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Re: [idn] Proposed suggestions from Asia Pacific Top LevelDomain meeting
> 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:
Wrong. The title for Section 2.3.1 is "Preferred name
syntax". It describes a restricted subset of legal label
that are unlikely to cause problems. Any 8 bit values are
allowed (Section 3) and there is a presentation syntax
described mainly in Section 5 for how to represent non printing
ascii characters.
> "<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."
RFC1101 describes NETWORK NAMES not DOMAIN NAMES.
Network names are a *subset* of domain names the same as
host names are a subset of domain names.
>
> 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]
--
Mark Andrews, Nominum Inc. / Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: Mark.Andrews@nominum.com