Re: Last Call: draft-klensin-rfc2821bis
John C Klensin <john-ietf@jck.com> Mon, 31 March 2008 03:53 UTC
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Date: Sun, 30 Mar 2008 23:53:37 -0400
From: John C Klensin <john-ietf@jck.com>
To: Mark Andrews <Mark_Andrews@isc.org>
Subject: Re: Last Call: draft-klensin-rfc2821bis
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I'm no longer going to comment on the mail aspects of this MX debate on the IETF list -- see the ietf-smtp list. But there is an issue here with much broader implications... --On Monday, March 31, 2008 9:36 AM +1000 Mark Andrews <Mark_Andrews@isc.org> wrote: >... > It's a natural back port of the SRV rules to MX. > > "SRV 0 0 ." indicates "no service". Well, strictly speaking, it doesn't mean that, regardless of what the SRV specs say. What is means is "this service is not advertised for this domain". If a service is associated, as part of its protocol, with an established (not necessarily well-known) port, then the only way to determine that the service isn't offered is by attempting to connect to that port. If is isn't associated with a specific port, one may have a hard time trying to find the service, but the only way to know that is isn't being offered is scan ports looking for it its symptoms. For good reason or bad, there are also all sorts of ways to communicate the location of a service and the port to use that have nothing to do with the DNS and DNS changes, restrictions, and records cannot affect them. These are not special properties of SMTP, with or without MX records; they are properties of TCP. If one wants to fix those problems, then TCP has to be changed to affirmatively return a "no service" message if an attempt is made to connect to a port on which no service is specifically listening. > It was obvious 20+ years ago that MX processing was broken > as there was no way to say "I don't want email". First, it may have been obvious to you, but it wasn't obvious to many of us. In the general case, it still isn't. But you stated the situation exactly correctly. "MX 0 ." means "I don't want email". "SRV 0 0 ." doesn't really indicate "no service", it indicates "please do look for that service here". > Looking > a the MX record, "MX 0 ." was the obvious solution. The > only reason I can see that it never went ahead was FUD. While it is better than interpreting the lack of a bit in a WKS record as "no service", it is still nothing more than an attempt to use the DNS to say "please don't try a mail connection to this domain". I think that is probably ok and would be happy to see a proposal carefully considered to see if consensus could be reached (as Frank points out, there was such a proposal but it quietly disappeared, no FUD campaign needed). But I note that "please don't do X" is a solution to a different set of problems than a solution that would prevent someone who is predisposed to antisocial behavior from trying something. Since bad guys can deduce addresses by scanning --and will certainly do so if we make it sufficiently hard for them to use the DNS-- this type of DNS change, it seems to me, would have little effect on the antisocial. And, again, that isn't a statement about email because it applies with equal force to any other application service we have. > It's so obvious that some MTA's already implement it. Exim > is the example I've been told about. > > The existing MX processing rules assume that *every* host > wants to receive email. The assumption has not been correct > for 20+ years. The existing A processing rules assume that *every* host wants to, or is at least able to, receive web connections, file transfer connections, SIP connections, telnet connections, Jabber connections, and, by the way, DNS connections. Changing the MX rules won't change the assumption that every host supports email. And most, it will make a statement of preference that mail connections won't be accepted more clear. And, viewed in that light, Exim's behavior represents a willingness to honor a preference... a willingness that, incidentally, can be bypassed by the simple expedient of giving it an address in literal form rather than one that is processed via the DNS. Of course, Exim can, and often is, configured to reject mailbox@[ip-literal] addresses, but that behavior is outside the standard. john _______________________________________________ IETF mailing list IETF@ietf.org https://www.ietf.org/mailman/listinfo/ietf
- RE: Last Call: draft-klensin-rfc2821bis (Simple M… Hollenbeck, Scott
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… Pete Resnick
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… Ned Freed
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… Dave Crocker
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… Ned Freed
- Lists and aliases (Re: Last Call: draft-klensin-r… Harald Tveit Alvestrand
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… Pete Resnick
- Re: Lists and aliases (Re: Last Call: draft-klens… Ned Freed
- Re: Lists and aliases (Re: Last Call: draft-klens… Tony Finch
- Re: Lists and aliases (Re: Last Call: draft-klens… Ned Freed
- Last Call: draft-klensin-rfc2821bis (Simple Mail … Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… Ned Freed
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… Ned Freed
- Re: Last Call: draft-klensin-rfc2821bis (Simple M… Pekka Savola
- Re: Last Call: draft-klensin-rfc2821bis Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis Douglas Otis
- Re: Last Call: draft-klensin-rfc2821bis John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis Mark Andrews
- Re: Last Call: draft-klensin-rfc2821bis John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis Douglas Otis
- Re: Last Call: draft-klensin-rfc2821bis John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis John Leslie
- Re: Last Call: draft-klensin-rfc2821bis Ned Freed
- Re: Last Call: draft-klensin-rfc2821bis Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis Douglas Otis
- Re: Last Call: draft-klensin-rfc2821bis Ned Freed
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis Bill Manning
- Re: Last Call: draft-klensin-rfc2821bis Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis Mark Andrews
- Re: Last Call: draft-klensin-rfc2821bis Bill Manning
- Re: Last Call: draft-klensin-rfc2821bis Bill Manning
- Re: Last Call: draft-klensin-rfc2821bis Ned Freed
- Re: Last Call: draft-klensin-rfc2821bis Ned Freed
- Re: Last Call: draft-klensin-rfc2821bis Willie Gillespie
- Re: Last Call: draft-klensin-rfc2821bis Mark Andrews
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis Ned Freed
- Re: Last Call: draft-klensin-rfc2821bis Ned Freed
- Re: Last Call: draft-klensin-rfc2821bis Ned Freed
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis Markku Savela
- Re: Last Call: draft-klensin-rfc2821bis Ned Freed
- RE: Last Call: draft-klensin-rfc2821bis Hallam-Baker, Phillip
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis SM
- Re: Last Call: draft-klensin-rfc2821bis Bill Manning
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis Mark Andrews
- Re: Last Call: draft-klensin-rfc2821bis SM
- Re: Last Call: draft-klensin-rfc2821bis John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis SM
- Re: Last Call: draft-klensin-rfc2821bis Pekka Savola
- Re: Last Call: draft-klensin-rfc2821bis Mark Andrews
- Re: Last Call: draft-klensin-rfc2821bis Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis Bill Manning
- Implicit MX and A RRs (was: Re: Last Call: draft-… John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis Mark Andrews
- Re: Last Call: draft-klensin-rfc2821bis Frank Ellermann
- Re: Implicit MX and A RRs Tony Hansen
- Re: Last Call: draft-klensin-rfc2821bis John Levine
- Re: Last Call: draft-klensin-rfc2821bis Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis Tony Finch
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis John Levine
- Re: Last Call: draft-klensin-rfc2821bis Eliot Lear
- RE: Last Call: draft-klensin-rfc2821bis Tony Hain
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis Dave Crocker
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- RE: Last Call: draft-klensin-rfc2821bis Hallam-Baker, Phillip
- Re: Last Call: draft-klensin-rfc2821bis Willie Gillespie
- IPv6 incentive? RE: Last Call: draft-klensin-rfc2… Hallam-Baker, Phillip
- Re: Last Call: draft-klensin-rfc2821bis Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis Jim Fenton
- Re: Last Call: draft-klensin-rfc2821bis David Conrad
- RE: Last Call: draft-klensin-rfc2821bis Tony Hain
- Re: Last Call: draft-klensin-rfc2821bis Dave Crocker
- Re: Last Call: draft-klensin-rfc2821bis Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- RE: Last Call: draft-klensin-rfc2821bis Hallam-Baker, Phillip
- RE: Last Call: draft-klensin-rfc2821bis Tony Hain
- RE: Last Call: draft-klensin-rfc2821bis John C Klensin
- Re: Implicit MX and A RRs John C Klensin
- Re: Implicit MX and A RRs Matti Aarnio
- RE: Last Call: draft-klensin-rfc2821bis John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis Mark Andrews
- Re: Implicit MX and A RRs Tony Finch
- Re: Last Call: draft-klensin-rfc2821bis Ned Freed
- Re: Last Call: draft-klensin-rfc2821bis Mark Andrews
- Re: Last Call: draft-klensin-rfc2821bis Joe Abley
- Re: Last Call: draft-klensin-rfc2821bis Mark Andrews
- Re: Last Call: draft-klensin-rfc2821bis John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis David Morris
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Implicit MX and A RRs Keith Moore
- RE: Last Call: draft-klensin-rfc2821bis michael.dillon
- Re: Last Call: draft-klensin-rfc2821bis Douglas Otis
- Re: Last Call: draft-klensin-rfc2821bis John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis Ned Freed
- Re: Implicit MX and A RRs Ned Freed
- Re: Last Call: draft-klensin-rfc2821bis Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis Ned Freed
- Re: Last Call: draft-klensin-rfc2821bis Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis Pekka Savola
- Re: Last Call: draft-klensin-rfc2821bis John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis Pekka Savola
- Re: Last Call: draft-klensin-rfc2821bis Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis Ned Freed
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis Dave Crocker
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis Theodore Tso
- Re: Last Call: draft-klensin-rfc2821bis Frank Ellermann
- Re: Last Call: draft-klensin-rfc2821bis Henning Schulzrinne
- Re: Last Call: draft-klensin-rfc2821bis John Levine
- Re: Last Call: draft-klensin-rfc2821bis SM
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis SM
- Re: Last Call: draft-klensin-rfc2821bis John Levine
- Re: Last Call: draft-klensin-rfc2821bis Dave Crocker
- Re: Last Call: draft-klensin-rfc2821bis Henning Schulzrinne
- Re: Last Call: draft-klensin-rfc2821bis David Morris
- Re: Last Call: draft-klensin-rfc2821bis Dave Crocker
- Re: Last Call: draft-klensin-rfc2821bis Mark Andrews
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis John C Klensin
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis Tony Finch
- Re: Last Call: draft-klensin-rfc2821bis Henning Schulzrinne
- Re: Last Call: draft-klensin-rfc2821bis Bill Manning
- Re: Last Call: draft-klensin-rfc2821bis Dave Crocker
- Re: Last Call: draft-klensin-rfc2821bis Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis: closing … Tony Hansen
- Re: Last Call: draft-klensin-rfc2821bis: closing … Dave Crocker
- Re: Last Call: draft-klensin-rfc2821bis: closing … Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis: closing … Lisa Dusseault
- Re: Last Call: draft-klensin-rfc2821bis: closing … Douglas Otis
- Re: Last Call: draft-klensin-rfc2821bis: closing … Hector Santos
- Re: Last Call: draft-klensin-rfc2821bis: closing … Henning Schulzrinne
- Re: Last Call: draft-klensin-rfc2821bis: closing … Dave Crocker
- Re: Last Call: draft-klensin-rfc2821bis: closing … Paul Smith
- Re: Last Call: draft-klensin-rfc2821bis: closing … Keith Moore
- Re: Last Call: draft-klensin-rfc2821bis: closing … Tom.Petch
- Re: Last Call: draft-klensin-rfc2821bis: closing … Hector Santos
- Re: Last Call: draft-klensin-rfc2821bis: closing … Robert A. Rosenberg