Bind 9 truncating responses
Stephen Vickers
stephen at n3k.co.uk
Fri Apr 22 07:42:45 UTC 2005
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?
Cheers
----------
Stephen Vickers
Technical Support
n3k Informatik Limited
The Square
Basing View
Basingstoke
RG21 4EB
Email: support at n3k.co.uk
Tel: 012 5630 3700
Fax: 012 5630 3701
Support: 012 5630 3777
Web: www.n3k.co.uk
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