Connectivity to an IPv6-only site

Leo Bicknell bicknell at
Fri Apr 23 14:33:21 CDT 2010

In a message written on Fri, Apr 23, 2010 at 01:08:30PM -0400, Valdis.Kletnieks at wrote:
> No, the problems are probably further back in time. We first started turning up
> IPv6 back in 1997 or so.  There's a *very* good chance that we turned it off a
> decade ago (or whenever people *first* started listing quad-A's in NS entries)
> due to breakage and never actually revisited it since then.  This would have
> been in the era of early 6bone and "your IPv6 connection is probably tromboned
> through Tokyo".

Back in that era there was a very real problem of islands.  That
is, a group would set up IPv6 internally but never connect to the
"Internet" (however you want to define that).  So they got a AAAA
and blackholed trying to reach it.

When you look at the content providers (Yahoo and Google tend to
speak about this) they are very concerned about this problem as end
users can make themselves islands fairly easily (an island of your
house, for instance).

While the numbers are troubling for them, they are actually really
good news.  Depending on who's number you believe and when somewhere
between 0.01% and 0.5% of end users are on unconnected islands.
Now, when you serve a billion page views a day, dropping 0.5% is a
huge concern; but it actually means the island problem has gotten
really small.

More importantly, those are end users who are islands.  Someone
who's airport is misconfigured making them appear to have IPv6 when
they do not.  Most of these folks don't run recursive name servers.
While I don't know of any hard data, I would expect the number of
nameservers in islands to be at least one, and perhaps two or three
orders of magnitude less.

So, in the context of publishing AAAA's for your nameservers, I think
things are extremely safe at this point.  If the recursive box on the
other end has IPv6 at all and tries to use the AAAA there is a very good
chance it will have working IPv6.

In the context of publshing AAAA's for your services (e.g. WWW),
you need to look at the Google and Yahoo stats network wide, look
at your own user base, and determine what level of breakage is
acceptable.  Keep in mind that IPv4 doesn't always work, so 0% is
an unachieveable goal.  :)

       Leo Bicknell - bicknell at - CCIE 3440
        PGP keys at
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