To:
dnsop@cafax.se
From:
"D. J. Bernstein" <djb@cr.yp.to>
Date:
16 Jul 2003 06:09:31 -0000
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Subject:
Re: regarding the respsize draft: preferring glue of certain types
Randy Bush writes:
> this assumes that the transport available between the dns resolver and
> the dns server is correlated to the transport between the application
> client and the server.
No. The issue is delegations, particularly big delegations such as the
DNS root servers' delegation of .com to 13 different DNS servers. Both
levels are DNS; there isn't any ``application client'' here.
Suppose that a .com DNS server has both A and AAAA. I don't see why the
root servers would ever want to provide both addresses. Specifically:
* If the query shows up through IPv4, why bother sending the .com
server's AAAA address? Obviously the resolver is capable of
reaching the A address.
* If the query shows up through IPv6, why bother sending the .com
server's A address? Obviously the resolver is capable of reaching
the AAAA address.
Vixie was suggesting omitting AAAA's past the 512-byte limit in the
first case, and A's past the 512-byte limit in the second, but I don't
see any use of the extra records even if they all fit into 512 bytes.
---D. J. Bernstein, Associate Professor, Department of Mathematics,
Statistics, and Computer Science, University of Illinois at Chicago
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