Mark Andrews <marka@isc.org> writes:
In message <krmkg2$flc$1@ger.gmane.org>, Chris Hills writes:
Whilst I am not a fan of dotless domains, as long as one uses the fully qualified domain name (e.g. http://ac./), there should not be any trouble using it in any sane software. It seems that most people aren't aware these days that a fqdn includes the trailing period (by definition).
No it does not. Period at the end is a local convention to stop searching on some platforms. It is not syntactically legal. Note the words 'a sequence of domain labels separated by "."'. Periods at the end are NOT legal.
RFC 1738
host The fully qualified domain name of a network host, or its IP address as a set of four decimal digit groups separated by ".". Fully qualified domain names take the form as described in Section 3.5 of RFC 1034 [13] and Section 2.1 of RFC 1123 [5]: a sequence of domain labels separated by ".", each domain label starting and ending with an alphanumerical character and possibly also containing "-" characters. The rightmost domain label will never start with a digit, though, which syntactically distinguishes all domain names from the IP addresses.
That was fixed in RFC 2396: host = hostname | IPv4address hostname = *( domainlabel "." ) toplabel [ "." ] ... The rightmost domain label of a fully qualified domain name will never start with a digit, thus syntactically distinguishing domain names from IPv4 addresses, and may be followed by a single "." if it is necessary to distinguish between the complete domain name and any local domain. However, I think it's safe to say this is an edge case and chances are you'll have trouble using dotless domains with some software and processes. For example, you'll probably have trouble getting a SSL certificate.