[idn] Fwd: Re: About name syntax

[Harald Tveit Alvestrand <Harald@Alvestrand.no>]

I found the quote below worth repeating here.

It seems that we already have what we want in the "DNS transport layer": A 
mechanism that doesn't care what the content of records are.

The only exception I think I know about is that caches will do ASCII case 
folding when matching names.

                     Harald


>From: Randy Bush <randy@psg.com>
>To: dfernan1@airtel.es
>Cc: namedroppers@internic.net
>Subject: Re: About name syntax
>Date: Mon, 28 Feb 2000 09:00:00 -0800
>Sender: owner-namedroppers@ops.ietf.org
>
> > In RFC 1035 parragraph 2.3.1. ("Preferred name syntax") recomended
> > characters for domain names are a-z, A-Z, 0-9 and "-". What kind of
> > problems could i find if i used the "/" char inside a host name (for
> > example the/host.my.domain).?
>
>rfc 2181
>
>11. Name syntax
>
>    Occasionally it is assumed that the Domain Name System serves only
>    the purpose of mapping Internet host names to data, and mapping
>    Internet addresses to host names.  This is not correct, the DNS is a
>    general (if somewhat limited) hierarchical database, and can store
>    almost any kind of data, for almost any purpose.
>
>    The DNS itself places only one restriction on the particular labels
>    that can be used to identify resource records.  That one restriction
>    relates to the length of the label and the full name.  The length of
>    any one label is limited to between 1 and 63 octets.  A full domain
>    name is limited to 255 octets (including the separators).  The zero
>    length full name is defined as representing the root of the DNS tree,
>    and is typically written and displayed as ".".  Those restrictions
>    aside, any binary string whatever can be used as the label of any
>    resource record.  Similarly, any binary string can serve as the value
>    of any record that includes a domain name as some or all of its value
>    (SOA, NS, MX, PTR, CNAME, and any others that may be added).
>    Implementations of the DNS protocols must not place any restrictions
>    on the labels that can be used.  In particular, DNS servers must not
>    refuse to serve a zone because it contains labels that might not be
>    acceptable to some DNS client programs.  A DNS server may be
>    configurable to issue warnings when loading, or even to refuse to
>    load, a primary zone containing labels that might be considered
>    questionable, however this should not happen by default.
>
>    Note however, that the various applications that make use of DNS data
>    can have restrictions imposed on what particular values are
>    acceptable in their environment.  For example, that any binary label
>    can have an MX record does not imply that any binary name can be used
>    as the host part of an e-mail address.  Clients of the DNS can impose
>    whatever restrictions are appropriate to their circumstances on the
>    values they use as keys for DNS lookup requests, and on the values
>    returned by the DNS.  If the client has such restrictions, it is
>    solely responsible for validating the data from the DNS to ensure
>    that it conforms before it makes any use of that data.
>
>
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--
Harald Tveit Alvestrand, EDB Maxware, Norway
Harald.Alvestrand@edb.maxware.no