Just what *is* a hostname (rfc952/1123, etc)
Barry Margolin
barmar at genuity.net
Wed Jan 23 21:24:20 UTC 2002
In article <a2n7aj$qjg at pub3.rc.vix.com>,
David Carmean <dlc-bu at halibut.com> wrote:
>
>On Wed, Jan 23, 2002 at 03:44:43PM +0000, Barry Margolin wrote:
>
>> David Carmean <dlc-bu at halibut.com> wrote:
>
>[snip]
>
>> >So far I haven't been able to figure out from the RFCs whether a
>> >hostname is just the leftmost label in a domain name, or whether
>> >the *entire* domain name (fully-qualified or relative) must be
>> >considered subject to the RFC952/1123 restrictions?
>>
>> What difference does it make? IIRC, the rules about hostnames apply to
>> each label, not the fully-qualified name.
>
>It seems to be perfectly legal to create a domain named "foo_b#r&.com.",
>if I'm reading RFC2181 correctly; the question is whether the name of
>any node in the entire subtree below that zone cut can be a legal
>Internet hostname.
I don't think so. The name of a node in that zone would be something like
hostx.foo_b#r&.com. The hostname rules apply to each and every label in
the name, and since the middle label breaks the rule, it's not a valid
hostname.
Perhaps a better way to answer this is that non-fully-qualified name are
just an abbreviation mechanism that can be used in certain contexts
(e.g. in zone files they're just a shorthand for the name with the $ORIGIN
appended, and when invoking a resolver it will try appending the suffixes
in the search list). As far as on-the-wire protocols are concerned, names
are always fully qualified.
--
Barry Margolin, barmar at genuity.net
Genuity, Woburn, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
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