[arin-ppml] IPv4 Depletion as an ARIN policy concern

[William Herrin]

On Fri, Oct 30, 2009 at 10:29 AM, Lee Howard <spiffnolee at yahoo.com> wrote:
> There are very few places
> where adding IPv6 might break something.

Lee,

I'm not sure how you figure that. The moment I publish a AAAA record
for my web site, your web browser on your IPv4/IPv6 dual-stacked
machine will attempt to connect to that AAAA record in preference to
any A records I've published, will it not?

So if I'm using an ARIN /48 and you're using Verizon, your attempt to
access my web server is going to hang with a retransmitting TCP SYN
for a while before it falls back to looking up the A records. Same if
I'm on one side of the IPv6 transit-free peering divide and you're on
the other. The divide they've been talking about over on NANOG where
just about everybody can get to HE but quite a few folks who can get
to HE can't get to each other. Same if you happen to have been
tinkering with 6to4, whose donated public relays are not especially
well meshed with the IPv6 Internet backbone. Same if either of us is
multihomed with IPv4 but only single-homed with IPv6 and the link that
does IPv6 is malfunctioning. Same if IPv6 growing pains are causing a
connectivity glitch at the moment. Same if the IPv6 deployment on your
LAN is in an intermediate state where the machines have global-scope
IPv6 addresses but don't yet have IPv6 connectivity to the world.
They've been discussing the rogue RA problem over on NANOG too.

With IPv6 turned on, I have to really depend on applications doing a
smart job falling back to IPv4 when historically applications tend to
do a poor job falling back to any second choice. And God help you if
the first choice gave a wrong answer instead of failing to respond.

Maybe it's just my COOP mindset, but it seems to me there are a lot of
ways that adding IPv6 to my servers can disrupt their IPv4 operation.


> I ask you, then: what would motivate you to provide IPv6 support
> on your servers?

Changes to all the software so that by default a dual stack system
tries IPv4 first. That way I can adequately mitigate any risk from
offering IPv6 as an initially second-class service.

Or, of course, if a substantial enough deployment of IPv6-only users
goes forward despite my own reluctance.

But I'm easy to motivate: I'll invest vast amounts of time on systems
of no immediate use merely because they interest me. Other people
expect (gasp) a prompt ROI.

Regards,
Bill Herrin


-- 
William D. Herrin ................ herrin at dirtside.com  bill at herrin.us
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