Subject: [Question] RRSet should only be included once in any DNS reply

From: Hideshi Enokihara <[email-masked]>
Date: Wed, 21 Dec 2005 19:08:22 +0900

Hi all,

I have a question regarding the following RFC's description. 

---------------------
5.5. Sending RRSets (reprise)

   A Resource Record Set should only be included once in any DNS reply.
   It may occur in any of the Answer, Authority, or Additional
   Information sections, as required.  However it should not be repeated
   in the same, or any other, section, except where explicitly required
   by a specification.  For example, an AXFR response requires the SOA
   record (always an RRSet containing a single RR) be both the first and
   last record of the reply.  Where duplicates are required this way,
   the TTL transmitted in each case must be the same.
----------------------

Does this description suggest that it is called "RRset" even if one RR included in answer?
If so, following example responses should be like "Correct Answer1" and "Correct Answer2"

-------example 1----------- 
Question section
	QNAME = NS.example.org
	QTYPE = A
ANSWER section
	NAME = NS.example.org 
	TYPE = A
	ADDRESS = 192.168.1.40
AUTHORITY section
	NAME = example.org
	TYPE = NS
	NSDNAME = NS.example.org
ADDITIONAL section
	NAME = NS.example.org
	TYPE = A
	ADDRESS = 192.168.1.40

*Should not include additional section. 
(Because ANSWER section's RR and ADDITIONAL section's RR overlap)
so, correct answer is like following.

----Correct Answer1 (for example 1)---
Question section
	QNAME = NS.example.org
	QTYPE = A
ANSWER section
	NAME = NS.example.org 
	TYPE = A
	ADDRESS = 192.168.1.40
AUTHORITY section
	NAME = example.org
	TYPE = NS
	NSDNAME = NS.example.org

-------example 2----------- 
Question section
	QNAME = example.org
	QTYPE = NS
ANSWER section
	NAME = example.org 
	TYPE = NS
	NSDNAME = NS.example.org
AUTHORITY section
	NAME = example.org
	TYPE = NS
	NSDNAME = NS.example.org
ADDITIONAL section
	NAME = NS.example.org
	TYPE = A
	ADDRESS = 192.168.1.40

*Should not include authority section. 
(Because ANSWER section's RR and AUTHORITY section's RR overlap)
so, correct answer is like following.

----Correct Answer2 (for example 2)---
Question section
	QNAME = example.org
	QTYPE = NS
ANSWER section
	NAME = example.org 
	TYPE = NS
	NSDNAME = NS.example.org
ADDITIONAL section
	NAME = NS.example.org
	TYPE = A
	ADDRESS = 192.168.1.40

Is my understanding correct?
Please teach me.

Best Regards,
-- 
*************************************
Hideshi Enokihara
IPv6 Business
Network & Software Development Dept.
Yokogawa Electric Corporation

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