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[idn] Fwd: Re: About name syntax
- To: idn@ops.ietf.org
- Subject: [idn] Fwd: Re: About name syntax
- From: Harald Tveit Alvestrand <Harald@Alvestrand.no>
- Date: Tue, 29 Feb 2000 00:03:30 +0100
- Delivery-date: Mon, 28 Feb 2000 15:00:49 -0800
- Envelope-to: idn-data@psg.com
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