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Re: [DNSOP] DNSKEY Flags vs. CDS/CDNSKEY

Olafur Gudmundsson <ogud@ogud.com> Fri, 07 February 2014 23:46 UTC

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From: Olafur Gudmundsson <ogud@ogud.com>
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Date: Fri, 07 Feb 2014 18:46:05 -0500
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To: Mukund Sivaraman <muks@isc.org>
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Subject: Re: [DNSOP] DNSKEY Flags vs. CDS/CDNSKEY
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On Feb 7, 2014, at 1:31 PM, Mukund Sivaraman <muks@isc.org> wrote:

> Hi Warren
> 
> Did you see my reply to your email a few weeks ago where I asked why new
> CDS/CDNSKEY RR types are required instead of adding a new bit to the
> Flags field of the DNSKEY RR. Please can you look for my last email
> which lists some advantages? There may be a good reason for it, but I
> don't want you to miss considering it. :)
> 

We considered it but there are drawbacks including:
- changing a flag on a DNSKEY record means the key footprint and hash of key change, so matching 
  a key after a change in flags is hard for parents as they do not know which flag was changed. 
- Publishing a future TA in the DNSKEY set makes the DNSKEY RRset larger 

There are advantages to the new RR types 
- CDS allows the publication of a new Trust Anchor without exposing the public key of the new trust anchor 
- Putting a new key in a different RRset keeps DNSKEY smaller 
- less chance of confusion by parents. 

So in short we considered it and rejected that approach. 

	Olafur

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