A-label definition

[Mark Andrews]

> Mark Andrews wrote:
> 
> >> If you think it helps we could move RFC 952 to HISTORIC,
> >> it muddies the water when it shows up in ICANN documents
> >> published in 2008.
>  
> >> The decruft experiment (RFC 4450) missed RFC 952, because 
> >> it was limited to standards, excluding "status: unknown".
>  
> > It is the current RFC that limits hostnames to LDH.  -GW
> > and -NIC etc. are just shoulds not musts.
> 
> RFC 1035 claims that RFC 952 "specifies the format of 
> HOSTS.TXT, the host/address table replaced by the DNS."
>                                   ^^^^^^^^
	The DNS replaced hosts.txt as the distribution method.
	It did not change the syntax.

> RFC 1035 says "63", not "24", it is an Internet Standard, it
> was updated by RFC 1123, another STD.  And it defines LDH.
> 
> For what purpose do you onsider RFC 952 as current ? It has
> in essence the same LDH concept, only limited to "24".  I'm
> not *generally* opposed to old RFCs with an unknown status,
> but RFC 952 is (apparently) "de facto" obsolete.  It's just
> that nobody bothered to note the fact "officially" so far.

	RFC 1035 does NOT define hostnames.

	Hostnames, when stored in the DNS, are a subset of the
	available domain names in the DNS.

	Hostnames are allowed to be up to 255 characters in length
	and labels up to 63 characters (RFC 1123).

	The DNS is only capable of representing hostnames that are
	up to 253 characters in length which is what you get back
	to when you take the maximal wire format and convert it
	back into a presentation format that is only LDH for the
	labels.

	Hostnames don't have a trailing period.
	Domain names may have a trailing period.

	For a arbitary domain name the presentation format is anything
	up to ~1k in length.

	Even RFC 1123 says that hostname syntax is modified from RFC 952.

2.  GENERAL ISSUES

   This section contains general requirements that may be applicable to
   all application-layer protocols.

   2.1  Host Names and Numbers

      The syntax of a legal Internet host name was specified in RFC-952
      [DNS:4].  One aspect of host name syntax is hereby changed: the
      restriction on the first character is relaxed to allow either a
      letter or a digit.  Host software MUST support this more liberal
      syntax.

      Host software MUST handle host names of up to 63 characters and
      SHOULD handle host names of up to 255 characters.

	DNS domain names and hostnames are different things.  Most
	host names can be stored in and retrieved from the DNS.
 
> > To move RFC 952 to historic we need to write a RFC which
> > consolidates all the changes to hostnames: syntax, lengths
> > etc. into one document.
> 
> Okay, I wanted an "updates: 1123" for the <toplabel> issue,
> we don't need "updates: 1035" because RFC 1123 already did
> this, but adding "obsoletes: 952" to idnabis-rationale is
> a possibility.  But I don't see the necessity to justify an
> "obsoletes: 952" in an IDNAbis memo.  Unlike the <toplabel>
> bug, that is IMO required for IDNAbis, and it doesn't belong
> into say 2606bis.
> 
> We could of course also fix this bug in a separate IDNAbis
> memo, and while at it add an "obsoletes: 952" - short RFCs
> are good.  Is that what you propose ? 
> 
>  Frank
> 
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-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org