Re: [mif] Domain name issue in draft-stenberg-mif-mpvd-dns

Markus Stenberg <markus.stenberg@iki.fi> Tue, 15 March 2016 11:35 UTC

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From: Markus Stenberg <markus.stenberg@iki.fi>
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Date: Tue, 15 Mar 2016 13:35:45 +0200
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References: <56E7E35D.6040108@bellis.me.uk> <2514F81A-CDC6-4F90-A76D-816A8F4EEDC4@iki.fi> <56E7F060.1040004@bellis.me.uk>
To: Ray Bellis <ray@bellis.me.uk>
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Cc: draft-stenberg-mif-mpvd-dns@ietf.org, mif@ietf.org
Subject: Re: [mif] Domain name issue in draft-stenberg-mif-mpvd-dns
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> On 15.3.2016, at 13.22, Ray Bellis <ray@bellis.me.uk>; wrote:
> On 15/03/2016 11:08, Markus Stenberg wrote:
>> Actually we considered it a feature and not a bug, i.e. subdelegation
>> would still result in same PVD available. I am not sure your scheme
>> would work with subdelegation though.
> OK, I see that, but I still think you have a problem since:
> 
>   2001:0:0:0::/64
> 
> and
> 
>   2001:0:0:0:0::/80
> 
> and even:
> 
>   2001::/16
> 
> will end up at the same domain name.

Not necessarily. Your home _could_ provide (split horizon) different records than someone else's home. Or ISP could subdelegate that part to your home (then again, I am not sure I would bet on it).

>> Given broad example, ISP has /40 for home users, but ultimately the
>> prefix in use may be e.g. /64 (or even something more narrow). Having
>> the _pvd.* in 'all' prefix lengths would be obviously available, or
>> performing (up to 128) lookups with subsequently shorter/longer
>> prefix lengths.
>> 
>> I am not sure how client would know to start lookups from /40, or
>> from /56 assigned to a home, if the link has /64.
> In RFC 7216 we took a "minimal" tree climbing approach, putting the
> records at "common" LIR / RIR prefix boundaries of /64, /56, /48, or
> /32.   Anything more would have angered the DNS Gods...
> 
> Is there no other way for the client to learn the size of the upstream
> PD from which its /64 has been carved out?

Not without some new option in RA/DHCP I think.

Cheers,

-Markus