Re: [dnsext] Some thoughts on the updated aliasing draft

"John R. Levine" <> Mon, 28 March 2011 02:48 UTC

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Date: Sun, 27 Mar 2011 22:50:10 -0400
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From: "John R. Levine" <>
To: Mark Andrews <>
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Subject: Re: [dnsext] Some thoughts on the updated aliasing draft
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> And SMTP had it correct for the second group.  If the SMTP client
> sees the CNAME it re-writes the names in the SMTP exchange to use
> the cannonical host name.  The SMTP server never see the alias.

Yes and no.  That works OK if you expect the CNAME to be a nickname for 
the real name, and the user is happy to see his message headers rewriten 
to use the canonical name.  It fails in the situation where the names are 
all equivalent, and you don't want the messages rewritten.

It also doesn't address the security issue, if you want the owner of the 
canoninical name to have control over what can be aliased to it.

> HTTP administrators often misuse CNAME.

True, but the horse is dead, and the carcass was long ago sold for 
dogfood, so I don't see the point of dredging it up again.

John Levine,, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail.