[Top] [All Lists]

Re: domain name definition in RFC2821

2007-03-21 14:04:02

Hi, Alex asked me to forward his reply to the SMTP list, see below.


Date: Tue, 20 Mar 2007 20:59:24 +0100
From: Alex van den Bogaerdt <alex(_at_)ergens(_dot_)op(_dot_)het(_dot_)net>
Content-Length: 1470

On Tue, Mar 20, 2007 at 05:41:55PM +0100, Frank Ellermann wrote:

I do not believe that there is any remaining question
about trailing periods on multiple-label FQDNs.  They
are prohibited.

+1 wrt SMTP (wrt SPF policies it's a different story)


I'm not subscribed to that list, so forgive me for replying
directly to you.  Please forward it to the list if you think
it is appropriate.

If I may quote a part of RFC3696:

"The DNS specification also permits a trailing period to be used to
 denote the root, e.g., "a.b.c" and "a.b.c." are equivalent, but the
 latter is more explicit and is required to be accepted by applications.
 This convention is especially important when a TLD name is being
 referred to directly.

is required to be accepted<<<

Are the 2821bis folks really going to make the same mistakes?

A TLD is a domain like any other.  Poor judgement from large companies
and such doesn't make a TLD less valid.  Besides, allowing a trailing
dot may actually help them, to distinguish between "" as
part of domain "" and ""
as the (existing) FQDN. (sorry for using an existing example!)

RFC 821 allowed one label (called "name").  It is 2821 that is flawed.

Together with the statement about trailing dot, <domain> should be:

<domain> ::= <label> [ "." ] | <label> "." <domain>
domain = *(label ".") tld ["."]