On Wed, Sep 11, 2013 at 11:59 AM, Matthias Wimmer <m...@tthias.eu> wrote:
> Hi Anders,
>
>
> El 2013-09-11 09:41:42, Anders escribió:
> > A side note, I wonder why courier doesn't use IPv6 by default?
>
> +1 (Me and others already asked for that as well.)
>
> As I remember, Sam doesn't like this idea very much.
I'm guessing here:
A few years ago, there were some faulty home and small office routers
around, that pretended to have an IPv6 network, and also pretended to have
a default IPv6 route for da intarwebz, which only worked to and from the
router.
In essence, you had a local IPv6 network pretending to be a part of an IPv6
Internet, which it wasn't.
Some systems selected IPv6 as default, which resulted in all the expected
problems, especially for sites that had AAAA records, which then were
"down" or "unreachable".
I therefore disliked having IPv6 as a higher priority than IPv4 on systems
I had anything to do with.
Perhaps this is the rationale Sam had for disliking it?
In any case, Google decided to run their own study and tests of how IPv6
connectivity worked for those who used Google for searches, and found out
that the problem was negligible around 2010/2011.
Now, in 2013, IPv6 is actually not only eminently usable, but very good
sense. Lots of people are now on IPv6-only networks, and the number is
rising.
> I tried some
> patching of the code myself. But even if you change the preference in
> the code, you will often get IPv4 connections instead of IPv6 ones. The
> reason is, that often there are A records in the resolver cache after
> resolving MX records. You whould have to ignore these hints and force a
> AAAA resolving if no such records are known before. (Which will result
> in higher latency and more DNS load.)
>
The resolver cache times out after a while, records don't stick around
forever, unless the cache is fundamentally broken (hello, Microsoft), or
the record in question was misconfigured.
--
Jan
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