Bind 9 truncating responses

[David Botham]

bind-users-bounce at isc.org wrote on 04/22/2005 05:28:03 AM:
> Can anybody comment?
> 
> First things first: I understand that 50 NS records in a zone are not 
good 
> practice however situations require that this be the case.
> 
> I have been completing some testing where I have approx 50 NS records 
within a
> zone.  When I place this zone on a Bind 9 Server and query for an A 
record in 
> this zone from nslookup Bind places the answer in the answer section 
> correctly.  It then jams as many NS and Glue records in the additional 
and 
> authority section as possible.  As not all of the NS and Glue records 
fitted 
> in the packet the Bind 9 Server sets the TC bit in the DNS header.  This 
same 
> test on Bind 8 shows different behaviour as Bind 8 does not set the TC 
bit.
> 
> Should Bind 9 be doing this as it supplied the answer?  Setting the TC 
would 
> cause most implementations to retry the query via TCP causing more work 
for 
> the Server and using up a TCP resource.
> 
> Are the NS and A records considered required/important for the response 
to an 
> A record query?

BIND 9 will put all of the RR's in the response.  Because they will not 
all fit it truncates the response.  This behavior is correct.  I suggest 
using less NS RR's in your NS RR Set.  For a second level domain somewhere 
in the range of 8 NS RR's should avoid the truncation.


Dave...


> 
> Cheers
> 
> 
>