Re: [dnsext] I-D Action:draft-ietf-dnsext-aliasing-requirements-00.txt

[Tony Finch <[e-mail]>]

On Tue, 1 Mar 2011, Phillip Hallam-Baker wrote:
>
> 2) The Server performs the rewrite.
>
> This is really hard to achieve as it requires the server to know that
> the mapping even exists.
>
> Typically a server is responding to hundreds of domains. Even large
> production servers do this. If a server receives a request for a.com
> it has no means of knowing that it 'should' map that to b.com unless
> the DNS configuration is somehow mapped to the Web administration.
>
> This is quite straightforward to handle administratively when the
> mapping is www.b.com to b.com because the source and target are in the
> same administrative zone. But this is not going to work if the mapping
> is being controlled by a TLD.

On the contrary, this is trivial for the server to do by dynamically
looking up a.com and seeing if it is a BNAME pointing at b.com.

However the server administrator probably does not want the server to
accept requests for arbitrary domains just because they have a BNAME
pointer.

So there has to be a list of valid aliases somewhere accessible to the
server, either in the DNS for b.com (used like "paranoid" reverse DNS
checking) or in the server's configuration.

Given the existence of HTTP redirects, I'm not entirely sure that it is
reasonable to forbid DNS aliasing. But server administrators are free to
choose between loose dynamic configurations and tight explicit
configurations without affecting clients.

The question for this group is if we specify something like BNAME if we
should also specify how to put the corresponding back-references in the
canonical domain.

Tony.
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