[DNSOP] Potential root impact of draft-wing-behave-learn-prefix-00

[Florian Weimer <fw at deneb.enyo.de>]

I came across the following in some IPv6-related draft and thought I'd
share it.

|3.1.  Using DNS to Learn IPv6 Prefix and Length
|
|   In order for an IPv6 host to determine if a NAT64 is present on its
|   network, it sends a DNS query.  Because a host doesn't always know
|   its network's default domain name, the procedure described below
|   provides a way for the host to learn it in order to authorize that
|   network's address family translator:
|
|   1.  Send a DNS AAAA query for "_aft_prefix", without a domain name.
|       If this does not return an IPv6 address it means a address family
|       translator is not present and processing MUST stop.

[...]

|   3.  If validation of this information is not necessary, then:
|
|       a.  Send a DNS TXT query for "_aft_prefix", without the domain
|           name, to learn the number of bits of the prefix.
|

[...]

|      Discussion:  without a domain name, it is unavoidable that root
|      nameservers will see this query.  Need to think about ways to
|      reduce the effect of those queries (e.g., make them authoritative
|      and return all 0's which will get cached).

So they are aware that this is broken.  Let's hope that this type of
service discovery through a fraction DNS root doesn't make its way
into the final standard.
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