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From: [EMAIL PROTECTED] (Rahul Dhesi)
Newsgroups: comp.protocols.tcp-ip.domains
Subject: Re: NSI may revoke 100's of domains
Date: 14 Jan 2000 02:39:08 GMT
Organization: a2i network
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Message-ID: <85m28c$et6$[EMAIL PROTECTED]>
References: <854smh$[EMAIL PROTECTED]> <BXnd4.41$hP4.1734@burlma1-snr2>
<85kf40$599$[EMAIL PROTECTED]> <85kgdv$[EMAIL PROTECTED]>
<85kita$625$[EMAIL PROTECTED]> <[EMAIL PROTECTED]>
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Xref: ns3.vrx.net comp.protocols.tcp-ip.domains:9700
In <[EMAIL PROTECTED]>
[EMAIL PROTECTED] (Sam Wilson) writes:
>In article <85kita$625$[EMAIL PROTECTED]>, [EMAIL PROTECTED]
>(Rahul Dhesi) wrote:
>>In <85kgdv$[EMAIL PROTECTED]> [EMAIL PROTECTED] (Mark Andrews) writes:
>>
>>> It doesn't to me. Aliases also have to follow hostname syntax.
>>> see: RFC 952. Given that *only* record at webforward.ascio.net
>>> is an A record. www.a-.com can therefore be assumed to be an
>>> alias covered by RFC 952.
>>
>>The words 'cname' and 'alias' nowhere appear in RFC 952.
>Correct, but the word "nickname" does. Same function.
Well, maybe. But in any case, RFC 2181 supersedes RFC 952. And RFC 2181
says:
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 the emphasis, which I have added. The same RFC says
a little while later:
Clients of the DNS can impose whatever restrictions are appropriate o
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.
So, a name like a-.com is valid in DNS, but you are free to write a
program that refuses to use it.
>From the DNS perspective, every character value between 0 and 255 is
valid.
QED, EOP, EOD. Y2K.
--
Rahul Dhesi <[EMAIL PROTECTED]>
See my UUNET spam mini-faq at:
http://www.rahul.net/dhesi/uunet.faq.txt
