Q: Delegated Servers vs NS records used in queries?

[Roy Arends]

On Fri, 7 Sep 2001, David Connors wrote:

> Hi,
>
> I have a question.
>
> Consider the following:
> 1. Suppose you have a domain xyz.com.
> 2. xyz.com is delegated to ns1.xyz.com and ns2.xyz.com.
> 3. the xyz.com zone file contains THREE NS records for ns1.xyz.com,
> ns2.xyz.com, and an additional server, ns3.xyz.com.
>
> When a client on the other side of the world attempts to query xyz.com, will
> there ever be a scenario where ns3.xyz.com will be queried?  In otherwords,
> is it part of the DNS standard that ONLY the delegated servers are queried?
> Or is it that after the NS records are retrieved, a client DNS server might
> consider any NS record as fair game for a subsequent query?

A recursive nameserver will follow initially the delegation NS records
(the NS records at .com). After it receives an authoritative answer from
ns[12].xyz.com, it will cache its accompanying authoritative and
additional sections. Since those sections contain all 3 authoritative
nameservers, those 3 will subsequently be queried within the TTL of the
cached record.

Regards,

Roy Arends
Nominum
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0-14-023750-X dcrpt ths 43.0D.01 01.05.0C 84.18.03 8A.13.04 2D.0B.0A