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Re: axfr-clarify on the move again
At 9:14 +0000 11/24/02, D. J. Bernstein wrote:
RFC 1034 and RFC 1035 make crystal clear that record sets in the Domain
Name System at any moment are indexed by class+name+type. Nothing else.
RFC 2181, Section 5.4.1., defines a differentiation between two RR
sets matching the same {QNAME, QTYPE, QCLASS}.
1. Consider, once again, client differentiation, or ``views'' in BIND
9: some servers store data by class+name+type+clientIP. Everybody
else is free to assume that this doesn't happen. For example, a
cache that uses two IP addresses for its outgoing requests, and
receives different data under the same class+name+type on the two
IP addresses, is under absolutely no obligation to keep track of
both record sets.
An implementation choice, not part of the DNS protocol.
2. Consider, as a simpler example, the fact that different servers
for a zone can have different data. Everybody else is free to
assume that this doesn't happen. If I receive different record
sets from the two servers, under the same class+name+type, I can
use either one. I'm under no obligation to keep track of both
record sets.
RFC 2181, Section 5.4.1.
3. Finally, getting back to the situation under discussion: It's
certainly possible for a parent and a child to have different data
for the same class+name+type. But everybody else is free to assume
that this doesn't happen. If I receive different record sets from
the two servers, under the same class+name+type, I can use either
one. I'm under no obligation to keep track of both record sets.
RFC 2181, Section 5.4.1.
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Edward Lewis +1-703-227-9854
ARIN Research Engineer
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