Subject: Re: A6/DNAME usage guidelines and limits

From: Derek Atkins <[email-masked]>
Date: 04 Apr 2002 12:14:15 -0500

Paul Vixie <[email-masked]> writes:

> > What happens if the A6 chain requires N hops, and I get the first
> > three and then fail?
> 
> then you lose, i guess.  the hope is that once this situation is widely
> known, then improved caching robustness will be seen by network operators
> as a key way to increase their overall network robustness.

Right.  The problem is that the client resolver has _half_ the data
and doesn't know when it will complete.  With AAAA (or A) you get a
response that is either 'yes' or 'no', not 'here is half your answer
-- look here for more information'.

> > I admit that this proposal does add complexity to the nameserver
> > implementation, because they must be aware of all A6 chains and "keep"
> > them in the cache..  Or, alternately, the nameserver must be required
> > to recurse on their own A6 records, even if they don't necessarily
> > recurse.
> 
> well, there's no way to require an authority server to fetch glue, though
> many will.

Sure there is:

"An A6 response MUST include the complete chain, or the response must
be SERVFAIL."

;-)

-derek
-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       [email-masked]                        PGP key available

--
to unsubscribe send a message to [email-masked] with
the word 'unsubscribe' in a single line as the message text body.
archive: <http://ops.ietf.org/lists/namedroppers/>

---

From: Robert Elz <[email-masked]>
Date: Fri, 05 Apr 2002 21:01:54 +0700

Date:        04 Apr 2002 12:14:15 -0500
    From:        Derek Atkins <[email-masked]>
    Message-ID:  <[email-masked]>

  | Right.  The problem is that the client resolver has _half_ the data
  | and doesn't know when it will complete.

The fact that it is half the data is irrelevant - if you allow yourself
to view it other than that way, then you'll see it is no different than
any other query.

  | With AAAA (or A) you get a
  | response that is either 'yes' or 'no', not 'here is half your answer
  | -- look here for more information'.

Of course you do - to fetch an answer (except in the case that you already
have the answer, and A6 is no different there), you have to go and send
queries, usually several queries.  To find NS records, to resolve CNAME
records, ...   All during that the answer is in the process of being
accumulated.   A6 is just the same - or if you like, just more of the
same.   During processing, records will be being fetched, eventually the
last RR arrives, and you're done.  Until then, you're just part way through
getting the data.

kre