Detecting a non-existent domain

Tue Sep 23 22:43:09 UTC 2003

On Tue, Sep 23, 2003 at 03:15:06PM -0700, David Schwartz wrote:
> 	As for 'fsck.de', a good argument can be made that this is not really a
> legal domain.

It's a perfectly valid domain registered with DE-NIC. DE-NIC offers two
types of domains: delegated and so-called "MX-only" domains, where up
to five (IIRC) RRs reside directly in the TLD zone file. Do a whois
lookup on whois.denic.de for fsck.de to see how this looks like.

> It's a host. Checking for an SOA is a good way to tell if a
> domain is valid, depending upon what you mean by 'domain' and 'valid'.

Your definition of "domain" is too narrow. A "valid domain" in common
context is a registered second level DNS label. It has no implication
on what is technically being done with this label. Some NICs like
DE-NIC impose restrictions upon registration though (domain has to
be delegated to a working and configured set of NSses or be a "MX-only"
domain).

Regards,
Daniel