>The chain of authority means you can trace back the delegations of
>any domain on the real DNS through its parent and eventually you will
>come to a domain delegated by the IANA from the real root of the DNS.

You imply there is only one DNS.

Sorry. Doesn't work that way.
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>For example www.cyber.com.au has a chain of authority back to IANA,
>through Cybersource, then whoever is the authority for com.au, then
>Robert Elz who was delegated authority for au by the IANA.
>Cybersource has no obligations about adding entries for unrelated
>entities to the cyber.com.au name space.

Robert Elz has no obligation to add any entries under AU either.  He can
use it as his own personal domain is he wishes.

Fortunately when Elz was "allocated" the TLD, it was with an intent.

>For example, if Melbourne IT decided to treat com.au applicants on a
>discriminatory basis, Robert Elz could take away their authority to
>delegate com.au names.  If NetRegistry decided to discriminate among
>au.com applicants and say reject applications from their competitors,
>Network Solutions and the IANA most likely couldn't care less.

>I suspect those two examples (com.au and au.com) are very unlikely,
>but some people like to have confidence that there is some sort of
>oversight in the unlikely event that a registry goes rogue.

I think your examples are way off.  Unless the consumer complains to Robert
Elz, the "discrimination" goes unheard.  Every time I've heard of such a
complaint, it's gone unheeded.

So what's the difference?  Nothing.