On Wed, Aug 31, 2022 at 11:28:01AM +0000, lloydwood@xxxxxxxxxxxxxxxxxxxxx wrote:
> A fully-qualified domain name has the trailing period. which is to
> say, 'first-hop.example.com.' which forces use of the top-level
> domain, and avoids resolving to e.g. a local .com.* domain set up
> within your local dns, which is possible alternate context.
>
> Anything else is only partially qualified.
This is a common misconception.
> Even Wikipedia gets this right at the moment;
Last I checked, the definition should be found in IETF documents, not
Wikipedia.
> RFC1035 could be clearer.
It looks quite clear to me:
For example, the IN-ADDR.ARPA domain ...
If this were only a relative name, it would be "an IN-ADDR.ARPA domain".
We should not confuse zone file presentation syntax with the concept at
hand.
- A fully qualified domain is one in which all the labels have been
specified, because this is implicit or explicit in context.
- A relative domain name is some set of prefix labels, relative to some
(possibly unspecified) suffix.
How we write fully qualified domain names is context-dependent. I might
note that nobody addresses email to this list by writing to
<ietf@xxxxxxxx.>.
RFC5321, RFC5322 and predecessors are quite clear that the FQDNs in SMTP
and message header email addresses do not end in a trailing period. The
same is, for example, also true of DNS-ID and email address SANs in
certificates.
If some contexts are ambiguous and support both relative and
fully-qualified names and provide for a way to be explicit about one or
the other, that's a property of the context, not FQDNs.
--
Viktor.
