Subject: another open question on AXFR clarify

From: Edward Lewis <[email-masked]>
Date: Mon, 16 Jun 2008 14:52:49 -0400

What happens if a client has an open connection to an old style 
server (one that does not fill in the query ID or the answer section) 
and issues a first axfr request.  Before the response finished, the 
client sends a second axfr request.

How do these old style servers react?  Do they ignore the request? 
Do they answer in a confusing manner (that is mashing the two 
responses together)?  Or are they so single threaded that the second 
query isn't processed at all before finishing the first?

I'm asking for as I am rewriting the sections on query ID.  As in, 
when does a client know it is talking to a new AXFR server (one that 
can manage to not mangle responses).
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Edward Lewis                                                +1-571-434-5468
NeuStar

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From: Mark Andrews <[email-masked]>
Date: Tue, 17 Jun 2008 10:48:52 +1000

> client sends a second axfr request.

	Remember old style servers just have a implementation bug
	in that they failed to set the ID on all messages in the
	response stream.  We clearly saw it as a bug when it was
	pointed out.  The fact that it wasn't picked up earlier was
	due to another bug (lack of checking of ID on the client
	side).

	Basic DNS design has the response id match the request id.
	This clearly was not happening so it was a bug.
 
> Do they ignore the request? 

	Some will.  Some versions of named forked to return AXFR
	so they only accepted one AXFR request as they couldn't
	be sure the server hadn't been updated.

> responses together)?

	Could happen if they are not aware they have the bug and
	they process multiple axfr requests on the one socket.

	named does not fall into this category.

> Or are they so single threaded that the second 

	Some will.

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Mark Andrews, ISC
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PHONE: +61 2 9871 4742                 INTERNET: [email-masked]