Should host/domain names travel over the internet with a trailing dot?

Mon Feb 25 23:54:37 UTC 2013

In message <17812038.7306.1361835383974.JavaMail.root at benjamin.baylink.com>, Ja
y Ashworth writes:
> ----- Original Message -----
> > From: "Mark Andrews" <marka at isc.org>
> 
> > > > No. See RFC 952
> > >
> > > I think 952 is functionally obsolete, requireing a <24 char name
> > > length;
> > > I would have expected citations, perhaps, to 1535.
> > >
> > > Care to expand?
> > 
> > Ok. RFC 952 as modified by RFC 1123. This covers all legal hostnames
> > in use today including those that do not fit in the DNS. The DNS
> > supports hostnames up to 253 bytes (255 bytes in wire encoding).
> > RFC 1123 allow hostnames to go to 255 bytes. I'm deliberately
> > ignoring IDN's as they still need to map back into what is permitted
> > by RFC 952 as modified by RFC 1123.
> 
> And except on length and first-digit-allowed, 1123 punts naming to 952 
> (which doesn't really say) and in 6.1, to 1034 and 1035.  So I know what
> my light night reading will be (unless Albitz, Liu, Mockapetris, or any 
> of the BIND team are around on the list :-)

952 says hostnames don't end in a period.

			  Note that periods are only allowed when
   they serve to delimit components of "domain style names". 

      <hname> ::= <name>*["."<name>]
      <name>  ::= <let>[*[<let-or-digit-or-hyphen>]<let-or-digit>]

1123 turned <name> into

      <name>  ::= <let-or-digit>[*[<let-or-digit-or-hyphen>]<let-or-digit>]

it also banned all digit tlds (no covered in the grammar).

> > RFC 1535 is NOT a STANDARD. Not all RFC are created equal.
> 
> Typo.  1035 (as updated by whatever is on-point, if anything).

And 1035 refers you to 952 + 1123 for hostnames.

However, when assigning a domain name for an object, the prudent user
will select a name which satisfies both the rules of the domain system
and any existing rules for the object, whether these rules are published
or implied by existing programs.

For example, when naming a mail domain, the user should satisfy both the
rules of this memo and those in RFC-822.  When creating a new host name,
the old rules for HOSTS.TXT should be followed.  This avoids problems
when old software is converted to use domain names.

	HOSTS.TXT == RFC 952.

Host names and domain names are not interchangable in all contexts.
You need to know the subtle differences and when which rules apply.
Lots of rfcs fail to make the proper distinctions and use domain
name when they mean domain style hostname.

Mark

> And Mark: could you please trim your quoting a bit?
> 
> Cheers,
> -- jra
> -- 
> Jay R. Ashworth                  Baylink                       jra at baylink.co
> m
> Designer                     The Things I Think                       RFC 210
> 0
> Ashworth & Associates     http://baylink.pitas.com         2000 Land Rover DI
> I
> St Petersburg FL USA               #natog                      +1 727 647 127
> 4
> 
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org