On Fri, Oct 27, 2017 at 3:27 PM, Steve Atkins via dmarc-discuss
<dmarc-discuss@dmarc.org> wrote:
>
>> On Oct 27, 2017, at 3:20 PM, Brandon Long <bl...@google.com> wrote:
>>
>> Isn't .us usually considered a 3 level tld, like .uk and .au? And DMARC
>> says to ignore tlds.
>
> Neustar decided second level domains were more valuable 15 years ago or so,
> and it's mostly sold as a generic two level TLD now.
>
> Given the history there are still a lot of three and four level hostnames in
> there (states, .fed.us, .nsn.us, ...), and the weird
> {ci,co,city,...}.<locality>.<state>.us stuff so it's probably one of the more
> complex bits of organizational domain identification code.
The us TLD is horribly complex.
https://github.com/publicsuffix/list/pull/276 provides a hint of the
complexity -- there are more than 2000 non-overlapping suffixes for
.us and they vary. For example k12.az.us is a registered domain while
k12.ca.us is a suffix for registered domains. There are also "hybrid"
names due to the delegated managers system, where portions of the US
namespace are delegated to registrars who use completely separate
rules for registration.
Good luck on figuring out the domain boundaries under .us ;)
Thanks,
Peter
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