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RE: draft-santesson-tls-ume Last Call comment

2006-03-20 16:00:44
I'm not disagreeing with anything in this discussion.

However I don't think we need to address this in the discussed document.
The username in the defined domain hint is an account name and not
necessarily a host name. Name restrictions in this case are thus
governed by user name restrictions for the accessed system.


Stefan Santesson
Program Manager, Standards Liaison
Windows Security


-----Original Message-----
From: Eric A. Hall [mailto:ehall(_at_)ehsco(_dot_)com]
Sent: den 7 mars 2006 21:06
To: Mark Andrews
Cc: Kurt D. Zeilenga; ietf(_at_)ietf(_dot_)org
Subject: Re: draft-santesson-tls-ume Last Call comment


On 3/7/2006 8:16 PM, Mark Andrews wrote:

    * Hostnames that are 254 and 255 characters long cannot be
    expressed in the DNS.

Actually hostnames are technically defined with a maximum of 63
characters
in total [RFC1123], and there have been some implementations of
/etc/hosts
that could not even do that (hence the rule).

But even ignoring that rule (which you shouldn't, if the idea is to
have a
meaningful data-type), there is also a maximum length limit inherent
in
SMTP's commands which make the maximum practical mail-domain somewhat
smaller than the DNS limit. For example, SMTP only requires maximum
mailbox of 254 octets, but that includes localpart and @ separator.
The
relationship between these different limits is undefined within SMTP
specs, but its there if you know about the inheritance.

When it is all said and done, max practical application of mailbox
address
is 63 chars for localpart, "@" separator, 63 chars for domain-part.
Anything beyond that runs afoul of one or more standards.

</pedantry>

--
Eric A. Hall
http://www.ehsco.com/
Internet Core Protocols
http://www.oreilly.com/catalog/coreprot/

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