[menog] IPv4 March 2011 depletion

Brian Candler B.Candler at pobox.com
Mon Nov 15 10:17:01 GMT 2010

On Sun, Nov 14, 2010 at 03:30:57PM -0800, Owen DeLong wrote:
>    What it really shows is that regardless of the transition technology in
>    question, shortly after RIR
>    runout, eye-ball providers are going to have customers with limited,
>    degraded, or no access

ISPs are concerned about keeping their customers happy and paying their
bills, and they will deploy whatever option achieves that. Options include:

(1) Customers can be given RFC1918 space behind a regular IPv4 NAT (the
model which most mobile phone companies use today).

98% of customers won't even notice. 1% will consider it to be a security
benefit.  The remaining 1% will pay more for a premium product with a real
IP address.

(2) Even when all IP address space has been *allocated*, only a small
portion of it will be *in use*.

ISPs will be able to buy additional IP address space from organisations not
using it, at market rates.  The figure I've heard suggested is a one-off
charge of $16 per IP address.  This is very cheap compared to the cost of a
DSLAM or MSAN port, and can easily be absorbed for as long as it stays that

In my opinion, the business realities today are:

- no sane ISP will flip their *existing* customers over to an IPv6-only
service (even with NAT64), or any service which requires the customer to
replace their CPE or their PC.

- if ISPs start selling IPv6-only services to *new* customers, and those
customers find they won't work with their existing equipment, then they will
immediately walk to a different ISP.  The customers won't understand the
underlying technical issues; all they'll understand is that one ISP lets
them connect to The Internet and another one doesn't.

Rolling out V6 is therefore a business decision, not a technical one, and
will be made by business managers.  If delaying V6 gives them an advantage
in the marketplace, that's what they'll do.  It's a Poker game.

>    This is why many of us are saying that the most critical step today is
>    to get as much of the
>    public facing services and content on IPv6 as possible as soon as
>    possible.

I disagree, because in the absence of a central Internet authority, it's
unachievable.  There are a few big content providers but millions of small
ones.  You're also assuming that these content providers will feel compelled
to turn on V6 to avoid losing eyeballs, when in practice the eyeballs aren't

Even those content providers who enable V6 are also going to make it
available on V4 forever(*). Given that 100% of the content will be on V4,
the critical step is therefore providing usable access to The (V4) Internet
from V6 users.

I can see only one strategy which might work for V6 rollout: the ISP needs to
provide access circuits with dual-stack RFC1918 NAT44 + V6 with NAT64 (**).

This supports the following use cases:
1. existing CPE and workstations (V4 only)
2. new V6-only users, which is where you want the growth to be
3. dual-stack endpoints

Note that if this happens, then for a very long time there will be a lot of
'accidental' dual-stack endpoints.  Unless you explicitly turn off V4, most
devices will pick up both V4 and V6 addresses if that's what their network
offers them.  Furthermore, manufacturers will continue to build devices that
way for the foreseeable future.

Hence it's critical that NAT64 be able to function alongside NAT44.



(*) "Forever" in the context of The Internet is 10 years plus.

(**) And they will also offer a per-user setting to turn V6 off or on. This
is because some existing equipment may crash when V6 is presented to it, and
some users may wish to have under their own control when it is turned on,
especially existing customers.

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