RE: [idn] Proposed suggestions from Asia Pacific Top LevelDomain meeting

["Hollenbeck, Scott" <shollenb@netsol.com>]

Mark's comment below about domain name vs. host name character restrictions
made me wonder.  Please consider the following chain of RFC references,
which seem to imply otherwise:

RFC952: Describes host name syntax:
"1. A "name" (Net, Host, Gateway, or Domain name) is a text string up
to 24 characters drawn from the alphabet (A-Z), digits (0-9), minus
sign (-), and period (.).  Note that periods are only allowed when
they serve to delimit components of "domain style names". (See
RFC-921, "Domain Name System Implementation Schedule", for
background).  No blank or space characters are permitted as part of a
name. No distinction is made between upper and lower case.  The first
character must be an alpha character.  The last character must not be
a minus sign or period."

RFC1035: Section 2.3.1 describes label syntax for domain names:
"<label> ::= <letter> [ [ <ldh-str> ] <let-dig> ]"

RFC1101: Describes allowances for domain names that begin with a digit:
"For these reasons, we assume that the syntax of network names will be
the same as the expanded syntax for host names permitted in [HR].
The new syntax expands the set of names to allow leading digits, so
long as the resulting representations do not conflict with IP
addresses in decimal octet form.  For example, 3Com.COM and 3M.COM
are now legal, although 26.0.0.73.COM is not.  See [HR] for details."

The [HR] reference is to what eventually became RFC1123.

RFC1123: Updates host name syntax specifications:
"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."

My read of the above per RFC1101 is that there are limits on the characters
that can appear in domain names, even if the DNS specifies only limits on
length.  Did I miss something that points in another direction?

Scott Hollenbeck (mailto:shollenb@netsol.com)
Network Solutions, Inc. Registry

-----Original Message-----
From: Mark.Andrews@nominum.com [mailto:Mark.Andrews@nominum.com]
Sent: Monday, March 06, 2000 6:01 AM
To: Dan Oscarsson
Cc: phoffman@imc.org; jseng@pobox.org.sg; dlee@icu.ac.kr;
idn@ops.ietf.org; iname@aptld.org; bill@mail.nic.nu;
konishi@jp.apan.net; kwu@yam.com; syhan@cclab.konkuk.ac.kr;
markk@netsol.com; zwh@cnnic.net.cn; chang@netpia.com;
tinwee@pobox.org.sg; chon@cosmos.kaist.ac.kr; bmanning@isi.edu;
kwu@yam.com.tw
Subject: Re: [idn] Proposed suggestions from Asia Pacific Top
LevelDomain meeting 



> >And thanks to Mark, I finally understood the difference between domain
name
> >and host name. We havent even reach that defination yet...
> 
> So what is the difference?
> For me a host name is the name of a host while a domain name
> can be the name of a host or of many other things.

	Not bad for a first level answer.  For the second level you
	need to remember that host names have a MUCH more restricted
	syntax to domain names.

	Currently domain names have no restrictions on what is a legal
	character (8bit).  The only restrictions are total and label
	lengths.  Host names on the other hand are restricted to A-Z, 
	0-9, "-" and "." case insensitive.  "." is only allowed between
	labels.

[snip]