[dns-operations] should recursors think there are only delegation data in tld name servers?

[Stephane Bortzmeyer]

On Wed, Mar 26, 2014 at 08:22:03PM +0800,
 刘明星 <lmxhappy at gmail.com> wrote 
 a message of 59 lines which said:

> if a recursor ask a tld server for A records of a domain name,
> such as a.test.tld, the .tld server return a nxdomain response to
> the recursor.

Only if test.tld does not exist.

> In this case, the recusor does not know whether there are other
> domain names related to test.tld, like b.a.test.tld,

That's not true. If the TLD server returned NXDOMAIN for the query
a.test.tld, the recursor can be sure b.a.test.tld does not exist either.

> b.test.cn and c.b.test.cn, 

[I assume you mean b.test.tld and c.b.test.tld]

It is a bit more complicated because it depends whether the TLD server
is also authoritative for test.tld or not.