On 05/07/2015 01:35, Andrew Sullivan wrote:
> Classes don't work in the general case, because CNAME (and following
> it, DNAME) is class-independent. This is arguably a bug in the
> protocol, but it's a fact nevertheless. As a result, different
> classes aren't really different namespaces.
Andrew,
Can you please elaborate on what you mean there?
Sure, CNAME is *defined* for all classes, but AFAIK there's no way to
"jump" out of one class into another using a CNAME. If you've queried
in class FOO and see a CNAME then the resolution of the target of the
CNAME should continue in class FOO.
RFC 1034 §3.6.2:
"CNAME RRs cause special action in DNS software. When a name server
fails to find a desired RR in the resource set associated with the
domain name, it checks to see if the resource set consists of a CNAME
record with a matching class. If so, the name server includes the CNAME
record in the response and restarts the query at the domain name
specified in the data field of the CNAME record."
kind regards,
Ray
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