Re: [DNSOP] Clarifying referrals (#35)

Andrew Sullivan <ajs@anvilwalrusden.com> Wed, 29 November 2017 01:55 UTC

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From: Andrew Sullivan <ajs@anvilwalrusden.com>
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Subject: Re: [DNSOP] Clarifying referrals (#35)
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Yes, what I just sent.  So how does one end up in 3.b with the AA bit
and still have a "referral" according to 1034, section 4.3.2?

A

On Wed, Nov 29, 2017 at 12:49:48PM +1100, Mark Andrews wrote:
> AA              Authoritative Answer - this bit is valid in responses,
>                 and specifies that the responding name server is an
>                 authority for the domain name in question section.
> 
>                 Note that the contents of the answer section may have
>                 multiple owner names because of aliases.  The AA bit
>                 corresponds to the name which matches the query name, or
>                 the first owner name in the answer section.
> 
> > On 29 Nov 2017, at 12:46 pm, Mark Andrews <marka@isc.org> wrote:
> > 
> > GO READ STD13!
> > 
> >> On 29 Nov 2017, at 12:44 pm, Andrew Sullivan <ajs@anvilwalrusden.com> wrote:
> >> 
> >> Hi,
> >> 
> >> On Wed, Nov 29, 2017 at 07:39:42AM +1100, Mark Andrews wrote:
> >>> The AA bit may or may not be set depending upon whether the response contains
> >>> a CNAME/DNAME or not.  
> >>> 
> >> 
> >> I replied with an enthusiastic "thanks" because this struck me as
> >> obviously correct, but then I though I'd better look at the algorithm
> >> again.  And now I have a problem.
> >> 
> >> 3.a is the CNAME case, but it's not a referral in the 1035 sense.
> >> 
> >> 3.b takes us out of the authoritative data, so AA should not be set.
> >> 
> >> Now, in RFC 6672 the DNAME processing happens at step 3.C, which
> >> undertakes the DNAME processing.  The resulting answer goes into the
> >> answer section and processing continues.
> >> 
> >> None of these steps seems to provide the case where a referral happens
> >> but the AA bit is set.  So, while I feel like I agree that in some
> >> cases the AA bit should be set and not clear in case the response
> >> contains a CNAME or DNAME, I'm trying to figure out whether such
> >> responses are really referrals or else just intermediate steps. RFC
> >> 6672 doesn't call them referrals.  Maybe this is a bit of informal
> >> jargon that needs clarifying?
> >> 
> >> Thanks for the contribution, and best regards,
> >> 
> >> A
> >> 
> >>>> On 29 Nov 2017, at 6:50 am, Andrew Sullivan <ajs@anvilwalrusden.com> wrote:
> >>>> 
> >>>> Dear colleagues,
> >>>> 
> >>>> Joe Abley and I have just submitted a draft
> >>>> (https://datatracker.ietf.org/doc/draft-sullivan-dnsop-refer-down/)
> >>>> that is intended to capture the discussion here about referrals and
> >>>> how to describe them.  It is intended for BCP, and it discourages
> >>>> upward referrals by authoritative servers.
> >>>> 
> >>>> That leaves the task of the referrals definition.  I have some new
> >>>> text below:
> >>>> 
> >>>> ---%<---cut here---
> >>>> 
> >>>> Referral: A type of response in which a server, signalling that it is
> >>>> not authoritative for an answer, provides the querying resolver with
> >>>> an alternative place to send its query.  A referral contains an empty
> >>>> answer section.  It contains the NS RRset for the referred-to zone in
> >>>> the authority section.  It may contain RRs that provide addresses in
> >>>> the additional section.  The AA bit is clear.
> >>>> 
> >>>> There are two types of referral response.  The first is a downward
> >>>> referral (sometimes described as "delegation response"), where the
> >>>> server is authoritative for some portion of the QNAME.  The Authority
> >>>> section RRset's RDATA contains the name servers specified at the
> >>>> referred-to zone cut.  In normal DNS operation, this kind of response
> >>>> is required in order to find names beneath a delegation.
> >>>> 
> >>>> The second is an upward referral (sometimes described as "root
> >>>> referral" or just "referral response", as distinct from the delegation
> >>>> response above), where the server is not authoritative for any portion
> >>>> of the QNAME.  When this happens, the referred-to zone in the
> >>>> Authority section is usually the root zone (.).  In normal DNS
> >>>> operation, this kind of response is not strictly speaking required to
> >>>> work, and in practice some authoritative server operators will not
> >>>> return referral responses beyond those required for delegation.
> >>>> 
> >>>> [optional: see draft-sullivan-dnsop-refer-down-00 or whatever.  We'll
> >>>> only include this reference if the other draft reaches WG consensus
> >>>> before terminology-bis]
> >>>> 
> >>>> ---cut here--->%---
> >>>> 
> >>>> Comments, please.  Also, Joe and I solicit comments on the referrals
> >>>> draft proper, but it would be nice to put that in a different thread.
> >>>> 
> >>>> Best regards,
> >>>> 
> >>>> A
> >>>> 
> >>> 
> >> 
> > 
> 

-- 
Andrew Sullivan
ajs@anvilwalrusden.com