Return two locations or low TTL [was: DNS caches that support partitioning ?]

Mark Andrews marka at
Tue Aug 21 00:19:39 UTC 2012

In message <15BF47FF-9B3D-498B-A58B-F03853F0BA08 at>, "Patrick W. Gilmore" writes:
> On Aug 20, 2012, at 08:47 , Chris Adams <cmadams at> wrote:
> > Once upon a time, Patrick W. Gilmore <patrick at> said:
> >> * How many applications are even aware multiple addresses were =
> returned?
> >=20
> > Most anything that supports IPv6 should handle this correctly, since
> > getaddrinfo() will return a list of addresses to try.
> Ah, the amazing new call which destroys any possibility of randomness or =
> round robin or other ways of load balancing between A / AAAA records.
> Yes, all of us returning more than one A / AAAA record are hoping that =
> gets widely deployed instantly.  Or not.

The problem is not getaddrinfo().  The problem is that there isn't
a DNS type that reliably returns both IPv4 and IPv6 addresses so
there is no way for the DNS server to sort these addresses together.

AAAA could have done it if there had been agreement to publish
mapped A records from the very start.  That will have also helped
with turning off of IPv4.  One can fudge around the lack of this
type with SRV records.

Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at

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