Re: [DNSOP] I-D Action: draft-ietf-dnsop-edns-client-subnet-07.txt

[神明達哉 <[e-mail]>]

At Mon, 21 Mar 2016 19:21:59 +0530,
Mukund Sivaraman <[e-mail]> wrote:

> (1) Section 7.2.1.  Authoritative Nameserver:
>
> > When deaggregating to correct the overlap, prefix lengths should be
> > optimized to use the minimum necessary to cover the address space, in
> > order to reduce the overhead that results from having multipe copies
> > of the same answer.  As a trivial example, if the Tailored Response
> > for 1.2.0/20 is A but there is one exception of 1.2.3/24 for B, then
> > the Authoritative Nameserver would need to provide Tailored Responses
> > for 1.2.0/23, 1.2.2/24, 1.2.4/22, and 1.2.8/21 all pointing to A, and
> > 1.2.3/24 to B.

I'm confused about the revised Section 7.2.1 regarding overlapping
prefixes.  The 07 version of the draft now states:

   [...]  Because it can't be guaranteed that queries for all
   longer prefix lengths would arrive before one that would be answered
   by the shorter prefix length, an Authoritative Nameserver MUST NOT
   overlap prefixes.

But the above "trivial example" seems to talk about what an
authoritative nameserver would do if it overlaps prefix...doesn't it
simply break the MUST NOT in the first place?

Also (ignoring the MUST NOT), what if a query is sent with a source
prefix 1.2.1/24?  The best matching prefix is 1.2.0/20, so isn't the
tailored response A with the scope prefix length of 20?  I mean,
shouldn't the above deaggregated prefixes be incomplete?

--
JINMEI, Tatuya