Re: [Asrg] DNS basics, was overloading server names doesn't work
"John R Levine" <johnl@taugh.com> Tue, 09 February 2010 19:04 UTC
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From: John R Levine <johnl@taugh.com>
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Cc: Anti-Spam Research Group - IRTF <asrg@irtf.org>
Subject: Re: [Asrg] DNS basics, was overloading server names doesn't work
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>>>>>> Nope, that won't work. CNAMEs don't do a partial match. >> >>> Where did I or anyone else specify a partial match? >> >> The user thinks his POP server is called mail.btinternet.com. When he >> looks up _report.mail.btinternet.com, what do you expect to happen? > > He'll get a TXT record back. This is nothing but exactly the same mechanism > that is used for DKIM and SRV, albeit with a different underscore subdomain. > > The DNS construct of partial matching has nothing to do with this mechanism. Sorry, that's just plain wrong, he'll get NXDOMAIN. You're expecting CNAMEs to do things that they don't do. Don't take my word for it -- you know all the old DNS weenies better than I do so ask them. Or see RFC1034, section 3.6.2 on page 14, and the algorithm in 4.3.2 on page 24, in particular step 3.a. It wasn't a problem for DKIM because it's exceedingly rare and somewhat disreputable to use a CNAME to to point to an MX, but as we've seen it's very common for the A record for POP and IMAP servers. R's, John PS: We'll save the other reasons CNAMEs don't do what you want for the advanced seminar.
- [Asrg] Iteration #3. Chris Lewis
- Re: [Asrg] Iteration #3. Dave CROCKER
- Re: [Asrg] Iteration #3. Steve Atkins
- Re: [Asrg] Iteration #3. Chris Lewis
- Re: [Asrg] Iteration #3. Derek Diget
- Re: [Asrg] Iteration #3. Alessandro Vesely
- Re: [Asrg] Iteration #3. Chris Lewis
- Re: [Asrg] Iteration #3. Chris Lewis
- [Asrg] Consensus Call - submission via posting (w… Dave CROCKER
- Re: [Asrg] Consensus Call - submission via postin… Lyndon Nerenberg (VE6BBM/VE7TFX)
- Re: [Asrg] Consensus Call - submission via postin… Chris Lewis
- Re: [Asrg] Consensus Call - submission via postin… Steve Atkins
- Re: [Asrg] Consensus Call - submission via postin… Dave CROCKER
- Re: [Asrg] Consensus Call - submission via postin… Dotzero
- Re: [Asrg] Iteration #3. Derek Diget
- Re: [Asrg] Consensus Call - submission via postin… Derek Diget
- Re: [Asrg] Consensus Call - submission via postin… Bart Schaefer
- Re: [Asrg] Consensus Call - submission via postin… Alessandro Vesely
- Re: [Asrg] Iteration #3. Alessandro Vesely
- Re: [Asrg] Iteration #3. Daniel Feenberg
- Re: [Asrg] Iteration #3. John Levine
- Re: [Asrg] Iteration #3. Daniel Feenberg
- Re: [Asrg] Iteration #3. Dave CROCKER
- Re: [Asrg] Iteration #3. John Levine
- Re: [Asrg] Iteration #3. Dave CROCKER
- Re: [Asrg] Consensus Call - submission via postin… Ian Eiloart
- Re: [Asrg] Consensus Call - submission via postin… John Levine
- Re: [Asrg] Consensus Call - submission via postin… BOBOTEK, ALEX (ATTCINW)
- Re: [Asrg] Consensus Call - submission via postin… Andrew Richards
- [Asrg] who has the message (was Re: Consensus Cal… Dave CROCKER
- Re: [Asrg] Consensus Call - submission via postin… Chris Lewis
- Re: [Asrg] Consensus Call - submission via postin… Andrew Richards
- Re: [Asrg] who has the message (was Re: Consensus… Andrew Richards
- Re: [Asrg] who has the message (was Re: Consensus… Dave CROCKER
- Re: [Asrg] who has the message (was Re: Consensus… Chris Lewis
- Re: [Asrg] who has the message (was Re: Consensus… John Levine
- Re: [Asrg] who has the message (was Re: Consensus… Dave CROCKER
- Re: [Asrg] overloading server names doesn't work,… John R Levine
- Re: [Asrg] Consensus Call - submission via postin… Bill Cole
- Re: [Asrg] overloading server names doesn't work,… Daniel Feenberg
- Re: [Asrg] who has the message (was Re: Consensus… Ian Eiloart
- Re: [Asrg] Consensus Call - submission via postin… Ian Eiloart
- Re: [Asrg] who has the message (was Re: Consensus… Ian Eiloart
- Re: [Asrg] who has the message (was Re: Consensus… Andrew Richards
- Re: [Asrg] who has the message (was Re: Consensus… Andrew Richards
- Re: [Asrg] who has the message (was Re: Consensus… Ian Eiloart
- Re: [Asrg] who has the message (was Re: Consensus… Andrew Richards
- Re: [Asrg] who has the message (was Re: Consensus… Ian Eiloart
- Re: [Asrg] overloading server names doesn't work,… Dave CROCKER
- Re: [Asrg] who has the message (was Re: Consensus… Paul Russell
- Re: [Asrg] overloading server names doesn't work,… John R Levine
- Re: [Asrg] overloading server names doesn't work,… Dave CROCKER
- Re: [Asrg] DNS basics, was overloading server nam… John R Levine
- Re: [Asrg] Consensus Call - submission via postin… Andrew Richards
- Re: [Asrg] Consensus Call - submission via postin… Ian Eiloart
- Re: [Asrg] DNS basics, was overloading server nam… Dave CROCKER
- Re: [Asrg] DNS basics, was overloading server nam… John R Levine
- Re: [Asrg] Consensus Call - submission via postin… Jose-Marcio Martins da Cruz
- Re: [Asrg] DNS basics, was overloading server nam… Douglas Otis
- Re: [Asrg] Consensus Call - submission via postin… Ian Eiloart
- Re: [Asrg] Consensus Call - submission via postin… Jose-Marcio Martins da Cruz