Subject: Re: [Inip-discuss] Domain Names

From: avri <[email-masked]>
Date: Fri, 22 Jan 2016 20:32:18 -0500

Only cname ignores it?

Sent from my T-Mobile 4G LTE Device

<div>-------- Original message --------</div><div>From: Andrew Sullivan <[email-masked]> </div><div>Date:01/22/2016  5:51 PM  (GMT-05:00) </div><div>To: [email-masked] </div><div>Cc:  </div><div>Subject: Re: [Inip-discuss] Domain Names </div><div>
</div>On Fri, Jan 22, 2016 at 03:02:50PM -0500, Avri Doria wrote:
> I had always understood that CLASS was broken in some sense in that the
> standard RR types ignored it.

The standard RR types don't ignore it.  A is defined only for IN, for instance.

A

-- 
Andrew Sullivan
[email-masked]

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From: Andrew Sullivan <[email-masked]>
Date: Sat, 23 Jan 2016 09:56:02 -0500

> Only cname ignores it?

No.  1035 says NS, SOA, CNAME, and PTR are all defined for every
class.  RFCs 4034 and 5155 defines the RRTYPEs for DNSSEC as
class-independent.  DNAME is also defined as class-insensitive in RFC
6672.  Some RRTYPE definitions appear not to specify their class.  For
instance, RFC 7344 specifes CDS, and it doesn't say what class it is
for.  Perhaps because it inherits the format of DS, we can assume it's
class-independent, but it isn't clear.  LOC specifically says that it
can be used in HS and CH classes, but says the semantics are
undefined, so it's not plain to me whether it's class-independent.  I
haven't surveyed everything.  Interestingly, the IANA RRTYPE registry
doesn't actually say for which class(es) an RRTYPE is defined.  That
seems like a bug.  (Yet another thing I failed to catch when DNSEXT
co-chair, I think, since we updated the IANA considerations during
that time.)

The class-insensitivity of CNAME and DNAME is another reason why
classes don't really work: since they both redirect the name, that
means that name aliasing in one class entails the same alias
relationship in every other class, which means that for practical
purposes the name spaces must be parallel at least around the point
where any alias is introduced.  So the operation of different classes
for the a given name can't be separated, and this makes classes at
best of questionable utility.

Best regards,

A

-- 
Andrew Sullivan
[email-masked]