Recursive DNS problem

[Torinthiel]

Dnia 2011-01-28 10:52 bangla desh napisał(a):


>> I believed so that com.bd is broken. It only has 1 ns server and
>hsbc.com.bd, whois.com.bd and even google.com.bd they are all delegate
>directly from bd and not from com.bd.
>
>I am wondering, is there a dns rule/standard (or RFC) that explains about
>delegation?

For the fact that com.bd is broken - that's just how DNS works. Zone cuts 
are there for purpose. Most of this can be read from RFC 1034 and 1035, 
which form the grounds for DNS standards. Also RFC 2181 clarifies:
<quote>
A server for a zone should not return authoritative answers for queries 
related to
   names in another zone, which includes the NS, and perhaps A, records
   at a zone cut, unless it also happens to be a server for the other
   zone.
</quote>
And a mere presence of NS records indicates a zone cut (again, RFC 2181):
<quote>
The existence of a zone cut is indicated in the parent zone by the
   existence of NS records specifying the origin of the child zone.
</quote>

As for number of authorative servers per domain, I don't remember where, but 
at leas one RFC stated that there should be at least two, and preferably 3-7 
nameservers per domain. It's quite possible that one of those I've already 
pointed to contains this information, but also that a different one states 
this information. But it was RFC for certain.
Regards,
 Torinthiel