[dns-operations] Introducing CNAME Flattening: RFC-Compliant CNAMEs at a Domain's Root

Anthony Eden anthony.eden at dnsimple.com
Fri Apr 4 10:23:12 UTC 2014

While CloudFlare did not give any credit to previous work done (which sort
of pisses me off, but whatever), they are essentially implementing the same
thing that Amazon did with their ALIAS implementation, the same thing that
we did with the DNSimple ALIAS implementation, and the same thing that
DNSMadeEasy did with ANAME records. It's simply synthesizing A records
based on a DNS resolution of the hostname that the customer entered. We
also synthesize AAAA records at DNSimple if the query type warrants it.

The use case is to support multiple records on a node where you would have
previously used a CNAME. The most obvious case is on the zone apex, but
it's also useful on subdomains where you want to define MX or TXT records.
In the era of platforms as a service, where they want to be able to provide
a host name where the IP address may change on a fairly regular basis.

Yes, this is probably not compatible with DNSSEC, I actually haven't tried
to reason through what will happen in that case since we don't support
DNSSEC at DNSimple.

I've been thinking about writing an RFC for this, but I've never actually
done it, and it will take some time to do, however I think defining how an
ALIAS record will synthesize its response is probably something we need at
this point. It will also need to describe how TTLs are respected, how A vs
AAAA vs CNAME questions are treated and what failure rules might be

Anthony Eden

On Fri, Apr 4, 2014 at 11:23 AM, Marco Davids (SIDN)
<marco.davids at sidn.nl>wrote:

> On 04-04-14 11:20, Stephane Bortzmeyer wrote:
> >
> >
> http://blog.cloudflare.com/introducing-cname-flattening-rfc-compliant-cnames-at-a-domains-root
> >
> > Funny idea
> Indeed.
> Until you want to use DNSSEC.
> --
> Marco
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