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Re: RFC2396bis, qualified, a nit

From: Roy T. Fielding <fielding@apache.org>
Date: Fri, 28 Feb 2003 17:12:11 -0800
Cc: uri@w3.org
To: Peter Koch <pk@TechFak.Uni-Bielefeld.DE>
Message-Id: <D4647567-4B82-11D7-B193-000393753936@apache.org>

>> Yep.  Theoretically speaking it matches the way BIND works, but I 
>> agree
>> that it is better for parsers as
>>
>>>    qualified     = *( "." domainlabel ) [ "." toplabel "." ]
>>
>> Added to the list as 038-qualified.  Thanks.
>
> In the DNS the trailing '.' is never part of the domain name. It is 
> only
> used in zone file format to explicitly declare a domain name as FQDN.

Actually, it is used anywhere that a resolver is used.  I have 
personally
used it in the past to differentiate between an ill-fated College of 
Medicine
subdomain "com" from the TLD com, for both e-mail and URI addressing.

> Also, it's currently true that TLD names do not start with digits, 
> there's
> nothing in 1123 (or 952) that would forbid this. Until 1123 was 
> published,
> a digit was not allowed as the first character of any label, but this 
> was
> what 1123 relaxed. The only remaining restriction in this direction is 
> that
> a hostname must not "look like" an IP (v4) address, i.e. it would be
> unwise to have a TLD consisting of digits only.

That was not the intent of 1123.  It allows all-numeric domain names 
only
because it is well-known that TLDs will never be allowed to be 
all-numeric.
It is therefore useful (and encouraged by 1034 and 1123) that we
syntactically distinguish IP addresses from domain names.

> I'd like to suggest that a hostname be either an FQDN (identified as 
> such
> by having at least one dot) or consist only of a single label. 
> Everything
> else is too dependent on the actual DNS searchlist strategy.

Sorry, there are no implementations that correspond to such a 
restriction.

....Roy
Received on Friday, 28 February 2003 20:46:06 GMT

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