W3C home > Mailing lists > Public > uri@w3.org > March 2003

Re: RFC2396bis, qualified, a nit

From: Peter Koch <pk@TechFak.Uni-Bielefeld.DE>
Date: Mon, 03 Mar 2003 13:53:06 +0100
Message-Id: <200303031253.h23Cr6K28930@grimsvotn.TechFak.Uni-Bielefeld.DE>
To: "Roy T. Fielding" <fielding@apache.org>
Cc: uri@w3.org

> > 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 

That makes it a resolver side convention, not a part of the domain name.
The trailing dot simply doesn't belong there.

> 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.

Then you were lucky it worked, as you are if you use an Umlaut in an email
address or an IP address as a target of an MX RR. It may work and may have
worked for a long time but still it doesn't mean it's syntactically
If you're thinking of section of RFC 1123, that explicitly deals with
the user interface only.

> > 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 

The intent was to allow for domain names like "3com.com". I do not think
many people had in mind defining or even restricting future TLDs back then.

> because it is well-known that TLDs will never be allowed to be 
> all-numeric.

This is an operational or administrative convention, but it's not written
down in any DNS spec I am aware of (One should take section 2.1 of 1123 with
a grain of salt here.), so I doubt it's a good idea to make this assumption
for the URI spec.

Received on Monday, 3 March 2003 07:54:28 UTC

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