Usage of NS records as part of query response

[Alexis S. <al...@pi...>]

I've recently investigated a problem involving dnsjava, DNS servers operated
my ISP and a DNS server I own. 
 
The problem can be summarized as follows: 
 
Record[] r = new Lookup("a.domain.com", Type.A).run(); 
// r is not NULL 
r = new Lookup("b.domain.com", Type.A).run(); 
// r is NULL 
// Lookup returns error code TIME OUT 
 
here, both DNS names (a and b) are actually present in DNS. 
 
 
The problem appear to be related to the way dnsjava interprets the first
(successful) response. My ISP's DNS server returned not only A record, but
also NS record ("ns.domain.com") as part of the response. 
 
The second run of Lookup attempts to resove "ns.domain.com" before trying to
recolve "b.domain.com". 
 
It turns out, I forgot to provide A record for "ns.domain.com" as part of my
zone file for domain.com. Fixing the zone file fixes the problem above, but
begs 2 questions:  
Why do some DNS servers send NS records as part of the response?  
Why does dnsjava attemts to resolve NS names? 
 
Thanks! 
Alexis Smirnov
http://weblog.smirnov.ca <http://weblog.smirnov.ca/> 

 

PS: i'm not monitoring this forum so i'd appreciate receiving a CC for any
response.