A clarification of RFC2182 Listed Server

[Barry Margolin]

In article <0C847D07445BD311B8F300104B30A0D9014670 at aristotle.lyceum.com>,
Jim Howard  <howardj at psi.net> wrote:
>> -----Original Message-----
>> From: Ray Buschur [mailto:rbuschur at mailsrv2.mitre.org]
>> Sent: Monday, May 01, 2000 3:27 PM
> 
>> I am reviewing several RFCs related to DNS and DNS policies 
>> and practices.
>> While reading RFC 2182, I came across the term "listed 
>> server".  My question
>
>> A.  the servers identified on the delegation NS records in 
>> the parent zone
>> 
>> B.  the servers identified as announced secondary NS records 
>> inside the zone
>> itself
>> 
>> C.  All the servers in both A & B above
>
>I believe that the use of the term here means "B",
>but understand that while it is valid to have servers in
>group "B" that are not in group "A", you should not have 
>servers in group "A" that are not in group "B".
>(thus group "C" should equal group "B" anyway.)

Could you explain why A has to be a subset of B?  Over the course of the
past year we've been phasing over from one set of DNS servers to another
set, call them OLDDNS and NEWDNS.  Our automated configuration scripts
ensure that any domain that's configured on OLDDNS is also configured on
NEWDNS, and we've been working with NSI to have them update the delegation
records to replace OLDDNS (this is being done in two phases: first they
added NEWDNS to any domains that mentioned OLDDNS, and now they're in the
process of removing OLDDNS).  Our plan is that when this is all done, we'll
replace the OLDDNS A record with one that points to the same address as
NEWDNS.  The point of this is that we don't want to make all our customers
that we do secondary DNS for have to update the NS records in their zones
right away.

Anyway, the upshot of this is that there are lots of domains where set A is
OLDDNS+NEWDNS or just NEWDNS, while set B is just OLDDNS or NEWDNS (sets A
and B also usually include the customer's primary server, but that's
immaterial to this discussion).  The servers that are actually
authoritative is set C, and I think that's the important thing -- whichever
set someone has cached will work.

-- 
Barry Margolin, barmar at genuity.net
Genuity, Burlington, MA
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