Subject: [Enum] Backward compatibility

From: Brandner Rudolf <[email-masked]>
Date: Tue, 12 Feb 2002 17:40:18 +0100

Hi folks,

let's assume that an end system (or terminal) sends out a DNS request with a NAPTR in it and this request hits an intermediate node still running an old version of BIND (i.e. BIND 5).

What will happen with that request?

Best Regards,
Rudi

Rudolf Brandner
Siemens ICN M SR 1
+49-89-72251003

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From: Patrik Fältström <[email-masked]>
Date: Wed, 13 Feb 2002 09:00:48 +0100

--On 2002-02-12 17.40 +0100 Brandner Rudolf
<[email-masked]> wrote:

> let's assume that an end system (or terminal) sends out a DNS request
> with a NAPTR in it and this request hits an intermediate node still
> running an old version of BIND (i.e. BIND 5).
> 

Executive summary:

There will not be any problem.

Detailed summary:

You have two different issues here, and then another one hidden in the
details:

(a) Can an old version of for example BIND be primary/master server for
NAPTR resource records?

- A DNS server software can only be primary/master for resource record
types which one can enter into the software. I.e. it have to do with
managment and administration.

(b) If you have a non-primary server, can it be a forwarding / caching only
server for resource record types it does not understand?

- Yes, a DNS program do according can handle DNS packets where the resource
record type is unknown.

And now the hidden one:

(c) Can Bind (explicitly) before version 8 be secondary server for a zone
which have unknown RR types?

- No, because the secondary server caches the zone info on disk, and it can
then not parse the output when it tries to read it after a reboot.

Note 1: NAPTR was introduced for some time ago, so I even think some
version 4 of Bind do handle NAPTR.

Note 2: If you run a DNS software which is older than a year, you have
other problems, namely security problems, regardless of who has written the
software.

Note 3: What is important to know is that the DNS specification itself
makes it possible to handle unknown RR types.

       paf