Subject: RE: Take 2: References/In-Reply-To replacement text

From: "Larry Osterman (Exchange)" <[email-masked]>
Date: Tue, 1 Jun 1999 11:46:18 -0700

> Larry> Thomas Oscar Theodore Osterman Sent from
> Larry> toto-laptop.dns.microsoft.com running NT5 and Outlook 2000 and
> Larry> Exchange Server 5.5.  Please notify the sender of any
> Larry> difficulties
> 
> OK, so am I talking to Thomas or Larry?

You didn't read the entire message closely enough - you read the punch line,
but not the setup.  The set up was:

>	Message-ID: <8BB128650D00D211BAEF00A0C9C74EB902E9E8@TOTO>

> In this case, the LHS of the ID is universally unique, even though the RHS
> isn't a FQDN.  So the text is simply stating that if your generation
> algorithm can guarantee uniqueness in the LHS, the thing on the RHS
doesn't
> HAVE to be a domain name, it could be anything (even the developers
initials
> :))

The punch line was:

> Larry> Thomas Oscar Theodore Osterman Sent from
> Larry> toto-laptop.dns.microsoft.com running NT5 and Outlook 2000 and

Anyway, as to your comment about the RHS of the @ in a mesage ID being
required to be a FQDN.  I don't understand this requirement at all.  It
seems to me that it would be a significant modification of the RFC822
grammar, and I can't see any technical requirements for it.

Larry Osterman
Sent from larryo-laptop.dns.microsoft.com running NT5 and Outlook 2000
and Exchange Server 5.5.  Please notify the sender of any difficulties

> 
> -- 
> Matt Curtin [email-masked] 
http://www.interhack.net/people/cmcurtin/

---

From: Matt Curtin <[email-masked]>
Date: Tue, 1 Jun 1999 15:43:42 -0400 (EDT)

>>>>> On Tue, 1 Jun 1999 11:46:18 -0700 ,
      "Larry Osterman (Exchange)" <[email-masked]> said:

Larry> Anyway, as to your comment about the RHS of the @ in a mesage
Larry> ID being required to be a FQDN.  I don't understand this
Larry> requirement at all.  It seems to me that it would be a
Larry> significant modification of the RFC822 grammar, and I can't see
Larry> any technical requirements for it.

How does the requirement for an FQDN in the RHS of a Message-ID modify
RFC822 grammar?

The reason that is a requirement is because it is the RHS that defines
authority.  That is, you may generate Message-IDs that are guaranteed
to be unique only within the scope in which you have any authority or
influence.  You have absolutely *no* way to prevent me, for example,
from generating Message-IDs whose LHS values are identical to yours.
The way that we solve such potential conflicts is to make the RHS of
the Message-ID an FQDN.

Your assertion that the RHS is insignificant given your scheme is only
valid when you assume that everyone on the planet is using your
scheme, which I assure you, will never be the case.

-- 
Matt Curtin [email-masked] http://www.interhack.net/people/cmcurtin/

---

From: Brad Knowles <[email-masked]>
Date: Tue, 1 Jun 1999 21:10:41 +0200

> grammar, and I can't see any technical requirements for it.

	Because there might be hundreds or thousands or even millions of 
machines out there named "toto", and there's a non-zero probability 
that one or more of them might have a different scheme of generating 
message-ids that could manage to collide with your scheme, unless you 
make the RHS sufficiently unique.

	I.e., you put on the machines FQDN, IP address, or something else 
that is pretty much guaranteed to be unique to that particular 
machine out of all others in the Universe -- and not just based on 
the grounds of probability, so don't even think about something like 
generating a "random" 128 bit quantity and appending that.

-- 
   These are my opinions -- not to be taken as official Skynet policy
  ____________________________________________________________________
|o| Brad Knowles, <[email-masked]>            Belgacom Skynet NV/SA |o|
|o| Systems Architect, News & FTP Admin      Rue Col. Bourg, 124   |o|
|o| Phone/Fax: +32-2-706.11.11/12.49         B-1140 Brussels       |o|
|o| http://www.skynet.be                     Belgium               |o|
\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
  Unix is like a wigwam -- no Gates, no Windows, and an Apache inside.
   Unix is very user-friendly.  It's just picky who its friends are.

---

From: [email-masked] (Kai Henningsen)
Date: 06 Jun 1999 17:35:00 +0200

> generating a "random" 128 bit quantity and appending that.

A pretty simple algorithm that should be good enough for a great many  
machines and use only locally available information would be as follows:

* find some piece of hardware that has an 48-bit or 64-bit IEEE id (such  
as an Ethernet MAC address). Use only those that don't have the local bit  
set, of course :-) [And in most cases, IPv6 machines will already have  
those ids in their IP addresses.]

* generate a @<long hex string>.MAC-48 or something like that pseudo- 
domain name, using said id.

(Similar ways could be used for any other unique identifiers, say  
@<phoneno>.PHONE-NO, that you happen to have available. Don't forget  
privacy concerns, though.)

MfG Kai