Re: [dnsext] I-D Action: draft-ietf-dnsext-rfc2671bis-edns0-08.txt

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Hi Dave,

On 02/24/2012 04:10 PM, Dave Lawrence wrote:
> W.C.A. Wijngaards writes:
>> Could the authors put text in 6.1.1: The OPT record is normally
>> placed near the end of the additional section.
>> 
>> Because then there is guidance for the 'normal case'.
> 
> Given the interest in trying to have an EDNS-capable server
> include the OPT whenever possible, I'd recommend that the guidance
> be for the record to be first.
> 
> I'd actually thought that was what earlier drafts said, but going
> back to them I see they didn't do it explicitly and I only inferred
> it because the simplest algorithm for building the reply would be
> "add the OPT if it fits, then add any other records until you run
> out of room."  There are, of course, other ways of doing it, but
> providing guidance that it be first emphasizes the idea that the
> OPT is the one Additional RR that we really want to be present if
> at all possible.

Yes, you want EDNS OPT to be present if at all possible.
No, not at the start of the additional section, it is near the end of
the additional section.  The idea is that you reserve some space at
the end of the packet for the EDNS OPT record.  Then, you try to fit
as much additional-section data and so forth as you want into the
remaining space that is available.

I do not think 'first' is backwards compatible.

Best regards,
   Wouter
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