Re: [DNSOP] Extended CNAME (ENAME)
Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp> Fri, 23 May 2014 05:25 UTC
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Date: Fri, 23 May 2014 14:25:23 +0900
From: Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp>
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To: Tony Finch <dot@dotat.at>, dnsop@ietf.org
References: <20140517010406.CD30615FE072@rock.dv.isc.org> <20140518163140.GB27592@solar.andreasschulze.de> <20140518223911.308F4160674D@rock.dv.isc.org> <537C15B4.2000008@necom830.hpcl.titech.ac.jp> <20140521031102.A1CDD1632244@rock.dv.isc.org> <537C24FA.6020804@necom830.hpcl.titech.ac.jp> <alpine.LSU.2.00.1405211221580.16298@hermes-1.csi.cam.ac.uk> <537C927F.3020007@necom830.hpcl.titech.ac.jp> <alpine.LSU.2.00.1405211251150.16298@hermes-1.csi.cam.ac.uk> <537D5AB5.1090101@necom830.hpcl.titech.ac.jp> <alpine.LSU.2.00.1405221021510.16298@hermes-1.csi.cam.ac.uk>
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Subject: Re: [DNSOP] Extended CNAME (ENAME)
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Tony Finch wrote: >> Perhaps, it is a misunderstanding of a suggestion of rfc974: >> >> Note that the algorithm to delete irrelevant RRs breaks if LOCAL has >> a alias and the alias is listed in the MX records for REMOTE. (E.g. >> REMOTE has an MX of ALIAS, where ALIAS has a CNAME of LOCAL). This >> can be avoided if aliases are never used in the data section of MX >> RRs. > > No, that's about MX pointing at CNAME, > CNAME pointing at MX is a different problem, There is an interesting history of confusion. See below. > The requirement in RFC 1123 is a restatement of > RFC 821 section 3.7 (last paragraph) and page 30 (penultimte paragraph). At that time, there was no MX-like mechanism in domain names and rfc819 discusess domain->address mapping only. A mail to a domain is delivered to domain's address. As such, rfc974 specifies: It is possible that the list of MXs in the response to the query will be empty. This is a special case. If the list is empty, mailers should treat it as if it contained one RR, an MX RR with a preference value of 0, and a host name of REMOTE. (I.e., REMOTE is its only MX). Thus, what rfc821 prohibits is alias->address, CNAME pointing to A, with an obvious reason to prevent mail loops, if mail software is not robust enough not to be able to recognize its identity involving aliases. With introduction of MX, what should have been prohibited is still CNAME pointing to A, that is, MX pointing to CNAME then to A (as rfc974 mentions), not CNAME pointing to MX (rfc1123). Masataka Ohta
- [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Mark Delany
- Re: [DNSOP] Extended CNAME (ENAME) Paul Vixie
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Ted Lemon
- Re: [DNSOP] Extended CNAME (ENAME) Joe Abley
- Re: [DNSOP] Extended CNAME (ENAME) Ted Lemon
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Måns Nilsson
- Re: [DNSOP] Extended CNAME (ENAME) Patrik Fältström
- Re: [DNSOP] Extended CNAME (ENAME) Tim Wicinski
- Re: [DNSOP] Extended CNAME (ENAME) Andreas Schulze
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Jelte Jansen
- Re: [DNSOP] Extended CNAME (ENAME) John Levine
- Re: [DNSOP] Extended CNAME (ENAME) Paul Hoffman
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Paul Vixie
- Re: [DNSOP] Extended CNAME (ENAME) David C Lawrence
- Re: [DNSOP] Extended CNAME (ENAME) Ted Lemon
- Re: [DNSOP] Extended CNAME (ENAME) Bob Halley
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Bob Halley
- Re: [DNSOP] Extended CNAME (ENAME) Paul Hoffman
- Re: [DNSOP] Extended CNAME (ENAME) Ted Lemon
- Re: [DNSOP] Extended CNAME (ENAME) Ted Lemon
- Re: [DNSOP] Extended CNAME (ENAME) Olafur Gudmundsson
- Re: [DNSOP] Extended CNAME (ENAME) Andrew Sullivan
- Re: [DNSOP] Extended CNAME (ENAME) Paul Vixie
- Re: [DNSOP] Extended CNAME (ENAME) Patrik Fältström
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Jelte Jansen
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Ben Laurie
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Chris Thompson
- Re: [DNSOP] Extended CNAME (ENAME) Petr Spacek
- Re: [DNSOP] Extended CNAME (ENAME) Tony Finch
- Re: [DNSOP] Extended CNAME (ENAME) Patrik Fältström
- Re: [DNSOP] Extended CNAME (ENAME) Ted Lemon
- Re: [DNSOP] Extended CNAME (ENAME) Ted Lemon
- Re: [DNSOP] Extended CNAME (ENAME) Ted Lemon
- Re: [DNSOP] Extended CNAME (ENAME) Patrik Fältström
- Re: [DNSOP] Extended CNAME (ENAME) Ted Lemon
- Re: [DNSOP] Extended CNAME (ENAME) Jakob Schlyter
- Re: [DNSOP] Extended CNAME (ENAME) Mark Delany
- Re: [DNSOP] Extended CNAME (ENAME) Paul Vixie
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Paul Vixie
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Patrik Fältström
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Klaus Malorny
- Re: [DNSOP] Extended CNAME (ENAME) Ralf Weber
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Saku Ytti
- Re: [DNSOP] Extended CNAME (ENAME) Klaus Malorny
- Re: [DNSOP] Extended CNAME (ENAME) Klaus Malorny
- Re: [DNSOP] Extended CNAME (ENAME) Tony Finch
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Tony Finch
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Tony Finch
- Re: [DNSOP] Extended CNAME (ENAME) Saku Ytti
- Re: [DNSOP] Extended CNAME (ENAME) Klaus Malorny
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Andrew Sullivan
- Re: [DNSOP] Extended CNAME (ENAME) Dan York
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) John Levine
- Re: [DNSOP] Extended CNAME (ENAME) Ralf Weber
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) S Moonesamy
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Mark Andrews
- Re: [DNSOP] Extended CNAME (ENAME) Tony Finch
- Re: [DNSOP] Extended CNAME (ENAME) Klaus Malorny
- Re: [DNSOP] Extended CNAME (ENAME) Tony Finch
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Masataka Ohta
- Re: [DNSOP] Extended CNAME (ENAME) Ray Bellis
- Re: [DNSOP] Extended CNAME (ENAME) Saku Ytti
- Re: [DNSOP] Extended CNAME (ENAME) Ted Lemon
- Re: [DNSOP] Extended CNAME (ENAME) Joe Abley
- Re: [DNSOP] Extended CNAME (ENAME) Andrew Sullivan
- Re: [DNSOP] Extended CNAME (ENAME) Tim Wicinski
- Re: [DNSOP] Extended CNAME (ENAME) John Levine
- Re: [DNSOP] Extended CNAME (ENAME) Ray Bellis
- Re: [DNSOP] Extended CNAME (ENAME) Florian Weimer
- Re: [DNSOP] Extended CNAME (ENAME) Andrew Sullivan