyone has to connect to us as
we are!". I admit that I don't immediately perceive what possible
changes in market conditions would enable such a transition from the
first state to the second.]
It seems that you have arrived at the same failure of imagination that
I described above ;-)
I would agree that prop-062-v001 "envisions" (i.e., anticipates, but
might also contribute to, marginally) a long transition period.
However, given the perverse incentives that will accompany any/all of
the most likely / most anticipated outcomes (e.g., creation of an IPv4
transfer market, or just continuation of the status quo until the end,
etc.), even a long transition is an improvement over the real
possibilities of a closed industry (aka inevitable external
intervention) and/or no transition, ever.
All that said, I have indicated in my previous emails that I would
be more sympathetic towards proposals that explicitly linked IPv4
allocations to IPv6 planning (especially one that effectively
supported multiple IPv6 hosts per IPv4 address). I do not believe
prop-062 does this - it implies an intent towards that, but it does
not actually specify any direct association between an applicant's
IPv6 status and an IPv4 allocation, and I suggest that there is a
lack of a critical assessment as to why a uniform allocation of a /
22 is the best approach.
The type of issues I believe should be considered by an IPv6-focused
proposal would include:
- A specification of the IPv6 and general criteria on which the IPv4
allocation would be dependent.
- A discussion of the criteria governing the appropriate size of an
IPv4 allocation
- A discussion of the amount of space that should be reserved for
this proposal, with the reasoning behind that amount (assumptions,
forecasts, etc.).
I'll defer to the proposal's authors on these points, but IMO they all
seem reasonable and modest enough to work through before the Christ
Church meeting...
- A sunset clause - a date after which any remaining addresses would
be made available for allocation by justified request. This could be
a far-away date like 31 Dec 2020 or longer - if we get it right,
then no one will want IPv4 addresses after the nominated date, and
if we get it wrong there should be plenty of time to change the
policy.
To me at least, 2020 seems wildly, unimaginably optimistic based on
current facts. Since the goal of the proposal is itself self-limiting
-- i.e., keep some IPv4 available to new entrants for as long as IPv4
remains demonstrably non-substitutable, and not one day more, I'd
prefer to see some actual empirical basis for sunsetting, e.g.,
something like the metric you suggested in passing above.
Additionally, it makes sense (to me at least) to leave the question of
what to do with any IPv4 remaining after prop-062-v001 sunsets to be
determined by community members at, or at least closer to that time.
Defining appropriate sunset conditions for the policy within the
policy itself seems like a good idea, but that would seem to preclude
the idea of incorporating additional details that dictate conditions
afterward. As you suggest, best to leave that for another day and
another, separate policy proposal.
(It's just as well that the proposal deadline for APNIC 26 is past,
or I'd be in danger of having to write up such a proposal! :-) )
One idea that has occurred to me is that maybe APNIC should not
allow members to directly request addresses from the reserved IPv4
space associated with such a revised proposal, but instead should
only make such IPv4 addresses optionally available as part of an
IPv6 address request. (In other words, there would be no further
IPv4-only allocations from the time of activation of the proposal,
only IPv6-allocations with some IPv4 addresses.) I admit I haven't
had time to think through whether this is a good or bad idea.
That's consistent with the point I made in our last exchange, i.e.,
"To be perfectly honest, the reservation fulfills this purpose most
clearly for new entrants -- i.e., "initial" allocation seekers -- but
the decision to make it non-exclusively available on a one-time-only
basis to all comers makes sense as a lightweight, pragmatic solution
to potential complications like determining eligibility, etc."
Clearly, the proposal's authors have a slightly different/more
expansive rationale in mind, so I'll look forward to hearing from them
on this point. But in general I agree that the compelling
justification for the policy/reservation is to facilitate IPv6
incorporation/transition, so making this connection more explicit in
the text of the proposal would represent (just) a modest but useful
clarification.
Regards,
TV