On 23/03/18 11:31, Dan Purgert wrote: > 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.
That's not what I see in the RFC. The DNS only seems to care about a tree of nodes with labels, not whether a particular node represents a host or a network or something else. So if the node in question has the label "com", and "All the other nodes" consist of just the root domain (with the null label), that should be sufficient. Even just the null label followed by (empty list) should be enough. What you say may well be what was intended, but it doesn't seem specific to me. I realise practical considerations may be different, but I don't see any more requirement than that in that RFC. Richard
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