Re: [DNSOP] ANAME precedence [issue #58]

[Matthijs Mekking <[e-mail]>]

On 4/25/19 8:34 PM, 神明達哉 wrote:
> At Wed, 24 Apr 2019 11:44:37 +0200,
> Matthijs Mekking <[e-mail]
> <mailto:[e-mail]>> wrote:
> 
>> I would like to start separate threads on the remaining issues of the
>> ANAME draft. One issue that remains to be solved is whether having an A
>> or AAAA record next to the ANAME should take precedence or not.
>>
>>   Draft: https://datatracker.ietf.org/doc/draft-ietf-dnsop-aname/
>>   Issue: https://github.com/each/draft-aname/issues/58
> [...]
>> Jan Včelák mentioned that at least NS1 uses a different order of
>> priority: If an sibling address record exists next to the ANAME it takes
>> precedence and no target lookup is done for that address record type.
> 
> Is this choice #2 of the github issue #58?

Correct.


>>> sibling address records take precedence, don't to a target lookup for
> an address type next to the ANAME.
> 
> I'm not sure what this means...if this approach is taken and an
> authoritative server has these for an example.com <http://example.com> zone:
> 
> a.example.com <http://a.example.com>. ANAME another.example.org
> <http://another.example.org>.
> a.example.com <http://a.example.com>. AAAA 2001:db8::1
> 
> then, does it always just return the AAAA RRset to a query for
> a.example.com/AAAA <http://a.example.com/AAAA>, regardless of any
> possible changes to
> another.example.org/AAAA <http://another.example.org/AAAA>?

That is exactly what choice #2 does. But it can do a target lookup for
the A RRset.


> How is that AAAA created in the first place?  (Is it taken from
> another.example.org/AAAA <http://another.example.org/AAAA> or completely
> up to the example.com <http://example.com>
> maintainer?)..

The AAAA record may initially be added to the example.com zone by the
zone operator. With choice #2 it is not updated by the ANAME (with
choice #1 it is).


> Also, especially if both AAAA and A sibling records are available,
> what's the purpose of ANAME in the first place if it's (effectively)
> not used?
> 
> I'm sure I'm just confused and don't understand the expected usage,
> but I can't figure it out from the available descriptions.  Could you
> clarify it?

Personally I agree that the purpose of ANAME becomes less useful with
choice #2.  The difference is that you can set up ANAME for example for
AAAA only, or for A only. I don't know what the expected usage of that
is, and that is why I am asking on the list. If it turns out there is no
useful case, I think we should put text in the draft that says ANAME
takes precedence over sibling A and AAAA records.


Best regards,

Matthijs



> 
> --
> JINMEI, Tatuya
> 
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