[dns-operations] Adding CNAME for the root domain issue

Andrew Sullivan ajs at anvilwalrusden.com
Fri Apr 29 19:55:33 UTC 2016

On Fri, Apr 29, 2016 at 03:30:22PM -0400, Andrew Boling wrote:
> The scope of the CNAME record has always been limited to a single label, as
> it was designed to alias host resources (not define equivalence in the DNS
> hierarchy).

I'm not sure I buy this account.  It was not designed to define
equivalence, it's true, but I think it might have been intended to do
more than alias host records (which in any case are less self-evident
than they might be, since A doesn't have the same semantics in every
class).  Mostly, they remind me of symlinks in the UNIX filesystem,
which have the same kind of problem: you can get to the target but
you don't know what is pointing at any given target.

> In short, CNAME does not provide this function, and without some EDNS
> hacking the rrtype cannot be updated to provide this function in a way that
> is backwards compatible.

Ugh!  The very idea terrifies me.

There have been proposals (one of which is BNAME) to create a new
RRTYPE that aliases the name and everything beneath it (e.g. they
function like CNAME+DNAME).  This didn't get very far, and I think the
reason is because once you start thinking about the sharp corners
nobody wants to implement such a thing.


Andrew Sullivan
ajs at anvilwalrusden.com

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