Re: Federated, decentralised communication on the internet

[Dan Purgert <dan@djph.net>]

Richard Hector wrote:
> On 23/03/18 01:17, Greg Wooledge wrote:
>> [...]
>> RFC 1594 <https://tools.ietf.org/html/rfc1594>: A Fully Qualified
>> Domain Name (FQDN) is a domain name that includes all higher level
>> domains relevant to the entity named.  If you think of the DNS as a
>> tree-structure with each node having its own label, a Fully Qualified
>> Domain Name for a specific node would be its label followed by the
>> labels of all the other nodes between it and the root of the tree.
>>
>> For example, for a host, a FQDN would include the string that
>> identifies the particular host, plus all domains of which the host is
>> a part up to and including the top-level domain (the root domain is
>> always null).
>
> Thanks - Having read that paragraph of the RFC, it doesn't seem to
> require any particular number of levels, only that all that exist are
> present.
>
> Richard

It requires two "levels"

 1. the TLD itself
 2. the named host

Therefore, "com." (that is, the TLD 'com') is not a valid FQDN. However,
"a.com." (that is, the host 'a' on the 'com' TLD) is a valid FQDN.

NOTE -> the trailing dot is only required in DNS entries, general
internet usage (email, [web|ftp|nntp|etc] services, etc.) do not require
it to be used (although, a quick test to slashdot, google, and sparkfun;
all three resolved properly with the trailing dot included). 


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