Re: [dnsext] draft-mohan-dns-query-xml-00.txt

Paul Vixie <vixie@isc.org> Tue, 04 October 2011 22:30 UTC

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From: Paul Vixie <vixie@isc.org>
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Subject: Re: [dnsext] draft-mohan-dns-query-xml-00.txt
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On Tuesday, October 04, 2011 12:55:24 Måns Nilsson wrote:

> > >You can't increase the DNS message size beyond 64KB.
> > 
> > I was under the (mis) apprehension that was a UDP limitation, and that
> > large AFXRs could exceed 64KB. Live and learn.
> 
> I've done AXFRen of 1/2 GB zones. Not practical, but doable. The 64K
> limit does not apply to AXFR, but, then again, AXFR is not like the
> other children...

an AXFR can have many messages, each will be 64KB or smaller, and no RRset is 
allowed to span a message.  this means among other things that no RRset can be 
larger than ~64KB.  the fact that RRsets larger than 64KB could also not be 
carried in a query (whether by TCP/53 or UDP/53) also enforces this 
constraint.