5 ms·

> A fully qualified domain name includes a trailing dot The term is ambiguous, and many uses don't include the trailing dot. See IETF RFC 8499 section 2. > D

by dsp 6y ago

> A fully qualified domain name includes a trailing dot The term is ambiguous, and many uses don't include the trailing dot. See IETF RFC 8499 section 2. > DNS is strictly ASCII-only DNS is not strictly ascii. At the protocol level labels are octet strings. You may be thinking of the LDH convention.

cryptonector 6y ago
Correct. The ASCII constraint is for hostnames and domainnames, but not for all labels.
chrismorgan 6y ago
Thanks for the corrections. • Hmm, I wasn’t aware of that admission of ambiguity. Allowing that fuzziness in terminology puzzles me, because if you don’t have the trailing dot, then what you have fundamentally isn’t fully qualified. Sure, some resolvers may treat it as though it were, but some won’t, and are perfectly correct not to. (I haven’t the foggiest idea what the balance of implementation behaviours might be. I know enough DNS to be dangerous, but I don’t live and breathe the stuff.) • I should have said DNS hostnames are ASCII-only, which I believe to be true. (And yeah, this still depends on conventional rather than rigorously defined terminology.)
- jcrawfordor 6y ago
  The trailing-dot-to-anchor thing is hidden away from the user by probably a majority of tools now for managing DNS records. If anything, this has probably made the situation a bit worse by allowing a lot of people to spend years managing DNS records without even knowing about it. Then they edit a BIND text file or something that doesn't assume it and it all goes wrong. As far as client-side tools... no one ever uses the trailing dot and that can lead to some interesting situations if you have a search path set and use a resolver that resolves wildcard. Use of the search path at all is fairly unusual for "client-ish" setups though. You could also view the common non-use of the trailing dot as one of the causes of the ICANN recommendation against top-level domains resolving, as the search-vs-hostname-vs-fqdn ambiguity would be less common (but still present) if people commonly used the trailing dot.

by dsp 6y ago

cryptonector 6y ago

Correct. The ASCII constraint is for hostnames and domainnames, but not for all labels.

chrismorgan 6y ago

Thanks for the corrections. • Hmm, I wasn’t aware of that admission of ambiguity. Allowing that fuzziness in terminology puzzles me, because if you don’t have the trailing dot, then what you have fundamentally isn’t fully qualified. Sure, some resolvers may treat it as though it were, but some won’t, and are perfectly correct not to. (I haven’t the foggiest idea what the balance of implementation behaviours might be. I know enough DNS to be dangerous, but I don’t live and breathe the stuff.) • I should have said DNS hostnames are ASCII-only, which I believe to be true. (And yeah, this still depends on conventional rather than rigorously defined terminology.)

jcrawfordor 6y ago
The trailing-dot-to-anchor thing is hidden away from the user by probably a majority of tools now for managing DNS records. If anything, this has probably made the situation a bit worse by allowing a lot of people to spend years managing DNS records without even knowing about it. Then they edit a BIND text file or something that doesn't assume it and it all goes wrong. As far as client-side tools... no one ever uses the trailing dot and that can lead to some interesting situations if you have a search path set and use a resolver that resolves wildcard. Use of the search path at all is fairly unusual for "client-ish" setups though. You could also view the common non-use of the trailing dot as one of the causes of the ICANN recommendation against top-level domains resolving, as the search-vs-hostname-vs-fqdn ambiguity would be less common (but still present) if people commonly used the trailing dot.