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

["John Levine" <[e-mail]>]

>if we're allowed by the people asking for this to require dns client
>libraries and applications to have to be changed to handle a new kind
>of canonicalization before they'll be able to handle the new
>definition of "sameness" then this is a practical approach.

It seems to me that we can divide applications into two groups.  In one
group, the client uses the name to find a server, but the name never
appears in the data stream or only appears as a comment.  This includes
FTP, SSH, POP, and IMAP.  Something like BNAME would be adequate to make
names look the same to users.  I'd say these applications don't know
what their names are.

In the other group, the domain name appears in the data stream, and
the server does something with it beyond resolving it to an A or AAAA
record.  The standard examples are SMTP and HTTP.  These apps do know
what their names are, and the only alternatives I see are a great deal
of manual provisioning, or else they learn how to check the DNS to see
whether a hitherto unknown name in the data stream is an alias of a
canonical name that it does know.  So, yeah, the applications will
eventually have to change.

>From the point of view of DNS design, I'd want something that returns
an appropriate A or AAAA for the first group, and offers a
straightforward way for the second group to see what's an alias of
what.

For a transition, it's still possible to configure the second group
manually, but it'd be a lot easier if they got smarter so people
didn't have to do so.

R's,
John