Subject: Re: [dnsext] axfr-clarify-10 section 3.2, Delegation Records

From: "W.C.A. Wijngaards" <[email-masked]>
Date: Tue, 03 Feb 2009 13:15:04 +0100

+1  (if +1s are appreciated).

Andreas Gustafsson wrote:
> The quoted paragraph appears to be a somewhat mangled version of text
> I suggested.  Perhaps the following would be clearer:
> 
>     4) This requirement is necessary to ensure that retrieving a given
>     (zone,serial) pair by AXFR yields the exact same set of resource
>     records no matter which of the zone's authoritative servers is
>     chosen as the source of the transfer.
> 
>     If an AXFR server were allowed to respond with the authoritative
>     NS RRset of a child zone instead of a glue NS RRset in the zone
>     being transferred, the set of records returned could vary depending
>     on whether or not the server happens to also be authoritative for 
>     the child zone.
> 
>     The property that a given (zone,serial) pair corresponds to a
>     single, well-defined set of records is necessary for the correct
>     operation of incremental transfer protocols such as IXFR
>     [RFC1995].  For example, a client may retrieve a zone by AXFR from
>     one server, and then apply an incremental change obtained by IXFR
>     from a different server.  If the two servers have different ideas
>     of the zone contents, the client can end up attempting to
>     incrementally add records that already exist or to delete records
>     that do not exist.
> 

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From: Edward Lewis <[email-masked]>
Date: Tue, 3 Feb 2009 16:25:21 -0500

>+1  (if +1s are appreciated).

Editors always appreciate +1's ;)
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From: Mark Andrews <[email-masked]>
Date: Wed, 04 Feb 2009 08:49:15 +1100

> Editors always appreciate +1's ;)

For the record there are also non IXFR related examples where the
the master of the parent zone is a slave of the child zone and the
other parents don't the changes added to the parent zone as the
child zone has not yet transferred.

Possible cause: email notifying parent arrives before refresh timer
	 goes off.

Mark
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Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: [email-masked]